,a ,,history ,,of ,,land ,,mammals ,,in ,,the ,,western ,,hemisphere ,illustration ,,the ,,macmillan ,,company ,,new ,,york ,,boston ,,chicago ,,dallas ,,atlanta ,,san ,,francisco ,,macmillan ,,co41 ,,limited ,,london ,,bombay ,,calcutta ,,melbourne ,,the ,,macmillan ,,co4 ,,of ,,canada1 ,,ltd4 ,,toronto ,illustration3 ,,frontispiece4--,a ,pleistocene tar-pool in southern ,california3 ,giant ,wolves 7,canis dirus7 and ,sabre-tooth ,tiger 7,smilodon californicus7 on the carcass of an elephant 7,elephas columbi74 ,the elephant is hairless1 as may have been true of the southern race4 ,a ,,history ,,of ,,land ,,mammals ,,in ,,the ,,western ,,hemisphere ,,by ,,william ,b4 ,,scott ,,ph4,d4 7,heidelberg71 ,,hon4,d4,,sc4 7,harvard ,oxford71 ,,ll4,d4 7,univ4 of ,pennsylvania7 ,,blair ,,professor ,,of ,,geology ,,and ,,pal,,ontology ,,in ,,princeton ,,university ,,illustrated ,,with #cb ,,plates ,,and ,,more ,,than #ajj ,,drawings ,,by ,,bruce ,,horsfall ,new ,york ,,the ,,macmillan ,,company #aiac ,all rights reserved ,,copyright1 #aiac1 ,,by ,,the ,,macmillan ,,company4 ,set up and electrotyped4 ,published ,november1 #aiac4 ,norwood ,press ,j4 ,s4 ,cushing ,co4--,berwick ,smith ,co4 ,norwood1 ,mass41 ,u4,s4,a4 ,dedicated ,,to ,,my ,,classmates ,,henry ,,fairfield ,,osborn ,,and ,,francis ,,speir ,,in ,,memory ,,of ,a ,,notable ,,summer ,,afternoon ,,in #ahgf ,,and ,,in ,,token ,,of ,,forty ,,years' ,,unclouded ,,friendship ,speak to the earth and it shall teach thee4 --,,job1 xii1 #h4 ,can these bones live8 --,,ezekiel1 xxxvii1 #c4 ,,preface ,one afternoon in ,june1 #ahgf1 three ,princeton undergraduates were lying under the trees on the canal bank1 making a languid pretence of preparing for an examination4 ,suddenly1 one of the trio remarked3 8,i have been reading an old magazine article which describes a fossil-collecting expedition in the ,west2 why can't we get up something of the kind80 ,the others replied1 as with one voice1 8,we can2 let's do it40 ,this seemingly idle talk was1 for ,osborn and myself1 a momentous one1 for it completely changed the careers which1 as we then believed1 had been mapped out for us4 ,the random suggestion led directly to the first of the ,princeton palontological expeditions1 that of #ahgg1 which took us to the 8,bad ,lands0 of the ,bridger region in southwestern ,wyoming4 ,the fascination of discovering and exhuming with our own hands the remains of the curious creatures which once inhabited ,north ,america1 but became extinct ages ago1 has proved an enduring delight4 ,it was the wish to extend something of this fascinating interest to a wider circle1 that occasioned the preparation of this book4 ,the western portion of ,north ,america has preserved a marvellous series of records of the successive assemblages of animals which once dwelt in this continent1 and in southernmost ,south ,america an almost equally complete record was made of the strange animals of that region4 ,for the last half-century1 or more1 many workers have coperated to bring this long-vanished world to light and to decipher and interpret the wonderful story of mammalian development in the western hemisphere4 ,the task of making this history intelligible1 not to say interesting1 to the layman1 has been one of formidable difficulty1 for it is recorded in the successive modifications of the bones and teeth1 and without some knowledge of osteology1 these records are in an unknown tongue4 ,to meet this need1 ,chapter ,,iii gives a sketch of the mammalian skeleton and dentition1 which the reader may use as the schoolboy uses a vocabulary to translate his ,latin exercise1 referring to it from time to time1 as may be necessary to make clear the descriptions of the various mammalian groups4 ,technical terms have been avoided as far as possible1 but1 unfortunately1 it is not practicable to dispense with them altogether4 ,the appended glossary will1 it is hoped1 minimize the inconvenience4 ,no one who has not examined it1 can form any conception of the enormous mass and variety of material1 illustrating the history of ,american mammals1 which has already been gathered into the various museums4 ,a full account of this material would require many volumes1 and one of the chief problems in the preparation of this book has been that of making a proper selection of the most instructive and illuminating portions of the long and complicated story4 ,indeed1 so rapid is the uninterrupted course of discovery1 that parts of the text became antiquated while in the press and had to be rewritten4 ,as first prepared1 the work proved to be far too long and it was necessary to excise several chapters1 for it seemed better to cover less ground than to make the entire history hurried and superficial4 ,the plan of treatment adopted involves a considerable amount of repetition1 but this is perhaps not a disadvantage1 since the same facts are considered from different points of view4 ,the facts which are here brought together have been ascertained by many workers1 and ,i have borrowed with the greatest freedom from my fellow labourers in the field of palontology4 ,as every compiler of a manual finds1 it is not feasible to attribute the proper credit to each discoverer4 ,huxley has so well explained the situation in the preface to his 8,anatomy of ,vertebrated ,animals10 that ,i may be permitted to borrow his words3 8,i have intentionally refrained from burdening the text with references2 and1 therefore1 the reader1 while he is justly entitled to hold me responsible for any errors he may detect1 will do well to give me no credit for what may seem original1 unless his knowledge is sufficient to render him a competent judge on that head40 ,a book of this character is obviously not the proper place for polemical discussions of disputed questions4 ,whenever1 therefore1 the views expressed differ widely from those maintained by other palontologists1 ,i have attempted no more than to state1 as fairly as ,i could1 the alternative interpretations and my own choice between them4 ,any other course was forbidden by the limitations of space4 ,it is a pleasure to give expression to my sincere sense of gratitude to the many friends who have helped me in an unusually laborious undertaking4 ,professor ,osborn and ,dr4 ,matthew have placed at my disposal the wonderful treasures of the ,american ,museum of ,natural ,history in ,new ,york and in the most liberal manner have supplied me with photographs and specimens for drawings1 as well as with information regarding important discoveries which have not yet been published4 ,dr4 ,w4 ,j4 ,holland1 ,director of the ,carnegie ,museum in ,pittsburgh1 has likewise generously provided many photographs from the noble collection under his charge1 kindly permitting the use of material still undescribed4 ,to ,professor ,charles ,schuchert1 of ,yale ,university1 ,i am also indebted for several photographs4 ,the figures of existing animals are almost all from photographs taken in the ,new ,york and ,london zological gardens1 and ,i desire to thank ,director ,hornaday1 of the ,bronx ,park1 and ,mr4 ,peacock1 of the ,london garden1 for the very kind manner in which they have procured these illustrations for my use4 ,the photographs have been modified by painting out the backgrounds of cages1 houses1 and the like1 so as to give a less artificial appearance to the surroundings4 ,to my colleagues at ,princeton ,i am under great obligations for much valuable counsel and assistance4 ,professor ,gilbert van ,ingen has prepared the maps and diagrams and ,dr4 ,w4 ,j4 ,sinclair has devoted much labour and care to the illustrations and has also read the proofs4 ,both of these friends1 as also ,professors ,c4 ,h4 ,smyth and ,e4 ,g4 ,conklin and ,drs4 ,farr and ,mc,comas1 have read various parts of the manuscript and made many helpful suggestions in dealing with the problems of treatment and presentation4 ,for thirteen years past ,i have been engaged in the study of the great collections of fossil mammals1 gathered in ,patagonia by the lamented ,mr4 ,hatcher and his colleague1 ,mr4 ,peterson1 now of the ,carnegie ,museum4 ,this work made it necessary for me to visit the museums of the ,argentine ,republic1 which ,i did in #aija1 and was there received with the greatest courtesy and kindness by ,dr4 ,f4 ,moreno1 ,director1 and ,dr4 ,santiago ,roth1 of the ,la ,plata ,museum1 and ,dr4 ,f4 ,ameghino1 subsequently ,director of the ,national ,museum at ,buenos ,aires4 ,to all of these gentlemen the chapters on the ancient life of ,south ,america are much indebted1 especially to ,dr4 ,ameghino1 whose untimely death was a great loss to science4 ,it is earnestly to be hoped that the heroic story of his scientific career may soon be given to the world4 ,finally1 ,i desire to thank ,mr4 ,horsfall for the infinite pains and care which he has expended upon the illustrations for the work1 to which so very large a part of its value is due4 ,while the book is primarily intended for the lay reader1 ,i cannot but hope that it may also be of service to many zologists1 who have been unable to keep abreast of the flood of palontological discovery and yet wish to learn something of its more significant results4 ,how far ,i have succeeded in a most difficult task must be left to the judgment of such readers4 ,,princeton1 ,n4,j41 ,june #a1 #aiac4 ,,contents ,,page ,,chapter ,i ,,methods ,,of ,,investigation--,,geological #a ,,chapter ,,ii ,,methods ,,of ,,investigation--,,pal,,ontological #bi ,,chapter ,,iii ,,the ,,classification ,,of ,,the ,,mammalia #ej ,,chapter ,,iv ,,the ,,skeleton ,,and ,,teeth ,,of ,,mammals #fa ,,chapter ,v ,,the ,,geographical ,,development ,,of ,,the ,,americas ,,in ,,cenozoic ,,times #ii ,,chapter ,,vi ,,the ,,geographical ,,distribution ,,of ,,mammals #ace ,,chapter ,,vii ,,the ,,successive ,,mammalian ,,faunas ,,of ,,north ,,and ,,south ,,america #aib ,,chapter ,,viii ,,history ,,of ,,the ,,perissodactyla #bhh ,,chapter ,,ix ,,history ,,of ,,the ,,artiodactyla #ceh ,,chapter ,x ,,history ,,of ,,the ,,proboscidea #dbb ,,chapter ,,xi ,,history ,,of ,,the ,,amblypoda ,,and ,,condylarthra #ddc ,,chapter ,,xii ,,history ,,of ,,the ,,toxodontia 7,,or ,,notoungulata7 #dfa ,,chapter ,,xiii ,,history ,,of ,,the ,,litopterna ,,and ,,astrapotheria #dhi ,,chapter ,,xiv ,,history ,,of ,,the ,,carnivora #eaf ,,chapter ,,xv ,,history ,,of ,,the ,,primates #egg ,,chapter ,,xvi ,,history ,,of ,,the ,,edentata #ehi ,,chapter ,,xvii ,,history ,,of ,,the ,,marsupialia #fbd ,,chapter ,,xviii ,,modes ,,of ,,mammalian ,,evolution #fde ,,glossary #ffe ,,index #fge ,a ,,history ,,of ,,land ,,mammals ,,in ,,the ,,western ,,hemisphere ,,chapter ,i ,,methods ,,of ,,investigation--,,geological ,the term ,mammal has no exact equivalent in the true vernacular of any modern language1 the word itself1 like its equivalents1 the ,french ,mammifre and the ,german ,sugethier1 being entirely artificial4 ,as a name for the class ,linnus adopted the term ,mammalia1 which he formed from the ,latin mamma 7i4e4 teat7 to designate those animals which suckle their young2 hence the abbreviated form ,mammal1 which has been naturalized as an ,english word4 8,beast10 as employed in the ,bible1 and 8,quadruped0 are not quite the same as mammal1 for they do not include the marine forms1 such as whales1 dolphins1 seals1 walruses1 or the flying bats1 and they are habitually used in contradistinction to ,man1 though ,man and all the forms mentioned are unquestionably mammals4 ,in attempting to frame a definition of the term ,mammal1 it is impossible to avoid technicalities altogether1 for it is the complete unity of plan and structure which justifies the inclusion of all the many forms that differ so widely in habits and appearance4 ,mammals are air-breathing vertebrates1 which are warm-blooded and have a #d-;chambered heart2 the body cavity is divided into pleural and abdominal chambers by a diaphragm2 except in the lowest division of the class1 the young are brought forth alive and are always suckled1 the milk glands being universal throughout the class4 ,in the great majority of mammals the body is clothed with hair2 a character found in no other animals4 ,in a few mammals the skin is naked1 and in still fewer there is a partial covering of scales4 ,the list of characters common to all mammals1 which distinguish them from other animals1 might be indefinitely extended1 for it includes all the organs and tissues of the body1 the skeletal1 muscular1 digestive1 nervous1 circulatory1 and reproductive systems1 but the two or three more obvious or significant features above selected will suffice for the purposes of definition4 ,while the structural plan is the same throughout the entire class1 there is among mammals a wonderful variety of form1 size1 appearance1 and adaptation to special habits4 ,it is as though a musician had taken a single theme and developed it into endless variations1 preserving an unmistakable unity through all the changes4 ,most mammals are terrestrial1 living1 that is to say1 not only on the land1 but on the ground1 and are herbivorous in habit1 subsisting chiefly or exclusively upon vegetable substances1 but there are many departures from this mode of life4 ,it should be explained1 however1 that the term terrestrial is frequently used in a more comprehensive sense for all land mammals1 as distinguished from those that are aquatic or marine4 ,monkeys1 ,squirrels1 ,sloths and ,opossums are examples of the numerous arboreal mammals1 whose structure is modified to fit them for living and sleeping in the trees1 and in some1 such as the ,sloths1 the modification is carried so far that the creature is almost helpless on the ground4 ,another mode of existence is the burrowing or fossorial1 the animal living partly or mostly1 or even entirely underground1 a typical instance of which is the ,mole4 ,the ,beaver1 ,muskrat and ,otter1 to mention only a few forms1 are aquatic and spend most of their life in fresh waters1 though perfectly able to move about on the land4 ,marine mammals1 such as the ,seals and ,whales1 have a greatly modified structure which adapts them to life in the sea4 ,within the limits of each of these categories we may note that there are many degrees of specialization or adaptation to particular modes of life4 ,thus1 for example1 among the marine mammals1 the ,whales and their allies1 ,porpoises1 etc41 are so completely adapted to a life in the seas that they cannot come upon the land1 and even stranding is fatal to them1 while the ,seals frequently land and move about upon the shore4 ,it should further be observed that mammals of the most diverse groups are adapted to similar modes of existence4 ,thus in one natural group or order of related forms1 occur terrestrial1 burrowing1 arboreal and aquatic members1 and the converse statement is of course equally true1 that animals of similar life-habits are not necessarily related to one another1 and very frequently1 in fact1 are not so related4 ,among the typically marine mammals1 for example1 there are at least three and probably four distinct series1 which have independently become adapted to life in the sea4 99 99 99 99 99 ,before attempting to set forth an outline of what has been learned regarding the history of mammalian life in the western hemisphere1 it is essential to give the reader some conception of the manner in which that knowledge has been obtained4 ,without such an understanding of the methods employed in the investigation the reader can only blindly accept or as blindly reject what purports to be the logical inference from well-established evidence4 ,how is that evidence to be discovered8 and how may trustworthy conclusions be derived from it8 ,the first and most obvious step is to gather all possible information concerning the mammals of the present day1 their structure 7comparative anatomy71 functions 7physiology71 and their geographical arrangement4 ,this latter domain1 of the geographical distribution of mammals1 is one of peculiar significance4 ,not only do the animals of ,north ,america differ radically from those of ,central and ,south ,america1 but within the limits of each continent are more or less well-defined areas1 the animals of which differ in a subordinate degree from those of other areas4 ,the study of the modern world1 however1 would not of itself carry us very far toward the goal of our inquiries1 which is an explanation1 not merely a statement1 of the facts4 ,the present order of things is the outcome of an illimitably long sequence of events and can be understood only in proportion to our knowledge of the past4 ,in other words1 it is necessary to treat the problems involved in our inquiry historically2 to trace the evolution of the different mammalian groups from their simpler beginnings to the more complex and highly specialized modern forms2 to determine1 so far as that may be done1 the place of origin of each group and to follow out their migrations from continent to continent4 ,while we shall deal chiefly1 almost exclusively1 with the mammals of the ,new ,world1 something must be said regarding those of other continents1 for1 as will be shown in the sequel1 both ,north and ,south ,america have1 at one time or another1 been connected with various land-masses of the eastern hemisphere4 ,by means of those land-connections1 there has been an interchange of mammals between the different continents1 and each great land-area of the recent world contains a more or less heterogeneous assemblage of forms of very diverse places of origin4 ,indeed1 migration from one region to another has played a most important part in bringing about the present distribution of living things4 ,from what has already been learned as to the past life of the various continents and their shifting connections with one another1 it is now feasible to analyze the mammalian faunas of most of them and to separate the indigenous from the immigrant elements4 ,among the latter may be distinguished those forms which are the much modified descendants of ancient migrants from those which arrived at a much later date and have undergone but little change4 ,to take a few examples from ,north ,america1 it may be said that the ,bears1 ,moose1 ,caribou and ,bison are late migrants from the ,old ,world2 that the ,virginia and ,black-tailed ,deer and the ,prong-horned ,antelope are of ,old ,world origin1 but their ancestors came in at a far earlier period and the modern species are greatly changed from the ancestral migrants4 ,the ,armadillo of ,texas and the ,canada ,porcupine are almost the only survivors1 north of ,mexico1 of the great migration of ,south ,american mammals which once invaded the northern continent4 ,on the other hand1 the raccoons and several families of rodents are instances of indigenous types which may be traced through a long ,american ancestry4 ,fully to comprehend the march of mammalian development1 it thus becomes necessary to reconstruct1 at least in outline1 the geography of the successive epochs through which the developmental changes have taken place1 the connections and separations of land-masses1 the rise of mountain ranges1 river and lake systems and the like4 ,equally significant factors in the problem are climatic changes1 which have had a profound and far-reaching effect upon the evolution and geographical spread of animals and plants1 and the changes in the vegetable world must not be ignored1 for1 directly or indirectly1 animals are dependent upon plants4 ,to one who has paid no attention to questions of this kind1 it might well seem an utterly hopeless task to reconstruct the long vanished past1 and he would naturally conclude that1 at best1 only fanciful speculations1 with no foundation of real knowledge1 could be within our reach4 ,happily1 such is by no means the case4 ,geology offers the means of a successful attack upon these problems and1 although very much remains to be done1 much has already been accomplished in elucidating the history1 especially in its later periods1 with which the story of the mammals is more particularly concerned4 ,it is manifestly impossible to present here a treatise upon the science of ,geology1 even in outline sketch4 ,considerations of space are sufficient to forbid any such attempt4 ,certain things must be taken for granted1 the evidence for which may be found in any modern text-book of ,geology4 ,for example1 it is entirely feasible to establish the mode of formation of almost any rock 7aside from certain problematical rocks1 which do not enter into our discussion7 and to determine whether it was laid down in the sea1 or on the land1 or in some body of water not directly connected with the sea1 such as a lake or river4 ,with the aid of the microscope1 it is easy to discriminate volcanic material from the ordinary water-borne and wind-borne sediments and1 in the case of the rocks which have solidified from the molten state1 to distinguish those masses which have cooled upon the surface from those which have solidified deep within the earth4 ,while the nature and mode of formation of the rocks may thus be postulated1 it will be needful to explain at some length the character of the evidence from which the history of the earth may be deciphered4 ,first of all1 must be made clear the method by which the events of the earth's history may be arranged in chronological order1 for a history without chronology is unintelligible4 ,the events which are most significant for our purpose are recorded in the rocks which are called stratified1 bedded or sedimentary1 synonymous terms4 ,such rocks were made mostly from the dbris of older rocks1 in the form of gravel1 sand or mud1 and were laid down under water1 or1 less extensively1 spread by the action of the wind upon a land-surface4 ,important members of this group of rocks are those formed1 more or less completely1 from the finer fragments given out in volcanic eruptions1 carried and sorted by the wind and finally deposited1 it may be at great distances from their point of origin1 upon a land-surface1 or on the bottom of some body of water4 ,stratified or bedded rocks1 as their name implies1 are divided into more or less parallel layers or beds1 which may be many feet or only a minute fraction of an inch in thickness4 ,such a division means a pause in the process of deposition or a change in the character of the material deposited over a given area4 ,owing to the operation of gravity1 the layers of sediment are spread out in a horizontal attitude1 which disregard the minor irregularities of the bottom1 just as a deep snow buries the objects which lie upon the surface4 ,a moment's consideration will show that1 in any series of stratified rocks which have not been greatly disturbed from their original horizontal position1 the order of succession or superposition of the beds must necessarily be the chronological order of their formation4 7,fig4 #a47 ,obviously1 the lowest beds must have been deposited first and therefore are the oldest of the series1 while those at the top must be the newest or youngest and the beds intermediate in position are intermediate in age4 ,this inference depends upon the simple principle that each bed must have been laid down before the next succeeding one can have been deposited upon it4 ,while this is so clear as to be almost self-evident1 it is plain that such a mode of determining the chronological order of the rocks of the earth's crust can be of only local applicability and so far as the beds may be traced in unbroken continuity4 ,it is of no direct assistance in correlating the events in the history of one continent with those of another and it fails even in comparing the distinctly separated parts of the same continent4 ,some method of universal applicability must be devised before the histories of scattered regions can be combined to form a history of the earth4 ,such a universal method is to be found in the succession of the forms of life1 so far as that is recorded in the shape of fossils1 or the recognizable remains of animal and vegetable organisms preserved in the rocks4 ,illustration3 ,,fig4 #a4--;,diagram section of a series of beds1 illustrating superposition4 ,a is the oldest1 ,b1 ,c1 ,d1 etc41 succeeding in ascending order4 ,this principle was first enunciated by ,william ,smith1 an ,english engineer1 near the close of the eighteenth century1 who thus laid the foundations of ,historical ,geology4 ,in the diagram1 ,fig4 #b1 is reproduced ,smith's section across ,england from ,wales to near ,london1 which shows the successive strata or beds1 very much tilted from their original horizontal position by the upheaval of the sea-bed upon which they were laid down4 ,the section pictures the side of an imaginary gigantic trench cut across the island and was constructed by a simple geometrical method from the surface exposures of the beds1 such as mining engineers continually employ to map the underground extension of economically important rocks1 and shows how an enormous thickness of strata may be studied from the surface4 ,the older beds are exposed at the western end of the section in ,wales and1 passing eastward1 successively later and later beds are encountered1 the newest appearing at the eastern end4 ,very many of the strata are richly fossiliferous1 and thus a long succession of fossils was obtained in the order of their appearance1 and this order has been found to hold good1 not only in ,england1 but throughout the world4 ,the order of succession of the fossils was thus in the first instance actually ascertained from the succession of the strata in which they are found and has been verified in innumerable sections in many lands and is thus a matter of observed and verifiable fact1 not merely a postulate or working hypothesis4 ,once ascertained1 however1 the order of succession of living things upon the earth may be then employed as an independent and indispensable means of geologically dating the rocks in which they occur4 ,illustration3 ,,fig4 #b4--,william ,smith's section across the south of ,england4 ,the vertical scale is exaggerated1 which makes the inclination of the beds appear too steep4 ,n4 ,b4 ,the original drawing is in colors1 which are not indicated by the dotted strata4 ,this is the palontological method1 which finds analogies in many other branches of learned inquiry4 ,the student of manuscripts discovers that there is a development1 or regular series of successive changes1 in handwriting1 and from the handwriting alone can make a very close approximation to the date of a manuscript4 ,the order in which those changes came about was ascertained from the comparative study of manuscripts1 the date of which could be ascertained from other evidence1 but1 when once established1 the changes in handwriting are used to fix the period of undated manuscripts4 ,just so1 the succession of fossils1 when learned from a series of superposed beds1 may then be employed to fix the geological date of strata in another region4 ,similarly1 the archologist has observed that there is an evolution or development in every sort of the work of men's hands and therefore makes use of coins1 inscriptions1 objects of art1 building materials and methods1 etc41 to date ancient structures4 ,in the ,german town of ,trier 7or ,trves7 on the ,moselle1 the cathedral has as a nucleus a ,roman structure1 the date and purpose of which had long been matters of dispute1 though the general belief was that the building had been erected under ,constantine the ,great4 ,in the course of some repairs made not very long ago1 it became necessary to cut deep into the ,roman brickwork1 and there1 embedded in the undisturbed mortar1 was a coin of the emperor ,valentinian ,,ii1 evidently dropped from the pocket of some ,roman bricklayer4 ,that coin fixed a date older than which the building cannot be1 though it may be slightly later1 and it well illustrates the service rendered by fossils in determining geological chronology4 ,other methods of making out the chronology of the earth's history have been proposed from time to time and all of them have their value1 though none of them renders us independent of the use of fossils1 which have the pre-eminent advantage of not recurring or repeating themselves at widely separated intervals of time1 as all physical processes and changes do4 ,an organism1 animal or plant1 that has become extinct never returns and is not reproduced in the evolutionary process4 ,great and well founded as is our confidence in fossils as fixing the geological date of the rocks in which they occur1 it must not be forgotten that the succession of the different kinds of fossils in time was first determined from the superposition of the containing strata4 ,hence1 it is always a welcome confirmation of the chronological inferences drawn from the study of fossils1 when those inferences can be unequivocally established by the succession of the beds themselves4 ,for example1 in the ,tertiary deposits of the ,west are two formations or groups of strata1 called respectively the ,uinta and the ,white ,river1 which had never been known to occur in the same region and whose relative age therefore could not be determined by the method of superposition4 ,each of the formations1 however1 has yielded a large number of well-preserved fossil mammals1 and the comparative study of these mammals made it clear that the ,uinta must be older than the ,white ,river and that no very great lapse of time1 geologically speaking1 occurred between the end of the former and the beginning of the latter4 ,only two or three years ago an expedition from the ,american ,museum of ,natural ,history discovered a place in ,wyoming where the ,white ,river beds lie directly upon those of the ,uinta1 thus fully confirming the inference as to the relative age of these two formations which had long ago been drawn from the comparative study of their fossil mammals4 ,the palontological method of determining the geological date of the stratified rocks is thus an indispensable means of correlating the scattered exposures of the strata in widely separated regions and in different continents1 it may be with thousands of miles of intervening ocean4 ,the general principle employed is that close similarity of fossils in the rocks of the regions compared points to an approximately contemporaneous date of formation of those rocks4 ,this principle must not1 however1 be applied in an off-hand or uncritical manner1 or it will lead to serious error4 ,in the first place1 the evolutionary process is a very slow one and geological time is inconceivably long1 so that deposits which differ by some thousands of years may yet have the same or nearly the same fossils4 ,the method is not one of sufficient refinement to detect such relatively small differences4 ,to recur to the illustration of the development in handwriting1 the palographer can hardly do more than determine the decade in which a manuscript was written2 no one would expect him to fix upon the exact year1 still less the month1 from the study of handwriting alone4 ,as is the month in recorded human history1 so is the millennium in the long course of the earth's development4 ,illustration3 ,,fig4 #c4--;,bluff on ,beaver ,creek1 ,fremont ,co41 ,wyoming4 ,the ,white ,river beds were deposited on the worn and weathered surface of the ,uinta1 the heavy1 broken line marking the separation between them4 ,the valley was carved out long after the deposition of the ,white ,river strata4 ,in the second place1 there are great differences in the contemporary life of separate regions and such geographical differences there have always been1 so far as we can trace back the history of animals and plants4 ,a new organism does not originate simultaneously all over the world but1 normally at least1 in a single area and spreads from that centre until it encounters insuperable obstacles4 ,such spreading is a slow process and hence it is that new forms often appear in one region much earlier than in others and in the very process of extending their range1 the advancing species may themselves be considerably modified and reach their new and distant homes as different species from those which originated the movement4 ,extinction1 likewise1 seldom occurs simultaneously over the range of a group1 but now here and now there in a way that to our ignorance appears to be arbitrary and capricious4 ,the process may go on until extinction is total1 or may merely result in a great restriction of the range of a given group1 or may break up that range into two or more distinct areas4 ,of such incomplete extinctions many instances might be given1 but one must suffice4 ,the camel-tribe1 strange as it may appear1 originated in ,north ,america and was long confined to that continent1 while at the present day it is represented only by the llamas of ,south ,america and the true camels of ,asia1 having completely vanished from its early home4 ,these facts and a host of similar ones make plain how necessary it is to take geographical considerations into account in all problems that deal with the synchronizing of the rocks of separate areas and continents4 ,properly to estimate the significance of a difference in the fossils of two regions and to determine how far it is geographical1 due to a separation in space1 or geological and caused by separation in time1 is often a very difficult matter and requires a vast amount of minute and detailed study4 ,once more1 the principle involved is illustrated by the study of manuscripts4 ,down to the time when the printing press superseded the copyist1 each of the nations of ,europe had its own traditions and its more or less independent course of handwriting development4 ,a great monastery1 in which the work of copying manuscripts went on century after century1 became an independent geographical centre with its particular styles4 ,thus the palographer1 like the geologist1 is confronted by geographical problems as well as by those of change and development in general4 ,in addition to the method of geologically dating the rocks by means of the fossils which they contain1 there are other ways which may give a greater precision to the result4 ,climatic changes1 when demonstrable1 are of this character1 for they may speedily and simultaneously affect vast areas of the earth's surface or even the entire world4 ,from time to time in the past1 glacial conditions have prevailed over immense regions1 several continents at once1 it may be1 as in one instance in which ,india1 ,south ,africa1 ,australia1 ,south ,america were involved4 ,the characteristic accumulations made by the glaciers in these widely separated regions must be contemporaneous in a sense that can rarely be predicated of the ordinary stratified rocks4 ,such climatic changes as the formation and disappearance of the ice-fields give a sharper and more definite standard of time comparisons than do the fossils alone1 and yet the fossils are in turn needed to show which of several possible glacial periods are actually being compared4 ,again1 great movements of the earth's crust1 which involve vast and widely separated regions and bring the sea in over great areas of land1 or raise great areas into land1 which had been submerged1 may also yield more precise time-measurements1 because occurring within shorter periods than do notable changes in the system of living things4 ,such changes in animals and plants may be compared to the almost imperceptible movement of the hour-hand of a clock1 while the recorded climatic revolutions and crustal movements often supply the place of the minute-hand4 ,it is obvious1 however1 that if the hour-hand be wanting1 the minute-hand alone can be of very limited use4 ,there have been a great many vast submergences and emergences of land in the history of the earth1 and only the fossils can give us the assurance that we are comparing the same movement in distant continents1 and not two similar movements separated by an enormous interval of time4 ,it may thus fairly be admitted that it is possible to arrange the rocks which compose the accessible parts of the earth's crust in chronological order and to correlate in one system the rocks of the various continents4 ,the terms used for the more important divisions of geological time are1 in descending order of magnitude1 era1 period1 epoch1 age or stage1 and the general scheme of the eras and periods1 which is in almost uniform use throughout the world1 is given in the table1 which is arranged so as to give the succession graphically1 with the most ancient rocks at the bottom and the latest at the top4 ,cenozoic era ,quaternary period ,tertiary period ,cretaceous period ,mesozoic era ,jurassic period ,triassic period ,permian period ,carboniferous period ,palozoic era ,devonian period ,silurian period ,ordovician period ,cambrian period ,pre-,cambrian eras ,algonkian period ,archan period ,it must not be supposed that all the divisions of similar rank1 such as the eras1 for example1 were of equal length1 as measured by the thickness of the rocks assigned to those divisions4 ,on the contrary1 they must have been of very unequal length and are of very different divisibility4 ,the ,pre-,cambrian eras1 with only two periods1 were probably far longer than all subsequent time1 and all that the major divisions imply is that they represent changes in the system of life of approximately equivalent importance4 ,it is impossible to give any trustworthy estimate of the actual lengths of these divisions in years1 though many attempts to do so have been made4 ,all that can be confidently affirmed is that geological time1 like astronomical distances1 is of inconceivable vastness and its years can be counted only in hundreds of millions4 ,to discuss in any intelligible manner the history of mammals1 it will be necessary to go much farther than the above table in the subdivision of that part of geological time in which mammalian evolution ran its course4 ,as mammals represent the highest stage of development yet attained in the animal world1 it is only the latter part of the earth's history which is concerned with them2 the earlier and incomparably longer portion of that history may be passed over4 ,mammals are first recorded in the later ,triassic1 the first of the three periods which make up the ,mesozoic era4 ,they have also been found1 though very scantily1 in the other ,mesozoic periods1 the ,jurassic and ,cretaceous1 but it was the ,cenozoic era that witnessed most of the amazing course of mammalian development and diversification1 and hence the relatively minute subdivisions necessary for the understanding of this history deal only with the ,cenozoic1 the latest of the great eras4 ,in the subjoined table the periods and epochs are those which are in general use throughout the world1 the ages and stages are those which apply to the western interior of ,north ,america1 each region1 even of the same continent1 requiring a different classification4 ,the ,south ,american formations are given in a separate table1 as it is desirable to avoid the appearance of an exactitude in correlation which cannot yet be attained4 ,,cenozoic ,,era ,quaternary period ,recent epoch ,pleistocene epoch ,glacial and ,interglacial stages4 ,pliocene epoch ,miocene epoch ,tertiary period ,oligocene epoch ,eocene epoch ,paleocene epoch ,continuing the subdivision of the ,tertiary period still farther1 we have the following arrangement3 ,,tertiary ,,period 7,north ,america7 ,upper ,wanting ,middle ,blanco age ,pliocene ,thousand ,creek age ,lower ,snake ,creek age ,republican ,river age ,upper ,loup ,fork age ,miocene ,middle ,deep ,river age ,lower ,arikaree age ,oligocene ,upper ,john ,day age ,lower ,white ,river age ,upper ,uinta age ,eocene ,middle ,bridger age ,lower ,wind ,river age ,wasatch age ,paleocene ,upper ,torrejon age ,fort ,union ,lower ,puerco age ,this is a representative series of the widespread and manifold non-marine ,tertiary deposits of the ,great ,plains1 but a much more extensive and subdivided scheme would be needed to show with any degree of fullness the wonderfully complete record of that portion of the continent during the ,tertiary period4 ,a much more elaborate table will be found in ,professor ,osborn's 8,age of ,mammals10 p4 #da4 ,there are some differences of practice among geologists as to this scheme of classification1 though the differences are not those of principle4 ,no question arises concerning the reality of the divisions1 or their order of succession in time1 but merely as to the rank or relative importance which should be attributed to some of them1 and that is a very minor consideration4 ,much greater difficulty and1 consequently1 much more radical differences of interpretation arise when the attempt is made to correlate or synchronize the smaller subdivisions1 as found in the various continents1 with one another1 because of the geographical differences in contemporary life4 ,between ,europe and ,north ,america there has always been a certain proportion of mammalian forms in common1 a proportion that was at one time greater1 at another less1 and this community renders the correlation of the larger divisions of the ,tertiary in the two continents comparatively easy1 and even in the minor subdivisions very satisfactory progress has been made1 so that it is possible to trace in some detail the migrations of mammals from the eastern to the western hemisphere and vice versa4 ,such intermigrations were made possible by the land-bridges connecting ,america with ,europe across the ,atlantic1 perhaps on the line of ,greenland and ,iceland1 and with ,asia where now is ,bering ,strait4 ,these connections were repeatedly made and repeatedly broken during the ,mesozoic and ,cenozoic eras down to the latest epoch1 the ,pleistocene4 ,by comparing the fossil mammals of ,europe with those of ,north ,america for any particular division of geological time1 it is practicable to determine whether the way of intermigration was open or closed1 because separation always led to greater differences between the faunas of the two continents through divergent evolution4 ,correlation with ,south ,america is exceedingly difficult and it is in dealing with this problem that the widest differences of opinion have arisen among geologists4 ,through nearly all the earlier half of the ,tertiary period the two ,americas were separated and1 because of this separation1 their land mammals were utterly different4 ,hence1 the lack of elements common to both continents puts great obstacles in the way of establishing definite time-relations between their geological divisions4 ,only the marine mammals1 whales and dolphins1 were so far alike as to offer some satisfactory basis of comparison4 ,when1 in the later ,tertiary1 a land-connection was established between the two continents1 migrations of mammals from each to the other began1 and thenceforward there were always certain elements common to both1 as there are to-day4 ,in spite of the continuous land between them1 the present faunas of ,north and ,south ,america are very strikingly different1 ,south ,america being1 with the exception of ,australia1 zologically the most peculiar region of the earth4 ,in the following table of the ,south ,american ,cenozoic1 the assignment of the ages to their epochs is largely tentative1 especially as regards the more ancient divisions1 and represents the views generally held by the geologists of ,europe and the ,united ,states2 those of ,south ,america1 on the contrary1 give an earlier date to the ages and stages and refer the older ones to the ,cretaceous instead of the ,tertiary4 ,,cenozoic ,,era 7,south ,america7 ,quaternary period ,recent epoch ,pleistocene epoch--,pampean ,beds1 ,brazilian caverns ,monte ,hermoso age ,pliocene epoch ,catamarca age ,paran age ,tertiary period ,miocene epoch ,santa ,cruz age ,patagonian age ,oligocene epoch ,deseado age 7,pyrotherium ,beds7 ,astraponotus ,beds ,eocene epoch ,casa ,mayor age 7,notostylops ,beds7 ,the ,pleistocene and ,pliocene deposits are most widely distributed over the ,pampas of ,argentina1 but the former occur also in ,ecuador1 ,brazil1 ,chili1 and ,bolivia4 ,the other formations cover extensive areas in ,patagonia1 and some extend into ,tierra del ,fuego4 ,we have next to consider the methods by which past geographical conditions may be ascertained1 a task which1 though beset with difficulties1 is very far from being a hopeless undertaking4 ,as has already been pointed out1 it is perfectly possible for the geologist to determine the circumstances of formation of the various kinds of rocks1 to distinguish terrestrial from aquatic accumulations and1 among the latter1 to identify those which were laid down in the sea and those which were formed in some other body of water4 ,by platting on a map all the marine rocks of a given geological date1 an approximate estimate may be formed as to the extension of the sea over the present land for that particular epoch4 ,it is obvious1 however1 that for those areas which then were land and now are covered by the sea1 no such direct evidence can be obtained1 and only indirect means of ascertaining the former land-connections can be employed4 ,it is in the treatment of this indirect evidence that the greatest differences of opinion arise and1 if two maps of the same continent for the same epoch1 by separate authors1 be compared1 it will be seen that the greatest discrepancies between them are concerning former land-connections and extensions4 ,the only kind of indirect evidence bearing upon ancient land-connections1 now broken by the sea1 that need be considered here is that derived from the study of animals and plants1 both recent and fossil4 ,all-important in this connection is the principle that the same or closely similar species do not arise independently in areas between which there is no connection4 ,it is not impossible that such an independent origin of organisms which the naturalist would class as belonging to the same species may have occasionally taken place1 but1 if so1 it must be the rare exception to the normal process4 ,this principle leads necessarily to the conclusion that the more recently and broadly two land-areas1 now separated by the sea1 have been connected1 the more nearly alike will be their animals and plants4 ,such islands as ,great ,britain1 ,sumatra and ,java must have been connected with the adjacent mainland within a geologically recent period1 while the extreme zological peculiarity of ,australia can be explained only on the assumption that its present isolation is of very long standing4 ,the principle applies to the case of fossils as well as to that of modern animals1 and has already been made use of1 in a preceding section1 in dealing with the ancient land-connections of ,north ,america4 ,it was there shown that the connection of this continent with the ,old ,world and the interruptions of that connection are reflected and recorded in the greater or less degree of likeness in the fossil mammals at any particular epoch4 ,conversely1 the very radical differences between the fossil mammals of the two ,americas imply a long-continued separation of those two continents1 and their junction in the latter half of the ,tertiary period is proved by the appearance of southern groups of mammals in the northern continent1 and of northern groups in ,south ,america4 ,inasmuch as the connection between ,north and ,south ,america still persists1 the geology of the ,isthmus of ,panama should afford testimony in confirmation of the inferences drawn from a study of the mammals4 ,of course1 the separating sea did not necessarily cross the site of the present isthmus2 it might have cut through some part of ,central ,america1 but a glance at the map immediately suggests the isthmus as the place of separation and subsequent connection4 ,as a matter of fact1 isthmian geology is in complete accord with the evidence derived from the mammals4 ,even near the summit of the hills which form the watershed between the ,atlantic and the ,pacific and through which the great ,culebra ,cut passes1 are beds of marine ,tertiary shells1 showing that at that time the land was completely submerged4 ,this does not at all preclude the possibility of other transverse seas at the same period2 indeed1 much of ,central ,america was probably under the sea also1 but the geology of that region is still too imperfectly known to permit positive statements4 ,when several different kinds of testimony1 each independent of the other1 can be secured and all are found to be in harmony1 the strength of the conclusion is thereby greatly increased4 ,many distinct lines of evidence support the inference that ,north and ,south ,america were completely severed for a great part of the ,tertiary period4 ,this is indicated in the clearest manner1 not only by the geological structure of the ,isthmus and by the mammals1 living and extinct1 as already described1 but also by the fresh-water fishes1 the land-shells1 the reptiles and many other groups of animals and plants4 ,the distribution of marine fossils may render the same sort of service in elucidating the history of the sea as land-mammals do for the continents1 demonstrating the opening and closing of connections between land-areas and between oceans4 ,the sea1 it is true1 is one and undivided1 the continental masses being great islands in it1 but1 nevertheless1 the sea is divisible into zological provinces1 just as is the land4 ,temperature1 depth of water1 character of the bottom1 etc41 are factors that limit the range of marine organisms1 as climate and physical barriers circumscribe the spread of terrestrial animals4 ,professor ,perrin ,smith has shown that in the ,mesozoic era ,bering ,strait was repeatedly opened and closed1 and that each opening and closing was indicated by the geographical relationships of the successive assemblages of marine animals that are found in the ,mesozoic rocks of ,california and ,nevada4 ,when the ,strait was open1 the coast-line between ,north ,america and ,asia was interrupted and the ,north ,pacific was cooled by the influx of water from the ,arctic ,sea4 ,at such times1 sea-animals from the ,russian and ,siberian coasts extended their range along the ,american side as far south as ,mexico1 and no forms from the eastern and southern shores of ,asia accompanied them4 ,on the other hand1 when the ,strait was closed1 the ,arctic forms were shut out and the continuous coast-line and warmer water enabled the ,japanese1 ,indian1 and even ,mediterranean animals to extend their range to the ,pacific coast of ,north ,america4 ,a comparison of the marine fishes of the two sides of the ,isthmus of ,panama shows an amount and degree of difference between the two series as might be expected from the length of time that they have been separated by the upheaval of the land4 ,in working out the geographical conditions for any particular epoch of the earth's history1 it is possible to go much farther than merely gaining an approximate estimate of the distribution of land and sea2 many other important facts may be gathered from a minute examination of the rocks in combination with a genetic study of topographical forms4 ,by this physiographical method1 as it is called1 the history of several of the great mountain-ranges has been elaborated in great detail4 ,it is quite practicable to give a geological date for the initial upheaval and to determine whether one or many such series of movements have been involved in bringing about the present state of things4 ,similarly1 the history of plains and plateaus1 hills and valleys1 lake and river systems1 may be ascertained1 and for the earth's later ages1 at least1 a great deal may be learned regarding the successive forms of the land-surfaces in the various continents4 ,it would be very desirable to explain the methods by which these results are reached1 but this could hardly be done without writing a treatise on physiography1 for which there is no room in this chapter4 ,we must be permitted to make use of the results of that science without being called upon to prove their accuracy4 ,no factor has a more profound effect in determining the character and distribution of living things than climate1 of which the most important elements1 for our purpose1 are temperature and moisture4 ,one of the most surprising results of geological study is the clear proof that almost all parts of the earth have been subjected to great vicissitudes of climate1 and a brief account of the evidence which has led to this unlooked for result will not be out of place here4 ,the evidence of climatic changes is of two principal kinds1 7#a7 that derived from a study of the rocks themselves1 and 7#b7 that given by the fossils of the various epochs4 ,so far as the rocks laid down in the sea are concerned1 little has yet been ascertained regarding the climatic conditions of their formation1 but the strata which were deposited on the land1 or in some body of water other than the sea1 often give the most positive and significant information concerning the circumstances of climate which prevailed at the time of their formation4 ,certain deposits1 such as gypsum and rock-salt1 are accumulated only in salt lakes1 which1 in turn1 are demonstrative proof of an arid climate4 ,a salt lake could not exist in a region of normal rainfall and1 from the geographical distribution of such salt-lake deposits1 it may be shown that arid conditions have prevailed in each of the continents and1 not only once1 but many times4 ,as a rule1 such aridity of climate was relatively local in extent1 but sometimes it covered vast areas4 ,for example1 in the ,permian1 the last of the ,palozoic1 and the ,triassic1 the first of the ,mesozoic periods 7see ,table1 p4 #ae7 nearly all the land-areas of the northern hemisphere were affected1 either simultaneously or in rapid succession4 ,until a comparatively short time ago1 it was very generally believed that the ,glacial or ,pleistocene epoch1 which was so remarkable and conspicuous a feature of the ,quaternary period1 was an isolated phenomenon1 unique in the entire history of the earth4 ,now1 however1 it has been conclusively shown that such epochs of cold have been recurrent and that no less than five of these have left unmistakable records in as many widely separated periods of time4 ,when the hypothesis of a great 8,ice ,age0 in the ,pleistocene was first propounded by the elder ,agassiz1 it was naturally received with general incredulity1 but the gradual accumulation of proofs has resulted in such an overwhelming weight of testimony1 that the glacial hypothesis is now accepted as one of the commonplaces of ,geology4 ,the proofs consist chiefly in the characteristic glacial accumulations1 moraines and drift-sheets1 which cover such enormous areas in ,europe and ,north ,america and1 on a much smaller scale1 in ,patagonia1 and in the equally characteristic marks of glacial wear left upon the rocks over which the ice-sheets moved4 ,many years later it was proved that the ,permian period had been a time of gigantic glaciation1 chiefly in the southern hemisphere1 when vast ice-caps moved slowly over parts of ,south ,america1 ,south ,africa1 ,australia and even of ,india4 ,the evidence is of precisely the same nature as in the case of the ,pleistocene glaciation4 ,in not less than three more ancient periods1 the ,devonian1 ,cambrian1 and ,algonkian1 proofs of glacial action have been obtained4 ,while the rocks themselves thus afford valuable testimony as to the climatic conditions which prevailed at the time and place of their formation1 this testimony is fragmentary1 missing for very long periods1 and must be supplemented from the information presented by the fossils4 ,as in all matters where fossils are involved1 the evidence must be cautiously used1 for hasty inferences have often led to contradictory and absurd conclusions4 ,when properly employed1 the fossils give a more continuous and complete history of climatic changes than can1 in the present state of knowledge1 be drawn from a study of the rocks alone4 ,for this purpose plants are particularly useful1 because the great groups of the vegetable kingdom are more definitely restricted in their range by the conditions of temperature and moisture than are most of the correspondingly large groups of animals4 ,not that fossil animals are of no service in this connection2 quite the contrary is true1 but the evidence from them must be treated more carefully and critically4 ,to illustrate the use of fossils as recording climatic changes in the past1 one or two examples may be given4 ,in the ,cretaceous period a mild and genial climate prevailed over all that portion of the earth whose history we know1 and was1 no doubt1 equally the case in the areas whose geology remains to be determined4 ,the same conditions extended far into the ,arctic regions1 and abundant remains of a warm-temperate vegetation have been found in ,greenland1 ,alaska and other ,arctic lands4 ,where now only scanty and minute dwarf willows and birches can exist1 was then a luxuriant forest growth comprising almost all of the familiar trees of our own latitudes1 a most decisive proof that in the ,cretaceous the climate of the ,arctic regions must have been much warmer than at present and that there can have been no great accumulation of ice in the ,polar seas4 ,conditions of similar mildness obtained through the earlier part of the ,tertiary4 ,in the ,eocene epoch large palm-trees were growing in ,wyoming and ,idaho1 while great crocodiles and other warm-country reptiles abounded in the waters of the same region4 ,it is of particular interest to inquire how far the fossils of ,glacial times confirm the inferences as to a great climatic change which are derived from a study of the rocks1 for this may be taken as a test-case4 ,any marked discrepancy between the two would necessarily cast grave doubt upon the value of the testimony of fossils as to climatic conditions4 ,the problem is one of great complexity1 for the ,pleistocene was not one long epoch of unbroken cold1 but was made up of ,glacial and ,interglacial ages1 alternations of colder and milder conditions1 and some1 at least1 of the ,interglacial ages had a climate warmer than that of modern times4 ,such great changes of temperature led to repeated migrations of the mammals1 which were driven southward before the advancing ice-sheets and returned again when the glaciers withdrew under the influence of ameliorating climates4 ,any adequate discussion of these complex conditions is quite out of the question in this place and the facts must be stated in simplified form1 as dealing only with the times of lowered temperature and encroaching glaciers4 ,the plants largely fail us here1 for little is known of ,glacial vegetation1 but1 on the other hand1 a great abundance of the fossil remains of animal life of that date has been collected1 and its testimony is quite in harmony with that afforded by the ice-markings and the ice-made deposits4 ,arctic shells in the marine deposits of ,england1 the valley of the ,ottawa ,river and of ,lake ,champlain1 ,walruses on the coast of ,new ,jersey1 ,reindeer in the south of ,france1 and ,caribou in southern ,new ,england1 ,musk-oxen in ,kentucky and ,arkansas1 are only a few examples of the copious evidence that the climate of the regions named in ,glacial times was far colder than it is to-day4 ,i have thus endeavored to sketch1 necessarily in very meagre outlines1 the nature of the methods employed to reconstruct the past history of the various continents and the character of the evidence upon which we must depend4 ,should the reader be unconvinced and remain sceptical as to the possibility of any such reconstruction1 he must be referred to the numerous manuals of ,geology1 in which these methods are set forth with a fulness which cannot be imitated within the limits of a single chapter4 ,the methods are sound1 consisting as they do merely in the application of 8systematized common sense0 7in ,huxley's phrase7 to observed facts1 but by no means all applications of them are to be trusted4 ,not to mention ill-considered and uncritical work1 or inverted pyramids of hypothesis balanced upon a tiny point of fact1 it should be borne in mind that such a complicated and difficult problem as the reconstruction of past conditions can be solved only by successive approximations to the truth1 each one partial and incomplete1 but less so than the one which preceded it4 ,,chapter ,,ii ,,methods ,,of ,,investigation--,,pal,,ontological ,palontology is the science of ancient life1 animal and vegetable1 the ,zology and ,botany of the past1 and deals with fossils4 ,fossils are the recognizable remains or traces of animals or plants1 which were buried in the rocks at the time of the formation of those rocks4 ,in a geological sense1 the term rock includes loose and uncompacted materials1 such as sand and gravel1 as well as solid stone4 ,granting the possibility of so determining the relative dates of formation of the rocks1 that the order of succession of the fossils in time may be ascertained in general terms1 the question remains3 ,what use1 other than geological1 can be made of the fossils8 ,in dealing with this question1 attention will be directed almost exclusively to the mammals1 the group with which this book is concerned4 ,as a preliminary to the discussion1 something should be said of the ways in which mammals became entombed in the rocks in which we find them4 ,in this connection it should be remembered that1 however firm and solid those rocks may be now1 they were originally layers of loose and uncompacted material1 deposited by wind or water1 and that each layer formed in its turn the surface of the earth1 until buried by fresh accumulations upon it1 it may be to enormous depths4 ,one method of the entombing of land-mammals1 which has frequently been of great importance1 is burial in volcanic dust and so-called ash1 which has been compacted into firm rock4 ,during a great volcanic eruption enormous quantities of such finely divided material are ejected from the crater and are spread out over the surrounding country1 it may be for distances of hundreds of miles4 ,thus will be buried the scattered bones1 skeletons1 carcasses1 that happen to be lying on the surface2 and if the fine fragments are falling rapidly1 many animals will be buried alive and their skeletons preserved intact4 ,a modern instance of this is given by the numerous skeletons of men and domestic animals buried in the volcanic ash which overwhelmed ,pompeii in #gi ,a4,d4 ,pliny the ,younger1 who witnessed that first recorded eruption of ,vesuvius1 tells us in a letter written to ,tacitus1 that far away at ,misenum1 west of ,naples1 it was often necessary to rise and shake off the falling ashes1 for fear of being buried in them4 ,in the ,santa ,cruz formation of ,patagonia 7see p4 #abd71 which has yielded such a wonderful number and variety of well-preserved fossils1 the bones are all found in volcanic dust and ash compacted into a rock1 which is usually quite soft1 but may become locally very hard4 ,the ,bridger formation of ,wyoming 7p4 #aaj7 and the ,john ,day of eastern ,oregon 7p4 #aaf7 are principally made up of volcanic deposits2 and no doubt there are several others among the ,tertiary stages which were formed in the same way1 but have not yet received the microscopic study necessary to determine this4 ,much information concerning the mammalian life of the ,pleistocene1 more especially in ,europe and in ,brazil 7p4 #baa71 has been derived from the exploration of caverns4 ,some of these caves were the dens of carnivorous beasts and contain multitudes of the bones of their victims1 as well as those of the destroyers themselves4 ,others1 such as the ,port ,kennedy ,cave1 on the ,schuylkill ,river above ,philadelphia1 the ,frankstown ,cave in central ,pennsylvania1 the ,conard ,fissure in ,arkansas1 are hardly caverns in the ordinary sense of the word1 but rather narrow fissures1 into which bones and carcasses were washed by floods1 or living animals fell from above and died without being able to escape4 ,the bones are mostly buried in the earth which partially or completely fills many caverns and may be covered by a layer of stalagmite1 derived from the solution and re-deposition of the limestone of the cavern-walls1 by the agency of percolating waters4 ,a mode of preservation which is unfortunately rare is exemplified by the asphaltic deposits near ,los ,angeles1 at ,rancho ,la ,brea1 which have been very fully described by ,professor ,j4 ,c4 ,merriam of the ,university of ,california4 ,the asphalt has been formed by the oxidation and solidification of petroleum1 which has risen up through the ,pleistocene rocks from the oil-bearing shales below4 ,at one stage in the conversion of petroleum into asphalt1 tar-pools of extremely viscid and adhesive character were1 and still are1 formed on the surface of the ground2 and these pools were veritable traps for mammals and birds and for the beasts and birds of prey which came to devour the struggling victims4 8,the manner in which tar or asphalt pools may catch unsuspecting animals of all kinds is abundantly illustrated at the present time in many places in ,california1 but nowhere more strikingly than at ,rancho ,la ,brea itself1 where animals of many kinds have frequently been so firmly entrapped that they died before being discovered1 or if found alive were extricated only with the greatest difficulty4 ,as seen at this locality1 the tar issuing from springs or seepages is an exceedingly sticky1 tenacious substance which is removed only with the greatest difficulty from the body of any animal with which it may come in contact4 ,small mammals1 birds1 or insects running into the soft tar are very quickly rendered helpless by the gummy mass1 which binds their feet1 and in their struggles soon reaches every part of the body4 ,around the borders of the pools the tar slowly hardens by the evaporation of the lighter constituents until it becomes as solid as an asphalt pavement4 ,between the hard and soft portions of the mass there is a very indefinite boundary1 the location of which can often be determined only by experiment1 and large mammals in many cases run into very tenacious material in this intermediate zone1 from which they are unable to extricate themselves40 ,the foregoing account refers to what may actually be observed at the present time2 in regard to the ,pleistocene1 ,professor ,merriam says3 8,in the natural accumulation of remains at the tar pools through accidental entangling of animals of all kinds1 it is to be presumed that a relatively large percentage of the individuals entombed would consist of young animals with insufficient experience to keep them away from the most dangerous places1 or with insufficient strength to extricate themselves4 ,there would also be a relatively large percentage of old1 diseased1 or maimed individuals that lacked strength to escape when once entangled4 ,in the census of remains that have been obtained up to the present time the percentages of quite young1 diseased1 maimed1 and very old individuals are certainly exceptionally large4444 ,in addition to the natural accumulation of animal remains through the entangling of creatures of all kinds by accidental encountering of the tar1 it is apparent from a study of the collections obtained that some extraordinary influence must have brought carnivorous animals of all kinds into contact with the asphalt with relatively greater frequency than other kinds of animals4 ,in all the collections that have been examined the number of carnivorous mammals and birds represented is much greater than that of the other groups4444 ,whenever an animal of any kind is caught in the tar1 its struggles and cries naturally attract the attention of carnivorous mammals and birds in the immediate vicinity1 and the trapped creature acts as a most efficient lure to bring these predaceous animals into the soft tar with it4 ,it is not improbable that a single small bird or mammal struggling in the tar might be the means of entrapping several carnivores1 which in turn would naturally serve to attract still others4444 ,in the first excavations carried on by the ,university of ,california a bed of bones was encountered in which the number of saber-tooth and wolf skulls together averaged twenty per cubic yard40#a ,as the animals were thus entombed alive1 it would be expected that a large number of complete skeletons would be preserved1 but this is not the case3 8connected skeletons are not common40 ,this scattering and mingling of the bones were due partly to the trampling of the heavier animals in their struggles to escape1 but1 in more important degree1 to the movements within the tar and asphalt4 ,in arid and semi-arid regions great quantities of sand and dust are transported by the wind and deposited where the winds fail1 or where vegetation entangles and holds the dust4 ,any bones1 skeletons or carcasses which are lying on the surface will thus be buried1 and even living animals may be suffocated and buried by the clouds of dust4 ,an example of such wind-made accumulations is the ,sheridan formation 7,equus ,beds1 see p4 #aca71 which covers vast areas of the ,great ,plains from ,nebraska to ,mexico and contains innumerable bones1 especially of horses4 ,in this formation in northwestern ,kansas1 ,professor ,williston found nine skeletons of the large peccary 7,platygonus leptorhinus71 lying huddled together1 with their heads all pointing in the same direction1 and in the upper ,miocene 7p4 #aba7 of ,south ,dakota ,mr4 ,gidley discovered six skeletons of three-toed horses 7,neohipparion whitneyi7 crowded together1 killed and buried probably by a sandstorm4 ,similar illustrations might be gathered from many other parts of the world4 ,swamps and bogs may1 especially under certain conditions1 become the burial places of great numbers of animals1 which venture into them1 become buried and are unable to extricate themselves4 ,especially is this true in times of great drought1 when animals are not only crazed with thirst1 but very much weakened as well1 and so unable to climb out of the clinging mud4 ,in an oft-quoted passage1 ,darwin gives a vivid description of the effects of a long drought in ,argentina between the years #ahbg and #ahcj4 8,during this time so little rain fell1 that the vegetation1 even to the thistles1 failed2 the brooks were dried up1 and the whole country assumed the appearance of a dusty high road40 8,i was informed by an eyewitness that the cattle in herds of thousands rushed into the ,paran1 and being exhausted by hunger they were unable to crawl up the muddy banks1 and thus were drowned4 ,the arm of the river which runs by ,san ,pedro was so full of putrid carcasses1 that the master of a vessel told me that the smell rendered it quite impassable4 ,without doubt several hundred thousand animals thus perished in the river2 their bodies when putrid were seen floating down the stream2 and many in all probability were deposited in the estuary of the ,plata4 ,all the small rivers became highly saline1 and this caused the death of vast numbers in particular spots2 for when an animal drinks of such water it does not recover4 ,azara describes the fury of the wild horses on a similar occasion1 rushing into the marshes1 those which arrived first being overwhelmed and crushed by those which followed4 ,he adds that more than once he has seen the carcasses of upwards of a thousand wild horses thus destroyed4444 ,subsequently to the drought of #ahbg to #ahcb1 a very rainy season followed1 which caused great floods4 ,hence it is almost certain that some thousands of the skeletons were buried by the deposits of the very next year40#b ,in the arid and desolate regions of the interior of ,south ,australia is a series of immense dry lakes1 which only occasionally contain water and ordinarily 8are shallow1 mud-bottomed or salt-encrusted claypans only40 ,one of these1 ,lake ,callabonna1 is of great interest as having preserved in its soft mud many remains of ancient life1 of creatures which were mired in the clay and destroyed1 as has been described by ,dr4 ,e4 ,c4 ,stirling4 8,there is1 however1 compensation for the unpromising physical features of ,lake ,callabonna in the fact that its bed proves to be a veritable necropolis of gigantic extinct marsupials and birds which have apparently died where they lie1 literally1 in hundreds4 ,the facts that the bones of individuals are often unbroken1 close together1 and1 frequently1 in their proper relative positions1 the attitude of many of the bodies and the character of the matrix in which they are embedded1 negative any theory that they have been carried thither by floods4 ,the probability is1 rather1 that they met their deaths by being entombed in the effort to reach food or water1 just as even now happens in dry seasons1 to hundreds of cattle which1 exhausted by thirst and starvation1 are unable to extricate themselves from the boggy places that they have entered in pursuit either of water or of the little green herbage due to its presence4 ,the accumulation of so many bodies in one locality points to the fact of their assemblage around one of the last remaining oases in the region of desiccation which succeeded an antecedent condition of plenteous rains and abundant waters40 ,it is a very general experience in collecting fossil mammals to find that they are not evenly or uniformly distributed through the beds1 but rather occur in 8pockets10 where great numbers of individuals are crowded together1 while between the 8pockets0 are long stretches of barren ground4 ,it is equally common to find the bones thickly distributed in certain layers1 or beds1 and the layers above and below entirely wanting in fossils4 ,the reasons for this mode of occurrence have been partially explained in the foregoing paragraphs1 but the reason differs for each particular mode of entombment4 ,the important part played by drought in causing such accumulation of closely crowded bodies in swamps and mud-holes is indicated in the quotations from ,darwin and ,stirling2 but similar accumulations may take place on hard ground1 as was observed in central ,africa by ,gregory4 8,here and there around a water hole we found acres of ground white with the bones of rhinoceroses and zebra1 gazelle and antelope1 jackal and hyena4444 ,these animals had crowded around the dwindling pools and fought for the last drops of water40#c ,even in normal seasons springs and water holes and the drinking places in streams are the lurking places of beasts of prey and crocodiles1 so that great accumulations of bones are made around these spots4 ,a succession of unusually severe winters frequently leads to great mortality among mammals1 as happened in ,patagonia in the winter of #ahii1 when enormous numbers of ,guanaco perished of starvation on the shore of ,lake ,argentine1 where they came to drink4 ,bones which are exposed on the surface of the ground decay and crumble to pieces in the course of a very few years2 and if they are to be preserved as fossils1 it is necessary that they should be buried under sedimentary or volcanic deposits4 ,several such modes of burial have been described in the foregoing paragraphs1 but there are other and equally important methods1 which remain to be considered4 ,the deposits made by rivers are often extremely rich in fossils1 and most of the ,tertiary formations of the ,great ,plains are now ascribed to the agency of rivers4 ,the flood-plain of a stream1 or that part of its basin which is periodically overflowed1 is gradually built up by the layers of clay and silt thrown down by the relatively still waters of the flooded area1 and scattered bones1 skeletons or carcasses that may have been lying on the ground before the freshet are buried in the deposits4 ,bones covered up in this manner frequently show the marks of teeth of rodents or carnivores which have gnawed them when lying exposed4 ,deposits made in the stream-channels1 where the current was swiftest1 are of coarser materials such as gravel and sand1 and these often contain the skeletons of animals which were drowned and swept downward by the flooded stream4 ,when the ,bison 7the mistakenly so-called ,buffalo7 still roamed in countless herds over the western plains1 immense numbers of them were drowned in the upper ,missouri ,river by breaking through the ice1 when they attempted to cross at times when the ice had not attained its winter thickness1 or was weakened by melting in the spring4 ,no doubt1 the bed of that river contains innumerable bones of the ,bison4 ,frequently1 too1 animals are caught in quicksands and1 unable to escape1 are buried in the soft mass2 fossil skeletons which are preserved in sandstones in an erect or standing position are usually to be interpreted in this manner4 ,the sedimentary accumulations formed in lakes and ponds sometimes yield fossil bones or skeletons in considerable numbers1 which have1 for the most part1 been derived from the carcasses of animals carried into the lake by streams4 ,a newly drowned mammal sinks to the bottom and1 if sufficient sediment be quickly deposited upon it1 it may be anchored there and fossilized as a complete skeleton4 ,otherwise1 when distended by the gases of putrefaction1 the body will rise and float on the surface1 where it will be attacked and pulled about by crocodiles1 fishes and other predaceous creatures4 ,as the bones are loosened in the course of decomposition1 they will drop to the bottom and be scattered1 now here1 now there1 over a wide area4 ,land mammals are rarely found in marine rocks1 or such deposits as were made on the sea-bottom2 but the remains of marine mammals1 whales1 porpoises1 dolphins1 seals1 etc4 are often found in large numbers4 ,in principle1 the method of entombment is the same as in the case of lakes1 but currents may drift to some bay or cove multitudes of carcasses of these marine mammals4 ,at ,antwerp1 in ,belgium1 incredible quantities of such remains have been exposed in excavations and in all probability were drifted by currents into a quiet and shallow bay1 which was subsequently converted into land4 ,while the foregoing account by no means exhausts the various methods of accumulation and burial of the skeletons and scattered bones of mammals1 it covers the more important of these methods sufficiently for a general understanding of the different processes4 ,in whatever manner the preservation may have been effected1 there is great difference in the relative abundance and completeness among the fossils of the various kinds of mammals which were living at the same time and in the same area4 ,it need hardly be said1 that the more abundant any species was1 the better was the chance of its being represented among the fossils2 hence1 gregarious species1 living in large herds1 were more likely to be preserved than those which led a solitary existence1 or were individually rare4 ,most of the hoofed mammals are and apparently always have been gregarious1 and are therefore much better represented among the fossils1 and are1 in consequence1 better known than the beasts of prey1 which1 of necessity1 were individually less numerous and generally solitary in habits4 ,not only this1 but large and medium-sized mammals1 with strong and heavy bones1 were better fitted to withstand the accidents of entombment and subsequent preservation than small creatures with delicate and fragile skeletons4 ,the mere dead weight of over-lying sediments often crushes and distorts the bones1 and the movements of uplift1 compression1 folding and fracture1 to which so many strata have been subjected1 did still further damage to the fossils4 ,the percolating waters1 which for ages have traversed the porous rocks1 often attack and dissolve the bones1 completely destroying the minute ones and greatly injuring those which are massive and strong4 ,in consequence of all those accidents it frequently happens that only the teeth1 the hardest and most resistant of animal structures1 and it may be the dense and solid jaw-bones1 are all that remain to testify of the former existence of some creature that long ago vanished from the earth4 ,very many fossil mammals are known exclusively from the teeth1 and it is this fact which makes the exact study of teeth so peculiarly important to the palontologist4 ,in view of all these facts1 it is not surprising that concerning the history of many mammalian groups we have but scanty information1 or none at all1 while in the case of others the story is wonderfully full and detailed4 ,the latter are1 very generally1 the groups which were not only numerically abundant at all stages of their history1 but also had skeletons that were strong enough to resist destruction2 while the groups as to which there is little or no information are chiefly of small and fragile animals1 or such as were always rare4 ,for example1 a great deal has been learned regarding the development of horses and rhinoceroses in ,north ,america1 but the history of the tapirs is very unsatisfactorily known1 because1 while horses and rhinoceroses were common1 tapirs were solitary and rare4 ,in ,europe bats have been found in the ,eocene1 ,oligocene and ,miocene1 and there is no reason to suppose that they were not equally ancient and equally abundant in ,america2 but none have been found in the western hemisphere in any formation older than the ,pleistocene4 ,all things considered1 the extraordinary fact is1 not that so many forms have irretrievably perished1 but that so much has been preserved1 escaping all the chances of destruction4 ,as to the degree of preservation in fossil mammals1 we have to do almost entirely with bones and teeth4 ,with very rare exceptions1 and those all of late geological date1 the viscera1 muscles1 skin1 hair1 horns1 hoofs and claws have been completely destroyed and have vanished without leaving a trace4 ,in northern ,siberia the gravel soil is permanently frozen to a depth of several hundred feet and contains the intact carcasses of elephants and rhinoceroses of ,pleistocene date and notably different from any species of these animals now in existence4 ,sometimes such a carcass is disinterred from a bluff by the cutting action of a stream and is in a state of nearly complete preservation1 with hide1 hair and flesh almost as in an animal freshly killed4 ,from these remains it has been learned that the ,mammoth was an elephant densely covered with hair and wool1 just as he was depicted in the carvings and cave-paintings of ,pleistocene ,man in ,europe1 where ,mammoth bones have been abundantly found1 and also that there were ,siberian rhinoceroses similarly protected against the cold4 ,mammoth remains with hide and flesh1 but much less complete1 have likewise been found in ,alaska4 ,in a cavern in southern ,patagonia an expedition from the ,la ,plata ,museum discovered1 with the remains of a gigantic1 extinct ground-sloth1 large pieces of the skin still covered with hair and affording most welcome information as to the colouration of these most curious animals4 ,the skin had been preserved from decay by deep burial in dry dust4 ,mummies of ,pleistocene rodents have been found in the dry caves of ,portugal1 whereas in the ordinary caves which are damp or wet1 only bones are preserved4 ,unfortunately1 as has been said1 such instances of complete preservation are very rare1 and none are known of mammals more ancient than those of the ,pleistocene epoch4 ,in general1 it may be said that the higher the geological antiquity of a skeleton is1 the greater is the chemical alteration which it has undergone4 ,bones of ,pleistocene or later date have1 as a rule1 suffered little change beyond the loss of more or less of their animal matter1 the amount of such loss depending chiefly upon exposure to the air4 ,bones which1 for thousands or tens of thousands of years1 have been buried in dense cave-earth1 in an antiseptic peat-bog1 or in asphalt1 are often perfectly sound and fresh when taken up4 ,skeletons of the antecedent 7,tertiary7 period are1 on the other hand1 very frequently petrified2 that is to say1 the original substance of the bones has been completely removed and replaced by some stony material1 most commonly lime or flint4 ,this substitution took place very gradually1 molecule by molecule1 so that not only is the form of the bone or tooth most accurately reproduced1 but the internal1 microscopic structure is perfectly retained and may be studied to as great advantage as in the case of modern animals4 ,while1 save in the rarest instances1 only the hard parts of fossil mammals remain to testify of their structure1 very important information as to the size1 form and external character of the brain may be secured from 8brain-casts10 which may be natural or artificial4 ,the pressure of the mud1 sand or other material1 in which the fossil was embedded1 filled up all openings in the skeleton and1 as the brain decayed and disappeared1 its place was taken by this material1 which subsequently hardened and solidified and quite accurately reproduces the external form and character of the brain4 ,when a fossil skull is exposed and shattered by weathering1 the natural brain-cast often remains intact1 and a great many such specimens are in the collections4 ,an artificial cast is made by sawing open the cranial cavity1 cleaning out the stony matrix which fills it and then pouring liquid gelatine or plaster of ,paris into the cavity4 ,these artificial casts are often quite as satisfactory as the natural ones4 ,as has been shown above1 the history of the mammals is recorded1 save in a very few instances1 in terms of bones and teeth and1 to the uninitiated1 it might well seem that little could be accomplished with such materials4 ,however1 it is the task1 and the perfectly feasible task1 of palontology to make these dry bones live4 ,it is a current and exceedingly mischievous notion that the palontologist can reconstruct a vanished animal from a single bone or tooth and1 in spite of repeated slayings1 this delusion still flourishes and meets one in modern literature at every turn4 ,no doubt1 much of the scepticism with which attempts to restore extinct animals are met by many intelligent people is traceable to the widespread belief that such off-hand and easy-going methods are used in the work4 ,so far from being able to make a trustworthy reconstruction from a few scattered bones1 competent palontologists have been sometimes led completely astray in associating the separated parts of the same skeleton4 ,more than once it has happened that the dissociated skull and feet of one and the same animal have been assigned to entirely different groups1 just because no one could have ventured1 in advance of experience1 to suppose that such a skull and teeth could belong to a creature with such feet4 ,in all these cases 7and they are few7 the error has been finally corrected by the discovery of the skeleton with all its essential parts in their natural connection4 ,while the number of complete skeletons of ,tertiary mammals as yet collected is comparatively small1 it is often possible to construct a nearly complete specimen from several imperfect ones1 all of which can be positively shown to belong to the same species4 ,such composite skeletons are almost as useful as those in which all the parts pertain to a single individual1 though in making the drawings it is not easy to avoid slight errors of proportion4 ,it must not be supposed that no successful restoration of missing bones is practicable2 on the contrary1 this can often be done very easily1 but only when all the essential parts of the skeleton are known4 ,even if an unlimited number of perfect skeletons were available1 of what use would they be8 ,a skeleton is a very different looking object from a living animal1 and how is it possible to infer the latter from the former8 ,do the many restorations of extinct mammals which this book owes to the skill of ,mr4 ,horsfall and ,mr4 ,knight deserve any other consideration than that due to pleasing1 graceful or grotesque fancies1 with no foundation of solid fact8 ,to answer these questions1 it is necessary first to consider the relations of the bony structure to the entire organism and then to discuss the principles in accordance with which the restorations have been made4 ,the skeleton is far from being merely the mechanical frame-work of the animal4 ,such a frame-work it is1 of course1 but it is much more than that2 it is the living and growing expression of the entire organism and is modified1 not only by age1 but by the conditions of the environment and accidental circumstances as well4 ,the bones of the same individual differ very materially in early youth1 maturity and old age2 so long as the animal lives1 its bones are perpetually changing1 slowly it is true1 but with ready response to needs4 ,not only that1 but dislocated bones may and frequently do develop entirely new joints1 and their internal structure is remodelled to meet the requirements of stresses differing in character or direction from those of normal1 uninjured bones4 ,the general form and proportions of any mammal are determined chiefly by its muscular system and this may be directly and confidently inferred from its skeleton1 for the muscles which are of importance in this connection are attached to the bones and leave their indelible and unmistakable mark upon them4 ,in any good text-book of anatomy this extremely intimate relation of bone and muscle is made clear2 and it is shown how each attachment of muscle1 tendon and ligament is plainly indicated by rough lines1 ridges1 projections or depressions1 which speak a language intelligible enough to those who have learned to interpret it4 ,given the skeleton1 it is no very difficult task to reconstruct the muscular system in sufficient detail4 ,further1 the teeth afford valuable information as to the food1 habits and appearance of the animal1 for the bulk of the viscera1 a significant element in the general form1 is principally conditioned by the character of the diet4 ,beasts of prey1 which live by catching and devouring other animals1 have a certain likeness to one another1 even though they are in no wise related1 except as all mammals are4 ,the ,thylacine1 or so-called 8,tasmanian ,wolf0 7,thylacynus cynocephalus71 a marsupial and related to the opossums1 is deceptively like the true wolves in appearance1 although belonging to an order 7,marsupialia7 almost as widely separated from that to which the wolves belong 7,carnivora7 as two mammalian groups well can be4 ,this resemblance is as clearly indicated by the skeletons as by the living animals themselves1 though the fundamental differences of structure which distinguish the marsupial from the carnivore are no less clearly displayed4 ,large herbivorous mammals too1 though referable to very different orders1 bear a strong resemblance to one another1 the characteristic differences1 so far as the living animal is concerned1 appearing chiefly in the head4 ,it was this general likeness that induced ,cuvier to form his order1 8,pachydermata10 which comprised elephants1 rhinoceroses1 hippopotamuses1 tapirs1 etc41 animals that are now distributed into no less than three separate orders2 aside from the head1 all of these forms are quite distinctly similar in appearance4 ,of course1 the external features1 such as ears1 tail1 skin and hair1 are most important factors in the general make-up of any mammal2 and1 as to these matters1 the fossils leave us largely in the lurch1 save in the all too rare cases1 like the ,siberian ,mammoth1 in which these external features are actually preserved4 ,two artists may so restore the same animal as to result in two very different pictures1 and no one can positively decide between them2 just as two modern mammals1 which are closely related and have very similar skeletons1 may yet differ markedly in outward appearance1 because of the different character of the skin1 as do1 for example1 the ,bornean and ,indian rhinoceroses4 ,yet even in dealing with purely external features1 we are not left altogether to conjecture4 ,ears of unusual size or form frequently leave some indication of this on the skull1 and the presence or absence of a proboscis can nearly always be inferred with confidence from the character of the bones of the nose and muzzle4 ,the length and thickness of the tail may be generally directly deduced from the caudal vertebr1 but whether it was close-haired and cylindrical1 or bushy1 or tufted at the end1 or flat and trowel-shaped1 as in the ,beaver1 is not determinable from the bones alone4 ,illustration3 ,,fig4 #d4--,wild sow and pigs1 showing the uniform colour of the adult and stripes of the young4 ,most uncertain of all the characters which determine outward appearance are the hair and the pattern of colouration2 the ,horse and ,zebra differ much more decidedly in the living form than their skeletons would lead one to expect1 as do also the ,lion1 the ,tiger and the ,leopard4 ,the curious and exceptional colour-pattern of the ,okapi1 that remarkable giraffe-like animal but lately discovered in the equatorial forests of western ,africa1 could never have been inferred from a study of the skeleton alone4 ,however1 even in the problem of colour-patterns there is more to go upon than sheer guess-work1 for certain definite principles of animal colouration have been ascertained2 the great difficulty lies in the application of these principles to a particular case4 ,it is quite certain that the naked1 hairless skin is never primitive1 but always a comparatively late acquisition and1 in many mammalian orders1 is not found at all4 ,aside from a few domesticated animals1 this type of skin occurs only in very large herbivorous mammals living in warm climates1 such as elephants1 rhinoceroses and hippopotamuses1 in a few burrowers1 and in marine mammals1 like the walruses1 whales1 porpoises1 etc4 ,useful hints as to the colouring of ancient and extinct forms may be gathered from a study of series of living animals1 such as lizards and butterflies1 in which the development of a definite scheme of colouration may be followed step by step4 ,young animals very frequently retain more or less distinct traces of the ancestral colouration1 which disappear in the adult1 for the development of the individual is1 in some respects at least1 an abbreviated and condensed recapitulation of the history of the species4 ,in many mammals which1 in the adult condition1 have a solid body-colour1 the young are striped or spotted1 a strong indication that these mammals were derived from striped or spotted ancestors4 ,thus1 the ,wild ,boar has a uniform body-colour in the full-grown stage1 but the pigs are longitudinally striped2 many deer are spotted throughout life1 as in the ,fallow ,deer1 the ,axis ,deer of ,india and others1 but the great majority of the species1 including all the ,american forms1 have uniform colouration1 while the fawns are always spotted4 ,lion cubs are also spotted and the adults have a uniform tawny colour1 and many such examples might be given4 ,illustration3 ,,fig4 #e4--;,fawns of the ,mule ,deer 7,odocoileus hemionus74 ,compare with ,fig4 #hc1 p4 #afg4 7,by permission of the ,n4 ,y4 ,zolog4 ,society47 ,the study of colouration among existing animals has led to the conclusion that in mammals the primitive colour-pattern was that of stripes1 either longitudinal or transverse and more probably the former4 ,in the second stage these bands break up into spots1 which still show the longitudinal arrangement and may be either light on a dark ground1 or dark on a light ground4 ,in a third stage the spots may again coalesce into stripes1 the course of which is at right angles to that of the original stripes1 or the spots may disappear1 leaving a uniform body-colour1 lighter or white on the belly4 ,these changes of colour-pattern have not proceeded at a uniform rate in the various mammalian groups1 or even within the same group1 for an all-important factor is the mode of life of the particular animal4 ,in general1 it may be said that the scheme of colour is such as to render its possessor inconspicuous1 or even invisible1 and many a creature that seems to be very conspicuous and striking in a museum case can hardly be seen at all when in its natural surroundings4 ,thus1 ,arctic mammals and birds1 in their winter dress1 are white2 desert animals are tawny or sandy-brown2 forest animals are frequently striped or spotted2 while those that live on open plains are more commonly of uniform colouration4 ,there are exceptions to these rules1 but they hold good for the most part4 ,from careful comparative study of the teeth and skeletons a clew may be gained as to the habits of animals and from the habits something may be inferred as to the colouration4 ,illustration3 ,,fig4 #f4--,tapirus terrestris1 #c days old4 ,compare with ,fig4 #acg1 p4 #cbj4 7,by permission of ,w4 ,s4 ,berridge1 ,london47 ,it would1 however1 be misleading to claim a greater authority for these attempts at restoring a long-vanished life than can fairly be ascribed to them4 ,the general form and proportions of the head1 neck1 body1 tail1 limbs and feet may be deduced with a high degree of accuracy from the skeleton1 while the external characters of skin1 hair and colouration are largely conjectural1 but not altogether imaginary4 ,it cannot be doubted that among the extinct mammals were many which1 owing to some uncommon growth of subcutaneous fat1 or some unusual local development of hair1 were much more curious and bizarre in appearance than we can venture to represent them4 ,if1 for example1 the ,camel1 the ,horse1 the ,lion and the ,right ,whale were extinct and known only from their skeletons1 such restorations as we could make of them would assuredly go astray in some particulars4 ,the ,camel would be pictured without his hump1 for there is nothing in the skeleton to suggest it2 the forelock1 mane and characteristic tail of the ,horse and the ,lion's mane would certainly not be recognized2 while the immense development of blubber in the head of the ,whale gives to it a very different appearance from that which the skull would seem to indicate4 ,such cases are1 however1 exceptional and restorations made by competent hands from complete skeletons probably give a fair notion of the appearance of those animals when alive4 ,it will thus be sufficiently plain that the work of restoration is beset with difficulties1 but that there is no good ground for the uncritical scepticism which summarily rejects the results as being purely fanciful1 or for the equally uncritical credulity which unhesitatingly accepts them as fully and incontestably accurate4 ,it is altogether likely that one of the main sources of error consists in making the extinct animal too closely resemble some existing species which is selected as a model4 ,too much space has perhaps been devoted to the problem of restoring the external form of these extinct mammals1 a problem which1 after all1 is of distinctly subordinate importance4 ,the most valuable results which may be gained from a study of these fossil mammals are the answers which they afford to the great questions of relationship1 classification and genetic descent1 and the light which they throw upon the processes of evolution and the course of geographical arrangement4 ,the bones and teeth afford admirable means of tracing the gradual steps of modification by which the modern mammals have arisen from very different ancestors and of following their wanderings from region to region and continent to continent4 ,it is to these questions that most of the subsequent chapters are devoted4 ,,chapter ,,iii ,,the ,,classification ,,of ,,the ,,mammalia ,the terminology and nomenclature of science form a great barrier1 which only too often shuts out the educated layman from following the course of investigation and keeping abreast of the discoveries in which he may be particularly interested4 ,no more frequent and heartfelt complaint is uttered than that which decries the 8scientific jargon10 and one might be tempted to think that this jargon was a superfluous nuisance1 deliberately adopted to exclude the uninitiated and guard the secrets of the temple from the curious intruder4 ,as a matter of fact1 however1 this terminology1 though an unquestionable evil from one point of view1 is an indispensable implement of investigation and description4 ,ordinary language has far too few words for the purpose and most of the words that might be used lack the all-important quality of precision4 ,the vernacular names of animals and plants are notoriously inexact and1 even when not inaccurately employed1 are not sufficiently refined and distinctive for scientific use4 ,this is pre-eminently true of the ,new ,world1 where the ,european settlers gave the names of the creatures with which they had been familiar at home to the new animals which they found in the western hemisphere4 ,some of these names1 such as deer1 wolf1 fox1 bear1 are accurate enough for ordinary purposes1 while others are ludicrously wrong4 ,the bird that we call the ,robin is altogether different from his ,european namesake1 and the great stag1 or ,wapiti1 is commonly called 8,elk10 a name which properly belongs to the ,moose4 ,in short1 it is impossible to gain the necessary accuracy and abundance of vocabulary without devising an artificial terminology1 drawn chiefly from ,greek and ,latin4 ,in dealing with fossils1 the difficulty of nomenclature becomes formidable indeed4 ,the larger and more conspicuous mammals of the modern world are more or less familiar to all educated people1 and such names as rhinoceros1 hippopotamus1 elephant1 kangaroo1 will call up a definite and fairly accurate image of the animal in question4 ,for the strange creatures that vanished from the earth ages before the appearance of ,man there are no vernacular names and it serves no good purpose to coin such terms4 ,to the layman names like ,uintatherium or ,smilodon convey no idea whatever1 and all that can be done is to attempt to give them a meaning by illustration and description1 using the name merely as a peg upon which to hang the description4 ,the system of zological classification which is still in use was largely the invention of the ,swedish naturalist ,linnus1 who published it shortly after the middle of the eighteenth century4 ,as devised by ,linnus1 the scheme was intended to express ideal relationships1 whereas now it is employed to express real genetic affinities1 so far as these can be ascertained4 ,the ,linnan system is an organized hierarchy of groups1 arranged in ascending order of comprehensiveness4 ,in this scheme1 what may be regarded as the unit is the species1 a concept around which many battles have been waged and concerning which there is still much difference of opinion and usage4 ,originally a term in logic1 it first received a definite meaning in ,zology and ,botany from ,john ,ray 7#afbh-agje7 who applied it to indicate a group of animals1 or plants1 with marked common characters and freely interbreeding4 ,linnus1 though not always consistent in his expressions on the subject1 regarded species as objective realities1 concrete and actual things1 which it was the naturalist's business to discover and name1 and held that they were fixed entities which had been separately created4 ,this belief in the fixity and objective reality of species was almost universally held1 until the publication of ,darwin's 8,origin of ,species0 7#ahei7 converted the biological world to the evolutionary faith1 which declares that the only objective reality among living things is the individual animal or plant4 ,according to this modern conception1 a species may be defined as signifying a 8grade or rank assigned by systematists to an assemblage of organic forms which they judge to be more closely interrelated by common descent than they are related to forms judged to be outside the species0 7,p4 ,chalmers ,mitchell74 ,the technical name of a species1 which is either in ,latin1 or in latinized form1 is in two words1 one of which designates the genus 7see below7 and the other the particular species of that genus1 as1 for example1 ,equus caballus1 the species ,horse1 ,e4 przewalskii1 the ,asiatic ,wild ,horse1 ,e4 asinus1 the species ,ass1 etc4 ,in order to identify a species1 the genus to which it belongs must be stated1 hence the term1 binomial system of nomenclature1 which ,linnus introduced1 becoming trinomial when the name of a subspecies is added1 a modern refinement on the older method4 ,a very large species 7i4e4 one which is represented by great numbers of individuals71 extending over a very large area1 is often divisible into groups of minor rank1 as varieties1 geographical races or subspecies4 ,taking the species as the unit in the scheme of classification1 the varieties and subspecies may be considered as fractions4 ,there is great difference of usage among writers on systematic zology in the manner of applying the generally accepted concept of species1 some making their groups very much more comprehensive than others1 according as they are 8lumpers0 or 8splitters10 to employ the slang phrase4 ,the difficulty lies in the fact that there are no fixed and definite criteria1 by which a given series of individuals can be surely distinguished as a variety1 a species or a genus2 it is a matter for the judgment and experience of the systematist himself4 ,the individuals of a species may differ quite widely among themselves1 provided that they are all connected by intergradations1 and the more or less constant varieties or subspecies are to be distinguished from the individual variants1 which are inconstant and fluctuating4 ,no two specimens agree exactly in every particular1 but if a very large suite of them be compared1 it will be found that the great majority depart but little from the average or norm of the species1 and the wider the departure from the norm1 the fewer the individuals which are so aberrant4 ,taking so easily measured a character as size1 for example1 and measuring several hundred or a thousand representatives of some species1 we see that a large majority are of average size1 a little more or a little less1 while very large or very small individuals are rare in proportion to the amount by which they exceed or fall short of the norm4 ,subspecies or varieties are marked by differences which are relatively constant1 but not of sufficient importance to entitle them to rank as species4 ,a group of the second rank is called a genus1 which may contain few or many species1 or only a single one4 ,in the latter case the species is so isolated in character that it cannot properly be included in the same genus with any other species4 ,a large genus1 one containing numerous species1 is frequently divisible into several subgenera1 each comprising a group of species which are more similar to one another than they are to the other species of the genus4 ,the third of the main groups in ascending order is the family1 which ordinarily consists of a number of genera united by the possession of certain common characters1 which1 at the same time1 distinguish them from other genera1 though a single isolated genus may require a separate family for its reception4 ,just as it is often convenient to divide a genus into subgenera1 so families containing many genera are usually divisible into subfamilies1 as indicative of closer relationships within the family4 ,the name of the family is formed from that of the genus first described or best known1 with the termination -id1 while that for the subfamily is -in4 ,to take an example1 all the genera of cats1 living and extinct1 are assembled in the family ,felid 7from the genus ,felis7 which falls naturally into two subfamilies4 ,one of these1 the ,felin1 includes the true cats1 a very homogeneous group1 both the existing and the extinct genera2 the other subfamily1 that of the highly interesting series of the 8,sabre-tooth ,tigers10 called the ,machairodontin1 comprises only extinct forms4 ,the fourth principal rank or grade is the order1 distinguished by some fundamental peculiarity of structure and usually including a large number of families4 ,some of the orders1 however1 contain but a single family1 a single genus1 or even1 it may be1 a single species1 because that species is in important structural characters so unlike any other that it cannot properly be put into the same order with anything else4 ,such isolation invariably implies that the species or genus in question is the sole survivor of what was once an extensive series4 ,as in the case of the family and the genus1 it is often necessary to recognize the degrees of closer and more remote affinity by the use of suborders4 ,existing ,artiodactyla1 or even-toed hoofed animals1 an enormous assemblage1 may conveniently be divided into four suborders3 7#a7 ,suina1 swine and the ,hippopotamus2 7#b7 ,tylopoda1 the ,camel and ,llama2 7#c7 ,tragulina1 8mouse-deer10 or chevrotains2 7#d7 ,pecora1 or true ruminants1 deer1 giraffes1 antelopes1 sheep1 goats1 oxen1 etc4 ,in nearly all of the orders such subordinal divisions are desirable and it is frequently useful to employ still further subdivisions1 like superfamilies1 which are groups of allied families within the suborder1 sections and the like4 ,in the ,linnan scheme1 the next group in ascending rank is the class1 which includes all mammals whatsoever1 but the advance of knowledge has made it necessary to interpolate several intermediate grades between the class and the order1 which1 in the descending scale1 are subclass1 infraclass1 cohort1 superorder and others1 while above the class comes the subkingdom of ,vertebrata1 or animals with internal skeletons1 which includes mammals1 birds1 reptiles1 amphibians and fishes4 ,a word should be said as to the conventions of printing technical names4 ,the names of all species are1 in ,american practice1 printed in small letters1 but many ,europeans write specific terms which are proper nouns or adjectives with a capital4 ,generic1 family and all groups of higher rank are always written with a capital1 unless used in vernacular form1 e4g4 ,artiodactyla and artiodactyls4 ,it is also a very general custom to give capitals to vernacular names of species1 as the ,mammoth1 the ,coyote1 the ,black ,bear4 ,genus and species are almost invariably in italics1 groups of higher rank in roman4 ,such a scheme of classification as is outlined above has a decidedly artificial air about it and yet it serves a highly useful purpose in enabling us to express in brief and condensed form what is known or surmised as to the mutual relationships of the great and diversified assemblage of mammals4 ,the scheme has been compared to the organization of an army into company1 battalion1 regiment1 brigade1 division1 army corps1 etc41 and there is a certain obvious likeness2 but the differences go deeper1 for an army is an assemblage of similar units1 mechanically grouped into bodies of equal size4 ,a much closer analogy is the genealogical or family tree1 which graphically expresses the relationships and ramifications of an ancient and widespread family1 though even this analogy may easily be pushed too far4 ,blood-relationship is1 in short1 the underlying principle of all schemes of classification which postulate the theory of evolution4 ,the system of ,linnus1 as expanded and improved by modern zologists1 has proved itself to be admirably adapted to the study of the living world2 but it is much more difficult to apply it to the fossils1 for they introduce a third dimension1 so to speak1 for which the system was not designed4 ,this third dimension is the successive modification in time of a genetically connected series4 ,the cumulative effect of such modifications is so great that only very elastic definitions will include the earlier and later members of an unbroken series4 ,in attempting to apply the ,linnan system to the successive faunas 7i4e4 assemblages of animals7 which have inhabited the earth1 palontologists have employed various devices4 ,one such method is to classify each fauna without reference to those which precede and follow it1 but this has the great drawback of obscuring and ignoring the relationships1 to express which is the very object of classification4 ,another and more logical method is to treat species and genera as though they belonged to the present order of things1 for these groups1 particularly species1 were relatively short-lived1 when regarded from the standpoint of geological time1 and either became so modified as to require recognition as new species and genera1 or died out without leaving descendants4 ,groups of higher rank1 families1 orders1 etc41 are treated as genetic series and include the principal line or stock and such side-branches as did not ramify too widely or depart too far from the main stem4 ,under the first arrangement1 the horses1 a long history of which has been deciphered1 would be divided into several families2 under the second1 they are all included in a single family4 ,one of the most interesting results of palontological study is the discovery that in many families1 such as the horses1 rhinoceroses and camels1 there are distinct series which independently passed through parallel courses of development1 the series of each family keeping a remarkably even pace in the degree of progressive modification4 ,such a minor genetic series within a family is called a phylum1 not a very happy selection1 for the same term had been previously employed in a much wider sense1 as equivalent to the subkingdom4 ,in both uses of the term the underlying principle1 that of genetic series1 is the same2 the difference is in the comprehensiveness of meaning4 ,it must be admitted that no method1 yet devised1 of applying the ,linnan scheme to the fossils is altogether satisfactory1 and indeed it is only the breaks and gaps in the palontological record which makes possible any use of the scheme4 ,could we obtain approximately complete series of all the animals that have ever lived upon the earth1 it would be necessary to invent some entirely new scheme of classification in order to express their mutual relationships4 ,in the present state of knowledge1 classification can be made only in a preliminary and tentative sort of way and no doubt differs widely from that which will eventually be reached4 ,so far as the mammals are concerned1 part of the problem would seem to be quite easy and part altogether uncertain4 ,some mammalian groups appear to be well defined and entirely natural assemblages of related forms1 while others are plainly heterogeneous and artificial1 yet there is no better way of dealing with them until their history has been ascertained4 ,the mutual relations of the grand groups1 or orders1 are still very largely obscure4 ,the class ,mammalia is first of all divided into two subclasses of very unequal size4 ,of these1 the first1 ,,prototheria1 is represented in the modern world by few forms1 the so-called ,duck-billed ,mole 7,ornithorhynchus paradoxus7 and ,spiny ,anteaters 7,echidna7 of ,australia4 ,they are the lowest and most primitive of the mammals and retain several structural characters of the lower vertebrates4 ,their most striking characteristic is that the young are not brought forth alive1 but are hatched from eggs1 as in the reptiles1 birds and lower vertebrates generally4 ,the second subclass1 ,,eutheria1 which includes all other mammals1 is again divided into two very unequal groups or infraclasses4 ,one of these1 ,,didelphia1 contains but a single order1 the ,marsupialia1 or pouched mammals1 now in existence1 and is also very primitive in many respects1 though far more advanced than the ,prototheria4 ,the young1 though born alive1 are brought forth in a very immature state and1 with the exception of one genus 7,perameles7 the ftus is not attached by a special structure1 the placenta1 to the womb of the mother4 ,like the ,prototheria1 the ,marsupials1 which were once spread all over the world1 are at present almost entirely confined to ,australia and the adjoining islands1 the ,opossums of ,north and ,south ,america1 and one small genus 7,cnolestes7 in the latter continent being the exceptions to this rule of distribution4 ,the second and vastly larger infraclass1 the ,,monodelphia1 is characterized by the placenta1 a special growth1 partly of ftal and partly of maternal origin1 by means of which the unborn young are attached to the mother and nourished during the ftal period2 they are born in a relatively mature state and are generally able to walk immediately after birth and resemble their parents in nearly all respects4 ,the vast assemblage of placental mammals1 which range over all the continents1 are divided into numerous orders1 most of which appear to be natural groups of truly related forms1 while some are but doubtfully so and others again are clearly unnatural and arbitrary4 ,as has already been pointed out1 the mutual relationships of these orders1 as expressed in groups of higher than ordinal rank1 offer a much more difficult problem1 chiefly because our knowledge of the history of mammals is most deficient just where that history is most important and significant1 namely1 in its earlier portion4 ,in many instances1 the evolution of genera and families may be followed out within the limits of the order in a very convincing way1 but very rarely can the origin of an order be demonstrated4 ,when the history began to be full and detailed1 the orders had nearly all been established1 and1 until the steps of their divergence and differentiation can be followed out1 their mutual relationships can be discussed only from the standpoint of their likenesses and differences4 ,in the valuation of these1 there is much room for difference of opinion1 and such difference is not lacking4 ,on the other hand1 concerning the number and limits of the orders themselves there is very general agreement4 ,in the following table only the major groups are included and those which are extinct are marked with a dagger 774 ,the scheme is almost identical with that given in ,professor ,osborn's 8,age of ,mammals10 the few points in which ,i should prefer a somewhat different arrangement being waived in the interests of uniformity and avoidance of confusion4 ,a few changes are1 however1 made in matters which ,i regard as too important to ignore4 ,i4 ,,subclass ,,prototheria4 ,egg-laying ,mammals4 #a4 ,,order ,,protodonta4 #b4 ,,order ,,monotremata1 e4g4 the ,duck-billed ,mole and ,spiny ,anteaters4 ,,ii4 ,,subclass ,,eutheria4 ,viviparous ,mammals4 ,a4 ,,infraclass ,,didelphia4 ,pouched ,mammals4 #a4 ,,order ,,triconodonta4 #b4 ,,order ,,marsupialia4 a4 ,,suborder ,polyprotodonta4 ,opossums1 carnivorous and insectivorous ,marsupials4 b4 ,,suborder ,diprotodonta4 ,herbivorous ,marsupials2 ,kangaroos1 etc4 c4 ,,suborder ,allotheria4 ,b4 ,,infraclass ,,monodelphia4 ,placental ,mammals4 ,,aa4 ,,cohort ,,unguiculata4 ,clawed ,mammals4 #a4 ,,order ,,trituberculata4 #b4 ,,order ,,insectivora4 ,insect-eating ,mammals4 a4 ,,suborder ,lipotyphla1 e4g4 ,moles1 ,hedgehogs1 ,shrews1 etc4 b4 ,,suborder ,hyopsodonta4 c4 ,,suborder ,proglires4 d4 ,suborder ,menotyphla1 e4g4 ,tree and ,jumping ,shrews4 #c4 ,,order ,,tillodontia4 #d4 ,,order ,,dermoptera4 ,the ,flying ,lemur4 #e4 ,,order ,,chiroptera4 ,bats4 #f4 ,,order ,,carnivora4 ,beasts of ,prey4 a4 ,,suborder ,creodonta4 ,primitive ,flesh-eaters4 b4 ,,suborder ,fissipedia4 ,wolves1 ,bears1 ,weasels1 ,cats1 etc4 c4 ,,suborder ,pinnipedia4 ,marine ,carnivores--,seals and ,walruses4 #g4 ,,order ,,rodentia4 ,gnawing ,mammals4 a4 ,,suborder ,duplicidentata1 e4g4 ,hares1 ,rabbits1 ,pikas4 b4 ,,suborder ,simplicidentata1 e4g4 ,squirrels1 ,marmots1 ,beavers1 ,rats1 ,mice1 ,porcupines1 etc4 #h4 ,,order ,t,,niodontia4 #i4 ,,order ,,edentata4 a4 ,,suborder ,pilosa4 ,hairy ,edentates1 e4g4 ,sloths1 ,anteaters1 etc4 b4 ,,suborder ,loricata4 ,armoured ,edentates1 e4g4 ,armadillos1 ,glyptodonts4 #aj4 ,,order ,,pholidota4 ,scaly ,anteaters or ,pangolins4 #aa4 ,,order ,,tubulidentata4 ,the ,aard ,vark4 ,,bb4 ,,cohort ,,primates4 ,mammals with nails4 #ab4 ,,order ,,primates4 a4 ,,suborder ,lemuroidea4 ,lemurs4 b4 ,,suborder ,anthropoidea4 ,monkeys1 ,apes1 ,man4 ,,cc4 ,,cohort ,,ungulata4 ,hoofed ,mammals4 #ac4 ,,order ,,condylarthra4 #ad4 ,,order ,,amblypoda4 #ae4 ,,order ,,artiodactyla4 ,even-toed ,hoofed ,mammals4 a4 ,,suborder ,artiodactyla ,primitiva4 b4 ,,suborder ,suina4 ,swine1 ,peccary1 ,hippopotamus4 c4 ,,suborder ,tylopoda4 ,camels1 ,llama1 ,guanaco4 d4 ,,suborder ,tragulina4 ,mouse-deer or ,chevrotains4 e4 ,,suborder ,pecora1 e4g4 ,deer1 ,antelopes1 ,sheep1 ,oxen1 etc4 #af4 ,,order ,,perissodactyla4 ,odd-toed ,hoofed ,mammals4 a4 ,,suborder ,chelodactyla1 e4g4 ,horses1 ,tapirs1 ,rhinoceroses1 etc4 b4 ,,suborder ,ancylopoda4 ,chalicotheres4 #ag4 ,,order ,,proboscidea4 ,elephants and ,mastodons4 #ah4 ,,order ,,barytheria4 #ai4 ,,order ,,embrithopoda4 #bj4 ,,order ,,sirenia4 ,sea-cows and ,dugongs4 #ba4 ,,order ,,hyracoidea4 ,conies4 #bb4 ,,order ,,toxodontia4 a4 ,,suborder ,toxodonta4 b4 ,,suborder ,typotheria4 c4 ,,suborder ,entelonychia4 d4 ,,suborder ,pyrotheria4 #bc4 ,,order ,,astrapotheria4 #bd4 ,,order ,,litopterna4 ,,dd4 ,,cohort ,,cetacea4 ,whales1 ,dolphins1 ,porpoises4 #be4 ,,order ,,zeuglodontia4 #bf4 ,,order ,,odontoceti4 ,toothed ,whales1 ,dolphins1 ,porpoises4 #bg4 ,,order ,,mystacoceti4 ,whalebone ,whales4 ,,chapter ,,iv ,,the ,,skeleton ,,and ,,teeth ,,of ,,mammals ,with very rare exceptions1 and those only of the latest geological period 7,quaternary71 the fossil remains of mammals consist only of bones and teeth4 ,the evolutionary changes1 so far as these are preserved1 are recorded therefore in terms of dental and skeletal modifications4 ,to render these changes intelligible1 it is necessary to give some account of the mammalian skeleton and teeth1 with no more use of technical language than is unavoidable2 ordinary speech does not furnish a sufficient number of terms1 nor are most of these sufficiently precise4 ,with the aid of the figures1 the reader may easily gain a knowledge of the skeleton which is quite adequate for the discussion of fossil series1 which will follow in the subsequent chapters4 ,i4 ,,the ,,skeleton ,i4 ,the most obvious distinction of the skeletal parts is into axial and appendicular portions1 the former comprising the skull1 backbone or vertebral column1 ribs and breast-bone or sternum1 and the latter including the limb-girdles1 limbs and feet4 ,in the axial skeleton only the ribs and certain bones of the skull are paired1 but in the appendicular all the bones are in pairs1 for the right and left sides respectively4 ,illustration3 ,,fig4 #g4--,skull of ,wolf 7,canis occidentalis74 ,p4,mx41 premaxillary4 ,mx41 maxillary4 ,na41 nasal4 ,l41 lachrymal4 ,ma41 malar or jugal4 ,fr41 frontal4 ,pa41 parietal4 ,sq41 squamosal4 ,zyg41 zygomatic process of squamosal4 ,o4,s41 orbitosphenoid4 ,pl41 palatine4 ,m41 mandible4 cor41 coronoid process of mandible4 m4c41 condyle of mandible4 ang41 angular process of mandible4 p4g41 postglenoid process of squamosal4 ,ty41 tympanic 7auditory bulla74 mas41 mastoid4 p4oc41 paroccipital process4 con41 occipital condyle4 ,ex4,o41 exoccipital4 ,s4,o41 supraoccipital4 ,the skull is a highly complex structure1 made up of many parts1 most of which are immovably fixed together1 and performing many functions of supreme importance4 ,in the first place1 it affords secure lodgement and protection for the brain and higher organs of sense1 those of smell1 sight and hearing1 and second1 it carries the teeth and1 by its movable jaws1 enables these to bite1 to take in and masticate food4 ,the portion of the skull which carries the brain1 eyes and ears1 is called the cranium1 and the portion in front of this is the face1 the boundary between the two being an oblique line drawn immediately in front of the eye-socket 7,fig4 #g74 ,a great deal of the endless variety in the form of the skull of different mammals depends upon the differing proportions of cranium and face4 ,in the human skull1 for example1 the cranium is enormously developed and forms a great dome1 while the face is shortened almost to the limit of possibility2 the skull of the ,horse1 on the other hand1 goes to nearly the opposite extreme of elongation of the facial and shortening of the cranial region4 ,the posterior surface of the skull1 or occiput1 is made up of four bones1 which in most adult mammals are fused into a single occipital bone4 ,at the base of the occiput is a large opening1 the foramen magnum1 through which the spinal cord passes to its junction with the brain2 and on each side of the opening is a large1 smooth1 oval prominence1 the occipital condyles1 by means of which the skull is articulated with the neck4 ,the paroccipital processes are bony styles of varying length1 which are given off1 one on each side external to the condyles4 ,the boundary of the occiput is marked by a ridge1 the occipital crest1 which varies greatly in prominence1 but is very well marked in the more primitive forms and tends to disappear in the more highly specialized ones4 ,the roof and much of the sides of the cranium are formed by two pairs of large bones1 the parietals behind and the frontals in advance2 along the median line of the cranial roof1 where the two parietals meet1 is usually another ridge1 the sagittal crest1 which joins the occipital crest behind4 ,the sagittal crest also varies greatly in prominence1 being in some mammals very high and in others entirely absent1 and1 like the occipital crest1 is a primitive character2 as a rule1 it is longest and highest in those mammals which have the smallest brain-capacity4 ,as pointed out by ,professor ,leche1 the development of the sagittal crest is conditioned by the relative proportions of the brain-case and the jaws4 ,powerful jaws and a small brain-case necessitate the presence of the crest1 in order to provide sufficient surface of attachment for the temporal muscles1 which are important in mastication1 while with large brain-case and weak jaws the crest is superfluous4 ,though the brain-case proper may be quite small1 yet it may have its surface enormously increased by great thickening of the cranial bones1 as is true of elephants and rhinoceroses1 and in them sufficient surface for attachment is afforded to the muscles without the development of a crest4 ,illustration3 ,,fig4 #h4--,skull of ,wolf1 top view4 ,p4,mx41 premaxillary4 ,na41 nasal4 ,ma41 malar or jugal4 ,l41 lachrymal4 ,fr41 frontal4 ,sq41 squamosal4 ,pa41 parietal4 ,s4,o41 supraoccipital4 ,illustration3 ,,fig4 #i4--,skull of ,wolf1 view of base4 ,p4,mx41 premaxillary4 ,mx41 palatine process of maxillary4 ,pl41 palatine4 ,fr41 frontal4 ,pt41 parietal4 ,ma41 malar or jugal4 ,sq41 glenoid cavity of squamosal4 ,b4,s41 basisphenoid4 ,b4,o41 basioccipital4 ,ty41 tympanic 7auditory bulla74 p4oc41 paroccipital process4 con41 occipital condyle4 ,s4,o41 supraoccipital4 ,the structure of these cranial bones1 more particularly of the parietals1 is subject to important changes2 in most mammals they are of moderate thickness and have dense layers1 or 8tables10 forming the outer and inner surfaces and1 between these1 a layer of spongy bone4 ,in many large mammals1 however1 especially those which have heavy horns or tusks1 the cranial bones become enormously thick and the spongy layer is converted into a series of communicating chambers1 or sinuses1 the partitions between which serve as braces1 thus making the bone very strong in proportion to its weight4 ,sinuses are very generally present in the frontals and communicate by small openings with the nasal passage1 even in genera of moderate size and without horns or tusks4 ,the frontals form the roof of the eye-sockets1 or orbits1 and usually there is a projection from each frontal1 which marks the hinder border of the orbit and is therefore called the postorbital process4 ,the roof of the facial region is made by the nasals1 which are commonly long and narrow bones1 but vary greatly in form and proportions in different mammals2 in those which have a proboscis1 like tapirs and elephants1 or a much inflated snout1 such as the ,moose 7,alce7 or the ,saiga ,antelope 7,saiga tatarica7 the nasals are always very much shortened and otherwise modified in form4 ,the anterior end of the skull is formed by a pair of rather small bones1 the premaxillaries1 which carry the incisor teeth2 they bound the sides of the nasal opening1 or anterior nares1 reaching to the nasals1 when the latter are of ordinary length2 they also form the front end of the hard or bony palate1 which divides the nasal passage from the mouth4 ,the maxillaries1 or upper jaw-bones1 make up nearly all of the facial region on each side and send inward to the median line from each side a bony plate which together constitute the greater part of the hard palate2 the remainder of the upper teeth are implanted in the maxillaries4 ,a varying proportion of the hinder part of the hard palate is formed by the palatines1 which also enclose the posterior nares1 the opening by which the nasal passage enters the back part of the mouth4 ,the maxillary of each side extends back to the orbit1 which it bounds anteriorly and in the antero-superior border of which is the usually small lachrymal4 ,the inferior1 and more or less of the anterior1 border of the orbit is made by the cheek-bone 7malar or jugal7 which may or may not have a postorbital process extending up toward that of the frontal2 when the two processes meet1 the orbit is completely encircled by bone1 but only in monkeys1 apes and ,man is there a bony plate given off from the inner side of the postorbital processes1 which extends to the cranial wall and converts the orbit into a funnel-shaped cavity4 ,for most of its length1 the jugal projects freely outward from the side of the skull and extends posteriorly beneath a similar bar of bone1 the zygomatic process of the squamosal4 ,this process and the jugal together constitute the zygomatic arch1 which on each side of the skull stands out more or less boldly1 and the size and thickness of which are subject to great variation in different mammals1 the massiveness of the arch being proportional to the power of the jaws4 ,one of the principal muscles of mastication 7the masseter7 is attached to the zygomatic arch4 ,the squamosal itself is a large plate1 which makes up a great part of the side-wall of the cranium and articulates above with the frontal and parietal2 it also supports the lower jaw1 the articular surface for which is called the glenoid cavity4 ,the lower jaw is held in place by the postglenoid process1 which is a projection1 usually a transverse ridge1 behind the cavity4 ,back of the postglenoid process is the entrance to the middle ear1 the auditory meatus1 which may be merely an irregular hole1 or a more or less elongated tube4 ,the meatus is an opening into the tympanic1 a bone which at birth is a mere ring and in some mammals remains permanently in that condition1 but as a rule develops into a swollen1 olive-shaped auditory bulla1 which sometimes reaches enormous proportions1 especially in nocturnal mammals4 ,the labyrinth of the internal ear is contained in the periotic1 a very dense bone which is concealed in the interior of the cranium1 but in many mammals a portion of it1 the mastoid1 is exposed on the surface between the squamosal and occipital4 ,the lower jaw-bone 7inferior maxillary1 or mandible7 is the only freely movable element of the skull2 it consists of two halves which meet anteriorly at the chin in a contact of greater or less length1 called the symphysis4 ,in nearly all young mammals and in many adult forms the two halves of the lower jaw are separate and are held together at the symphysis only by ligaments1 while in others1 as in ,man1 they are indistinguishably fused to form a single bone4 ,each half consists of two portions1 a horizontal part or ramus and an ascending ramus or vertical part2 the former supports all of the lower teeth1 and its length1 depth and thickness are very largely conditioned by the number and size of those teeth4 ,the ascending ramus is a broad1 rather thin plate1 divided at the upper end into two portions1 the hinder one of which terminates in the condyle1 a rounded1 usually semicylindrical projection1 which fits into the glenoid cavity of the squamosal4 ,the anterior portion of the ascending ramus ends above in the coronoid process1 which serves for the insertion of the temporal muscle1 the upper portion of which is attached to the walls of the cranium and thus1 when the muscle is contracted1 the jaws are firmly closed2 the coronoid process passes inside of the zygomatic arch4 ,the lower jaw is therefore a lever of the third order1 in which the power is applied between the weight 7i4e4 the food1 the resistance of which is to be overcome7 and the fulcrum1 which is the condyle4 ,at the postero-inferior end of the ascending ramus is the angle1 the form of which is characteristically modified in the various mammalian orders and is thus employed for purposes of classification4 ,the hyoid arch is a ,u-shaped series of small and slender bones1 with an unpaired element closing the arch below2 each vertical arm of the ,u is attached to the tympanic of its own side and the whole forms a flexible support for the tongue1 but with no freely movable joint like that between the lower jaw and the squamosal4 ,the mammalian skull in its primitive form may be thought of as a tube divided into two parts1 of which the hinder one is the brain-chamber1 or cranial cavity1 and the forward one the nasal chamber or passage4 ,with the growth of the brain and consequent enlargement of the cranium1 this tubular character is lost2 and various modifications of the teeth1 jaws and facial region1 the development of horns and tusks1 bring about the many changes which the skull has undergone4 ,this brief sketch of the skull-structure is very incomplete1 several of its elements having been altogether omitted and only those parts described which are needful in working out the history and descent of the various mammalian groups4 ,the second portion of the axial skeleton is the backbone1 or vertebral column1 which is made up of a number of separate bones called vertebr4 ,these are so articulated together as to permit the necessary amount of flexibility and yet retain the indispensable degree of strength4 ,the function of the backbone is a twofold one3 7#a7 to afford a firm support to the body and give points of attachment to the limbs1 and 7#b7 to carry the spinal cord1 or great central axis of the nervous system1 in such a manner that it shall be protected against injury1 a matter of absolutely vital necessity4 ,while the vertebr differ greatly in form and appearance in the various regions of the neck1 body and tail1 in adaptation to the various degrees of mobility and strength which are required of them1 yet they are all constituted upon the same easily recognizable plan4 ,the principal mass of bone in each vertebra is the body1 or centrum1 which is typically a cylinder1 or modification of that form1 and the two ends of the cylinder are the faces1 by which the successive vertebr are in contact with one another4 ,in the living animal1 however1 the successive centra are not in actual contact1 but are separated by disks of cartilage 7gristle7 which greatly add to the elasticity of the column4 ,from the upper surface of the centrum arises an arch of bone1 the neural arch1 enclosing with the centrum the neural canal1 through which runs the spinal cord4 ,as already mentioned1 the protection of the spinal cord is essential to the life of the animal1 yet this protection must be combined with a certain flexibility1 both lateral and vertical4 ,mere contact of the centra1 even though these be held in place by ligaments1 would not give the column strength to endure1 without dislocation1 the great muscular stresses which are put upon it4 ,additional means of articulation between the successive vertebr are therefore provided1 and these vary in size1 form and position in different regions of the backbone1 in nice adjustment to the amount of motion and degree of strength needed at any particular part of the column4 ,of these additional means of articulation1 which are called the zygapophyses1 each vertebra has two pairs1 an anterior and a posterior pair1 placed upon the neural arch4 ,from the summit of the arch arises the neural spine1 a more or less nearly straight rod or plate of bone1 which may be enormously long or extremely short1 massive or slender1 in accordance with the muscular attachments which must be provided for4 ,finally1 should be mentioned the transverse processes1 rod-like or plate-like projections of bone1 which arise1 one on each side of the vertebra1 usually from the centrum1 less commonly from the neural arch2 these also differ greatly in form and size in the various regions of the column4 ,anatomists distinguish several other processes of the vertebra1 but for our purpose it is not necessary to take these into consideration4 ,illustration3 ,,fig4 #aj4--;,first dorsal vertebra of ,wolf from the front4 cn41 centrum4 r41 facet for the head of the rib4 r41 facet for the tubercle of the rib4 tr41 transverse process4 pr4z41 anterior zygapophyses4 n4sp41 neural spine4 ,five different regions of the backbone may be distinguished1 in each of which the vertebr are modified in a characteristic way4 ,there is 7#a7 the cervical region1 or neck1 the vertebr of which1 among mammals 7with only one or two exceptions7 are always seven in number1 however long or short the neck may be2 the immoderately long neck of the ,giraffe has no more and the almost invisible neck of the ,whale has no less1 and thus the elongation of the neck is accomplished by lengthening the individual vertebr and not by increasing their number4 7#b7 ,those vertebr to which ribs are attached are named dorsal or thoracic and can always be recognized by the pits or articular facets which receive the heads of the ribs4 7#c7 ,behind the dorsal is the lumbar region1 or that of the loins1 made up of a number of vertebr which carry no ribs4 ,the dorso-lumbars are known collectively as the trunk-vertebr and are generally quite constant in number for a given group of mammals1 though often differently divided between the two regions in different members of the same group4 ,in the ,artiodactyla1 for example1 there are very constantly #ai trunk-vertebr1 but the ,hippopotamus has #ae dorsals and #d lumbars1 the ,reindeer 7,rangifer7 #ad ,d41 #e ,l41 the ,ox 7,bos taurus7 #ac ,d41 #f ,l41 the ,camel 7,camelus dromedarius7 #ab ,d4 and #g ,l4 7#d7 ,next follows the sacrum1 which consists of a varying number of coalesced vertebr4 ,the number of sacral vertebr varies from #b to #ac1 but is usually from #c to #e4 7#e7 ,finally1 there are the caudal vertebr1 or those of the tail1 which are extremely variable in number and size1 depending upon the length and thickness of the tail4 ,we must next consider briefly some of the structural features which characterize the vertebr of the different regions4 7#a7 ,the length of the neck varies greatly in different mammals and1 up to a certain point1 flexibility increases with length1 but1 as the number of #g cervicals is almost universally constant among mammals and the lengthening of the neck is accomplished by an elongation of the individual vertebr1 a point is eventually reached1 where greater length is accompanied by a diminution of mobility4 ,for instance1 in the ,giraffe the movements of the neck are rather stiff and awkward1 in striking contrast to the graceful flexibility of the ,swan's neck1 which has #bc vertebr1 more than three times as many4 ,illustration3 ,,fig4 #aa4--;,atlas of ,wolf1 anterior end and left side4 cot41 anterior cotyles4 n4c41 neural canal4 n4a41 neural arch4 tr41 transverse process4 v4a41 posterior opening of the canal for the vertebral artery4 ,the first two cervical vertebr are especially and peculiarly modified1 in order to support the skull and give to it the necessary degree of mobility upon the neck4 ,the first vertebra1 or atlas1 is hardly more than a ring of bone with a pair of oval1 cuplike depressions 7anterior cotyles7 upon the anterior face 7superior in ,man7 into which are fitted the occipital condyles of the skull4 ,by the rolling of the condyles upon the atlas is effected the nodding movement of the head1 upward and downward1 but not from side to side2 this latter movement is accomplished by the partial rotation of skull and atlas together upon the second vertebra in a manner presently to be explained4 ,on the hinder aspect are two articular surfaces 7posterior cotyles7 in shape like the anterior pair1 but very much less concave1 which are in contact with corresponding surfaces on the second vertebra4 ,the neural arch of the atlas is broad and low and the neural canal is apparently much too large for the spinal cord1 but1 in fact1 only a part of the circular opening belongs to the neural canal4 ,in life1 the opening is divided by a transverse ligament into an upper portion1 the true neural canal1 and a lower portion1 which lodges a projection from the second vertebra4 ,the atlas usually has no neural spine and never a prominent one2 the transverse processes are broad1 wing-like plates and each is perforated by a small canal1 which transmits the vertebral artery4 ,illustration3 ,,fig4 #ab4--;,axis of ,wolf1 left side4 od4p4 odontoid process4 cot41 anterior cotyles4 n4a41 neural arch4 n4sp41 neural spine4 pt4z41 posterior zygapophyses4 tr41 transverse process4 v4a41 anterior opening of canal for the vertebral artery4 v4a41 posterior opening of the same4 ,the second vertebra1 or axis1 is a little more like the ordinary vertebra1 having a definite and usually elongate centrum1 on the anterior end of which are the two articular surfaces for the atlas4 ,between these is a prominent projection1 the odontoid process1 which fits into the ring of the atlas and has a special articulation with the lower bar of that ring4 ,in most mammals the odontoid process is a bluntly conical peg1 varying merely in length and thickness1 but in many long-necked forms the peg is converted into a semicylindrical spout1 convex on the lower side and concave above4 ,the neural spine of the axis is almost always a relatively large1 hatchet-shaped plate1 which is most developed in the carnivorous forms1 and the transverse processes are commonly slender rods4 ,the five succeeding cervical vertebr are much alike1 though each one has a certain individuality1 by which its place in the series may readily be determined4 ,the centrum has a convex anterior and concave posterior face1 which in long-necked animals form regular 8ball and socket0 joints2 neural spines are frequently wanting and1 when present1 are almost always short and slender2 the zygapophyses are very prominent and are carried on projections which extend before and behind the neural arch2 the transverse processes are long1 thin plates and1 except in the seventh cervical1 are usually pierced by the canal for the vertebral artery1 but in a few forms 7e4g4 the camels7 this canal pierces the neural arch4 7#b7 ,the dorsal or thoracic vertebr have more or less cylindrical centra1 with nearly flat faces1 and on the centra1 for the most part at their ends1 are the concave facets for the rib-heads4 ,the transverse processes are short and rod-like and most of them articulate with the tubercles of the ribs4 ,the zygapophyses are smaller than in the cervical region1 less prominent and less oblique2 the anterior pair1 on the front of the neural arch1 face upward and the posterior pair downward4 ,the neural spines are very much longer than those of the neck and those of the anterior dorsals are often of relatively enormous length1 diminishing toward the hinder part of the region4 ,illustration3 ,,fig4 #ac4--;,fifth cervical vertebra of ,wolf1 left side4 tr41 transverse process4 v4a41 posterior opening of canal for the vertebral artery4 pr4z4 and pt4z41 anterior and posterior zygapophyses4 n4sp41 neural spine4 ,illustration3 ,,fig4 #ad4--;,first dorsal vertebra of ,wolf1 left side4 c41 centrum4 r41 anterior rib-facet4 r41 posterior rib-facet4 tr41 transverse process4 pr4z4 pt4z41 anterior and posterior zygapophyses4 n4sp41 neural spine4 7#c7 ,the lumbar vertebr are almost always heavier and larger than those of the dorsal region2 they carry no ribs and their neural spines and transverse processes are broad and plate-like and the latter are far larger and more prominent than those of the dorsals4 ,as an especial degree of strength is frequently called for in the loins1 together with a greater flexibility than is needed in the dorsal region1 the modes of articulation between the successive vertebr are more complex1 sometimes1 as in the ,edentata1 most elaborately so4 ,taking the dorso-lumbars1 or trunk-vertebr1 as a single series1 we may note that in a few mammals 7e4g4 the elephants7 all the neural spines have a backward slope1 but in the great majority of forms this backward inclination ceases near the hinder end of the dorsal region1 where there is one vertebra with erect spine1 while behind this point the spines slope forward4 ,illustration3 ,,fig4 #ae4--,third lumbar vertebra of ,wolf1 front end and left side4 tr41 transverse process4 cn41 centrum4 pr4z4 and pt4z41 anterior and posterior zygapophyses4 n4sp41 neural spine4 7#d7 ,the sacral vertebr1 varying from #b to #ac in number1 are fused together solidly into one piece1 the combined centra forming a heavy mass and the neural canals a continuous tube1 while the neural spines are united into a ridge4 ,as a rule1 only the first two vertebr of the sacrum are in contact with the hip-bones1 to support which they have developed special processes1 the remainder of the mass projecting freely backward4 ,illustration3 ,,fig4 #af4--,sacrum of ,wolf1 upper side4 ,i1 ,,ii1 ,,iii1 first1 second and third sacral vertebr4 pl41 surface for attachment to hip-bone4 ,illustration3 ,,fig4 #ag4--;,caudal vertebr of ,wolf1 from anterior and middle parts of the tail4 ,letters as in ,fig4 #ae4 7#e7 ,the caudal vertebr vary greatly1 in accordance with the length and thickness of the tail4 ,in an animal with well-developed tail several of the anterior caudals have the parts and processes of a typical vertebra1 centrum1 neural arch and spine1 zygapophyses and transverse processes4 ,posteriorly1 these gradually diminish1 until only the centrum is left1 with low knobs or ridges1 which are the remnants of the various processes4 ,a varying number of long1 cylindrical centra1 diminishing backward in length and diameter1 complete the caudal region and the vertebral column4 ,in some mammals1 chevron bones are attached to the under side of the anterior and middle caudals2 these are forked1 ,y-shaped bones1 which form a canal for the transmission of the great blood-vessels of the tail4 ,illustration3 ,,fig4 #ah4--,ribs of ,wolf from anterior and middle parts of the thorax4 cp41 head1 t41 tubercle4 ,the ribs1 which are movably attached to the backbone1 together with the dorsal vertebr and breast-bone1 compose the thorax1 or chest4 ,the articulation with the vertebr is by means of a rounded head2 in most cases the head has two distinct facets1 the pit being formed half on the hinder border of one dorsal vertebra and half on the front border of the next succeeding one1 but posteriorly the pit is often shifted1 so as to be on a single vertebra4 ,a second articulation is by means of the tubercle1 a smooth projecting facet on the convexity of the rib's curvature and near the head2 the tubercle articulates with the transverse process of its vertebra4 ,the ribs1 in general1 are curved bars of bone1 which in small mammals generally and in the clawed orders are slender and rod-like1 while in the hoofed mammals they are broader1 thinner and more plate-like1 especially the anterior ones4 ,the number of pairs of ribs is most commonly #ac1 but ranges among existing mammals from #i in certain whales to #bd in the ,two-toed ,sloth 7,cholpus didactylus74 ,the complex curvature of the ribs1 outward and backward1 is such that1 when they are drawn forward 7in ,man upward7 by muscular action1 the cavity of the thorax is enlarged and air is drawn into the lungs1 and when they are allowed to fall back1 the cavity is diminished and the air expelled4 ,below1 a varying number of the ribs are connected by the cartilages in which they terminate with the breast-bone 7sternum72 sometimes these cartilages are ossified and then form the sternal ribs1 but there is always a flexible joint between the latter and the true ribs4 ,in certain edentates1 notably the anteaters and the extinct ground-sloths1 these sternal ribs1 at their lower ends1 are provided with head and tubercle1 for articulation with the sternum4 ,the sternum1 or breast-bone1 is made up of a number of distinct segments1 usually broad and flat1 but often cylindrical1 which may unite1 but far more commonly remain separate throughout life4 ,the number1 size and form of these segments often give useful characters in classification4 ,the first segment1 or manubrium1 has quite a different shape from the succeeding ones and is considerably longer4 ,illustration3 ,,fig4 #ai4--,sternum and rib-cartilages of ,wolf1 lower side4 ,p4,s41 manubrium4 ,x4,s41 xiphisternum4 ,,ii4 ,the appendicular skeleton consists of the limb-girdles and the bones of the limbs and feet4 ,the limb-girdles are the means of attaching the movable limbs to the body1 so as to combine the necessary mobility with strength4 ,the anterior1 or shoulder-girdle1 has no direct articulation with the vertebral column1 but is held in place by muscles2 it is made up of the shoulder-blade and collar-bone1 though very many mammals have lost the latter4 ,illustration3 ,,fig4 #bj4--,left scapula of ,wolf4 gl41 glenoid cavity4 c41 coracoid4 ac41 acromion4 sp4 spine4 ,illustration3 ,,fig4 #ba4--,left scapula of ,horse4 ,this figure is much more reduced than ,fig4 #bj4 ,illustration3 ,,fig4 #bb4--,left scapula of ,man in position of walking on all fours4 ,letters as in ,fig4 #bj4 ,the shoulder-blade1 or scapula1 is a broad1 thin1 plate-like bone1 which contracts below to a much narrower neck1 ending in a concave articular surface1 the glenoid cavity1 for the head of the upper arm-bone1 the two together making the shoulder-joint4 ,on the outer side the blade is divided into two parts by a prominent ridge1 the spine1 which typically ends below in a more or less conspicuous projection1 the acromion1 which may1 however1 be absent1 its prominence being1 generally speaking1 correlated with the presence of the collar bone4 ,a hook-like process1 the coracoid1 rises from the antero-internal side of the glenoid cavity and varies greatly in size in the different groups of mammals2 though it usually appears to be merely a process of the scapula1 with which it is indistinguishably fused1 yet its development shows it to be a separate element and in the lowest mammals 7,prototheria71 as in the reptiles and lower vertebrates generally1 it is a large and important part of the shoulder-girdle and articulates with the sternum4 ,the collar-bone1 or clavicle1 is a complexly curved bar1 which1 when present and fully developed1 extends from the forward end of the sternum to the acromion1 the projecting lower end of the scapular spine1 supporting and strengthening the shoulder-joint4 ,in many mammalian orders1 notably all existing hoofed animals1 the clavicle has become superfluous and is lost more or less completely2 it may be said1 in general1 that the clavicle is developed in proportion to the freedom of motion of the shoulder-joint and to the power of rotation of the hand upon the arm4 ,in arboreal animals1 such as monkeys1 in which the hand rotates freely and the arm moves in any direction on the shoulder1 the clavicle is large and fully developed1 as it also is in ,man4 ,many burrowing mammals 7e4g4 the moles7 have very stout clavicles4 ,illustration3 ,,fig4 #bc4--,left clavicle of ,man1 front side4 ,illustration3 ,,fig4 #bd4--,left hip-bone of ,wolf4 ,il41 ilium4 ,is41 ischium4 ,p41 pubis4 ac41 acetabulum4 ,the posterior1 or pelvic1 girdle is composed on each side of a very large1 irregularly shaped bone1 which is firmly attached to one or more of the coalesced vertebr which form the sacrum and thus affords a solid support to the hind leg4 ,each half of the pelvis1 or hip-bone1 is made up of three elements1 called respectively the ilium1 ischium and pubis1 which are separate in the very young animal1 indistinguishably fused in the adult4 ,the three elements unite in a deep1 hemispherical pit1 the acetabulum1 which receives the head of the thigh-bone1 a perfect example of the 8ball and socket joint40 ,in the inferior median line the two pubes meet and may become coalesced1 in a symphysis1 the length of which differs in various mammals4 ,the pelvis and sacrum together form a short1 wide tube1 the diameter of which is normally greater in the female skeleton than in the male4 ,the limbs are each divided into three segments1 which in the anterior extremity are the arm1 fore-arm and hand 7or fore foot7 and in the posterior extremity are the thigh1 leg and foot 7or hind foot71 and there is a general correspondence between the structure of these segments in the fore and hind legs1 however great the superficial difference4 ,the bones of the limbs1 as distinguished from those of the feet1 are the long bones and1 except in a few very large and heavy mammals1 are essentially hollow cylinders1 thus affording the maximum strength for a given weight of bone2 the cavity of a long bone contains the marrow and hence is called the medullary cavity4 ,in the young mammal each of the long bones consists of three parts1 the shaft1 which makes up much the greater part of the length1 and at each end a bony cap1 the epiphysis4 ,growth takes place by the intercalation of new material between the shaft and the epiphyses2 when the three parts unite1 growth ceases and the animal is adult4 ,illustration3 ,,fig4 #be4--,left humerus of ,wolf1 from the front and outer sides1 the latter somewhat oblique4 h41 head4 int4t41 internal tuberosity4 ext4t41 external tuberosity4 bc41 bicipital groove4 dt41 deltoid ridge4 sh41 shaft4 s41 supinator ridge4 int4 epi41 internal epicondyle4 s4f41 anconeal foramen4 tr41 trochlea4 tr41 trochlea1 posterior side4 ext4 epi41 external epicondyle4 a4f41 anconeal fossa4 ,illustration3 ,,fig4 #bf4--,left humerus of ,horse1 front side4 i4t41 internal tuberosity4 ex4t41 external tuberosity4 bc41 outer part of bicipital groove4 dt41 deltoid ridge4 s41 supinator ridge4 tr41 trochlea4 ,illustration3 ,,fig4 #bg4--,left humerus of ,man1 front side4 ,letters as in ,fig4 #be4 ,the superior segment of the fore limb has a single bone1 the humerus1 the upper end of which is the rounded1 convex head1 which fits into the glenoid cavity of the shoulder-blade1 forming the joint of the shoulder2 in front of the head are two prominent and sometimes very large projections for muscular attachment1 the external and internal tuberosities1 separated by a groove1 in which play the two tendons of the biceps muscle and is therefore called the bicipital groove4 ,in a few mammals1 such as the ,horse1 ,camel and ,giraffe1 the groove is divided into two by a median tubercle or ridge4 ,from the external tuberosity there generally passes down the front face of the shaft a rough and sometimes very prominent ridge1 the deltoid crest1 to which is attached the powerful deltoid muscle4 ,at the lower end of the humerus is the trochlea1 an irregular half-cylinder1 for articulation with the two bones of the fore-arm and varying in form according to the relative sizes of those bones4 ,on each side of the trochlea is frequently a rough prominence1 the epicondyle1 and above the inner one is1 in many mammals1 a perforation1 the epicondylar foramen1 for the passage of a nerve4 ,extending up the shaft from the outer epicondyle is a rough crest1 the supinator ridge1 to which is attached one of the muscles that rotate the hand and is conspicuously developed in those mammals which have the power of more or less free rotation and especially in burrowers4 ,on the posterior face of the humerus1 just above the trochlea1 is a large1 deep pit1 the anconeal fossa4 ,illustration3 ,,fig4 #bh4--,left fore-arm bones of ,wolf1 front side4 ,r41 radius4 ,u41 ulna4 ol41 olecranon4 h41 head of radius4 ,illustration3 ,,fig4 #bi4--,left fore-arm bones of ,man1 front side4 ,letters as in ,fig4 #bh4 ,the small object at the right of each figure is the head of the radius1 seen from above4 ,the two bones of the fore-arm1 the radius and ulna1 are1 in most mammals1 entirely separate from each other1 but in certain of the more highly specialized hoofed animals are immovably cossified4 ,primitively1 the two bones were of nearly equal size1 but in most of the mammalian orders there is a more or less well-defined tendency for the radius to enlarge at the expense of the ulna4 ,these bones are normally crossed1 the radius being external at the upper end and passing in front of the ulna to the inner side of the arm4 ,the radius varies considerably in form in accordance with the uses to which the hand is put2 if the capacity of rotation is retained1 the upper end1 or head1 of the radius is small1 circular or disk-like1 covering little of the humeral trochlea1 but when the head of the radius is broadened to cover the whole width of the humerus1 then all power of rotation is lost4 7,cf4 ,figs4 #bh and #bi47 ,as a rule1 the radius broadens downward and covers two-thirds or more of the breadth of the wrist-bones4 ,illustration3 ,,fig4 #cj4--;,cossified bones of left fore-arm of ,horse1 front side4 ,for most of its length1 the ulna is concealed by the radius4 ,illustration3 ,,fig4 #ca4--,left fore-arm bones of the ,tapir 7,tapirus terrestris74 ,r41 radius4 ,u41 ulna4 h41 head of radius4 h41 sigmoid notch of ulna4 ol41 olecranon4 ,n4,b4 ,this figure is on a much larger scale than ,fig4 #cj4 ,the ulna is longer than the radius1 its upper end being extended into a heavy process1 the olecranon1 or anconeal process1 into which is inserted the tendon of the great triceps muscle1 the contraction of which straightens the arm2 this process is the bony projection at the back of the elbow-joint4 ,below the olecranon is a semicircular articular concavity1 which embraces the humeral trochlea and its upper angle fits into the anconeal fossa of the humerus4 ,the ulna contracts and grows more slender downwards and its lower end covers but one of the wrist-bones4 ,while in the more primitive mammals1 and in those which retain the power of rotating the hand1 the ulna has nearly or quite the same thickness as the radius1 it is often much more slender and in the more highly specialized of the hoofed animals1 such as the horses1 camels and true ruminants1 the radius carries the entire weight and the ulna has become very slender1 more or less of its middle portion is lost and the two ends are cossified with the radius1 so that the fore-arm appears to have but a single bone4 ,the reverse process of enlarging the ulna and reducing the radius is very rare and practically confined to the elephant tribe4 ,illustration3 ,,fig4 #cb4--,left manus of ,wolf1 front side4 ,,sl41 scapho-lunar4 ,py41 pyramidal4 ,pis41 pisiform4 ,tm41 trapezium4 ,td41 trapezoid4 ,m41 magnum4 ,u41 unciform4 ,mc4 ,i-,v1 first to fifth metacarpals4 ,ph4 #a1 first phalanx4 ,ph4 #b1 second phalanx4 ,ung41 ungual phalanx4 ,i1 first digit1 or pollex4 ,,ii-,v1 second to fifth digits4 ,illustration3 ,,fig4 #cc4--,left manus of ,man4 ,s41 scaphoid4 ,l41 lunar4 ,py41 pyramidal 7pisiform not shown74 ,tm41 trapezium4 ,td41 trapezoid4 ,m41 magnum4 ,un41 unciform4 ,the fore foot1 or hand1 for which the term manus may be conveniently employed1 is divisible into three parts1 corresponding in ourselves to the wrist1 back and palm of the hand1 and the fingers4 ,the bones of the wrist constitute the carpus1 those of the back and palm the metacarpus1 and those of the fingers the phalanges4 ,the carpus consists primitively of nine distinct bones1 though one of these1 as will be shown later1 is not a true carpal4 ,these bones are of a rounded1 subangular shape1 closely appressed together1 with very little movement between them1 and are arranged in two transverse rows4 ,the upper row contains four bones1 which enumerating from the inner side are the scaphoid1 lunar1 pyramidal 7or cuneiform7 and pisiform4 ,the scaphoid and lunar support the radius1 while the ulna rests upon the pyramidal4 ,the pisiform1 though very constantly present1 is not a true carpal1 but an ossification in the tendon of one of the flexor muscles1 which close the fingers2 it projects more or less prominently backward and articulates with the ulna and pyramidal4 ,the second row is also made up of four bones1 which1 from within outward1 are the trapezium1 trapezoid1 magnum and unciform4 ,the relations of the two rows vary much in different mammals and the arrangement may be serial or alternating2 thus1 the scaphoid rests upon the trapezium and trapezoid and usually covers part of the magnum2 the lunar may rest upon the magnum only1 but very much more frequently is equally supported by the magnum and unciform and the pyramidal by the latter only4 ,the ninth carpal is the central1 which1 when present and distinct1 is a small bone1 wedged in between the two rows4 ,few existing mammals have a separate central1 which1 though present in the embryo1 has coalesced with the scaphoid in the great majority of forms4 ,in the more advanced and differentiated mammals the number of carpals may be considerably reduced by the cossification of certain elements or the complete suppression and loss of others4 ,in all existing ,carnivora and a few other mammals the scaphoid and lunar are united in a compound element1 the scapho-lunar 7or1 more accurately1 the scapho-lunar-central72 hoofed animals with a diminished number of toes generally lose the trapezium1 and other combinations occur4 ,the second row of carpals carries the metacarpals1 and primitively the trapezium1 trapezoid and magnum are attached each to one metacarpal and the unciform has two4 ,the metacarpus consists typically of five members1 a number which is never exceeded in any normal terrestrial mammal2 the members are numbered from the inner side1 beginning with the thumb or pollex1 from ,i to ,v4 ,many mammals have fewer than five metacarpals1 which may number four1 three1 two or only one2 the third is never lost1 but any or all of the others may be suppressed1 and functionless rudiments of them may long persist as splints or nodules4 ,the metacarpals are elongate1 relatively slender and of more or less cylindrical shape2 but the form varies considerably in different groups1 according to the way in which the hand is used4 ,when employed for grasping1 as in many arboreal animals and pre-eminently in ,man1 the pollex is frequently opposable to the other fingers and enjoys much freedom of motion4 ,in the camels and true ruminants the third and fourth metacarpals are cossified to form a cannon-bone 7see ,fig4 #dc1 p4 #ia71 but the marrow cavities and the joints for the phalanges remain separate4 ,the phalanges in land mammals never exceed three in each digit1 except the pollex1 which1 when present and fully developed1 has but two4 ,the phalanges are usually slender in proportion to their length1 but in very heavy hoofed animals they are short and massive4 ,the terminal joint is the ungual phalanx1 which carries the nail1 claw1 or hoof1 its shape varying accordingly4 ,illustration3 ,,fig4 #cd4--,left femur of ,wolf1 front side4 h41 head4 gt4tr41 great trochanter4 tr4 #b1 second trochanter4 int4 con41 internal condyle4 r4g41 rotular groove1 ext4 con41 external condyle4 ,illustration3 ,,fig4 #ce4--,left femur of ,horse4 tr4 #c1 third trochanter4 ,other letters as in ,fig4 #cd1 than which this drawing is very much more reduced4 ,the hind leg is constituted in very much the same manner as the fore1 but with certain well-marked and constant differences4 ,the thigh-bone1 or femur1 is usually the longest and stoutest of the limb-bones and in very large animals may be extremely massive4 ,at the upper end is the hemispherical head1 which is set upon a distinct neck and projects inward and upward1 fitting into the acetabulum of the hip-bone4 ,nearly all land mammals have a small pit on the head of the femur1 in which is inserted one end of the round ligament1 while the other end is attached in a corresponding depression in the floor of the acetabulum4 ,this ligament helps to hold the thigh-bone firmly in place and yet allows the necessary freedom of movement4 ,on the outer side of the upper end of the femur is a large1 roughened protuberance1 which often rises higher than the head and is called the great trochanter2 another1 the second or lesser trochanter1 is a small1 more or less conical prominence on the inner side of the shaft1 below the head4 ,these two processes are well-nigh universal among land mammals2 and in a few of the orders occurs the third trochanter1 which arises from the outer side of the shaft1 usually at or above the middle of its length4 ,though comparatively rare in the modern world1 the third trochanter is an important feature1 and the early members of most1 if not all1 of the mammalian orders possessed it4 ,the shaft of the femur is elongate and1 except in certain very bulky mammals1 of nearly cylindrical shape4 ,the lower end of the bone is thick and heavy and bears on the posterior side two large1 rounded prominences1 the condyles1 which articulate with the shin-bone to form the knee-joint4 ,on the anterior side is a broad1 shallow groove1 the rotular groove1 in which glides the patella1 or knee-cap4 ,the patella is a large ossification1 of varying shape1 in the tendon common to the four great extensor muscles of the thigh1 the action of which is to straighten the leg4 ,illustration3 ,,fig4 #cf4--,left femur of ,wolf1 inside of lower end4 ext4 con41 external condyle4 int4 con41 internal condyle4 r4g41 rotular groove4 ,above1 are two views of the left patella1 anterior and internal sides4 ,the lower leg1 like the fore-arm1 has two bones1 which1 however1 are always parallel1 never crossed1 and have no power of rotation4 ,of these1 the inner one is the shin-bone1 or tibia1 which is always the larger and alone enters into the knee-joint4 ,the external bone is the fibula1 which is almost entirely suppressed in certain highly specialized forms1 such as the horses and ruminants1 the tibia carrying the whole weight4 ,the upper end of the tibia is enlarged and extends over that of the fibula2 it has two slightly concave surfaces for articulation with the condyles of the femur1 the approximate edges of which are raised into a bifid spine4 ,the upper part of the shaft is triangular1 with one edge directed forward1 and the superior end of this edge is roughened and thickened to form the cnemial crest1 to which is attached the patellar ligament4 ,the middle portion of the shaft is rounded and the lower end broad and usually divided by a ridge into two grooves or concavities for the ankle-bone2 from the inner side of this end projects downward a tongue-like process1 the internal malleolus1 which prevents inward dislocation of the ankle4 ,the fibula is relatively stoutest in the less advanced mammals and is usually straight and slender1 with enlarged ends1 the lower one forming the external malleolus1 which serves to prevent outward dislocation of the ankle4 ,in many forms the fibula is cossified with the tibia at both ends1 and in the most highly specialized hoofed animals1 such as the horses1 camels and true ruminants1 the bone has apparently disappeared4 ,the young animal1 however1 shows that the ends of the fibula have been retained and the shaft completely lost2 the upper end is in the adult firmly fused with the tibia and1 in the horses1 the lower end is also1 but this remains separate in the ruminants and camels1 forming the malleolar bone1 which is wedged in between the tibia and the heel-bone4 ,because of its importance in holding the ankle-bone in place1 this lower end of the fibula is never lost in any land mammal4 ,illustration3 ,,fig4 #cg4--;,bones of left lower leg of ,wolf1 front side4 ,t41 tibia4 ,f41 fibula4 sp4 spine of tibia4 cn4 cnemial crest4 i4m41 internal malleolus4 e4m41 external malleolus4 ,illustration3 ,,fig4 #ch4--;,bones of left lower leg of ,horse 7much more reduced74 cn4 cnemial crest4 ,f41 lower end of fibula1 cossified with tibia4 ,other letters as in ,fig4 #cg4 ,illustration3 ,,fig4 #ci4--;,bones of lower leg1 left side1 of ,tapir4 ,t41 tibia4 ,f41 fibula4 sp41 spine of tibia4 cn41 cnemial crest4 i4m41 internal malleolus4 e4m41 external malleolus4 ,n4,b4 ,this figure is on a much larger scale than ,fig4 #ch4 ,illustration3 ,,fig4 #dj4--,left pes of ,wolf1 front side4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,ch41 cuboid4 ,cn4 #a1 ,cn4 #b1 ,cn4 #c1 internal1 middle and external cuneiforms4 ,mt4 ,i1 rudimentary first metatarsal4 ,mt4 ,,ii-,v1 second to fifth metatarsals4 ,ph4 #a1 first phalanx4 ,ph4 #b1 second phalanx4 ,ung41 ungual phalanx4 ,i1 rudimentary hallux4 ,,ii-,v1 second to fifth digits4 ,illustration3 ,,fig4 #da4--,left pes of ,man4 ,note the large size of ,mt4 ,i1 the metatarsal of the first digit1 or hallux4 ,letters as in ,fig4 #dj1 except ,cb41 cuboid4 ,the hind foot1 or pes1 like the manus1 is clearly divisible into three parts1 the bones of which are called respectively the tarsus1 metatarsus and phalanges1 and the correspondence in structure between manus and pes is close and obvious4 ,the tarsus consists typically of seven bones1 which are tightly packed and rarely permit any movement between them4 ,the upper row of the tarsus consists of two bones1 which are peculiarly modified to form the ankle-joint and heel2 on the inner side is the ankle-bone1 or astragalus1 the shape of which is highly characteristic of the various mammalian orders4 ,the upper or posterior portion of the astragalus1 according to the position of the foot1 is a pulley which glides upon the lower end of the tibia and is held firmly in place by the internal and the external malleolus4 ,below the pulley-like surface the astragalus usually contracts to a narrow neck1 which ends in a flat or convex head4 ,the astragalus is supported behind 7or beneath7 by the heel-bone1 or calcaneum1 which is elongate and extends well above 7or behind7 the remainder of the tarsus2 it frequently has a distinct articulation with the fibula1 but more commonly is not in contact with that bone4 ,the astragalus rests upon the navicular1 which is moulded to fit its head and corresponds in position to the central of the carpus1 but1 unlike that carpal1 it is a very important element and is never suppressed or lost in any land mammal4 ,the navicular1 in turn1 rests upon three bones of the second row1 which are called respectively the internal1 middle and external cuneiform1 which correspond to the trapezium1 trapezoid and magnum of the carpus and to which are attached the three inner metatarsals1 one to each4 ,finally1 the cuboid1 the external element of the second row1 is a large bone1 which supports the calcaneum and often part of the astragalus and to which the fourth and fifth metatarsals are attached2 it is the equivalent of the unciform in the manus4 ,the number of tarsals is more constant than that of the carpals1 but some suppressions and cossifications do occur4 ,the long bones of the pes constitute the metatarsus1 which is the counterpart of the metacarpus4 ,there are never more than five metatarsals in any normal mammal1 but there may be any number less than five1 down to a single one4 ,in form and size the metatarsals of any given mammal are usually so like the metacarpals1 that it requires some experience to distinguish them1 but when either manus or pes is especially adapted to some particular kind of work1 there may be very decided differences between metatarsals and metacarpals4 ,for example1 the burrowing forefoot of the moles is very different from the hind foot1 which has undergone but little modification1 and even more striking is the difference between the wing of a bat and its foot4 ,many other instances of a less extreme divergence might be enumerated1 but when manus and pes are used only for locomotion1 as in nearly all hoofed animals and many other mammals1 the metacarpals and metatarsals are very similar4 ,when there is a difference in number1 it is the general rule that there are fewer metatarsals2 an instance of this is found in the tapirs1 which have four toes in the front foot and three in the hind4 ,forms which have a cannon-bone in the manus have it also in the pes1 and some1 like the peccaries and the jumping rodents called jerboas1 have it only in the pes4 ,the first 7or inner7 metatarsal1 that of the great toe1 or hallux1 is sometimes opposable to the others1 as in the monkeys1 apes and lemurs4 ,the word metapodial is a useful general term which includes both metacarpals and metatarsals4 ,a metapodial with its phalanges is a digit1 a term often employed because of the ambiguity which arises in the use of the words 8fingers0 and 8toes10 and is applicable to both fore and hind feet4 ,normally1 the phalanges of the pes are so like those of the manus as to require no particular description2 and only when the two pairs of extremities are specialized for entirely different functions1 is there any notable divergence between the phalanges of manus and pes4 ,illustration3 ,,fig4 #db4--,left pes of ,black ,bear 7,ursus americanus71 showing the plantigrade gait4 ,t41 tibia4 ,f41 fibula4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cn4 #c1 external cuneiform4 ,cb41 cuboid4 ,mt4 ,v41 fifth metatarsal4 ,illustration3 ,,fig4 #dc4--,left pes of ,patagonian ,deer 7,hippocamelus bisulcus71 showing the unguligrade gait4 ,t41 tibia4 ,f41 lower end of fibula 7malleolar bone74 ,cal41 calcaneum4 ,as41 astragalus4 ,n4,cb41 cossified cuboid and navicular4 ,mt4 ,,iii1 ,mt4 ,,iv1 cannon-bone1 formed by the cossification of the third and fourth metatarsals4 ,v41 ,rudimentary fifth digit4 ,before leaving the subject of the skeleton1 it will be well to explain the terms used in describing the gait and manner of using the feet4 ,when the entire sole of the foot is in contact with the ground and weight is thrown upon the heel-bone1 or calcaneum1 the gait is said to be plantigrade and is exemplified in ,man1 bears1 raccoons and many other mammals4 ,the ,dog is digitigrade1 that is to say1 the feet in the standing position are nearly erect and the wrist and heel are raised high above the ground2 the weight is borne upon ball-like pads1 one under the phalanges of each functional digit and one under the metapodials4 ,the digitigrade gait is found not only in all the dogs and cats1 but in many other ,carnivora and in the camels and llamas1 as well4 ,transitions between the plantigrade and digitigrade gait are so numerous and gradual1 that such terms as semi-plantigrade and semi-digitigrade are sometimes necessary4 ,an animal is said to be unguligrade when the weight is carried entirely upon the hoofs and is used only of hoofed animals2 examples are the horses1 pigs1 deer1 antelopes1 oxen1 etc4 ,the so-called 8knee0 of a horse is really his wrist and the 8hock0 is the heel1 so that the feet make nearly half the apparent length of the legs4 ,certain very large and massive animals1 such as the rhinoceroses and elephants1 are unguligrade in a modified sense2 the foot is a heavy column1 seemingly a part of the leg1 and the weight is borne upon a great pad of elastic tissue1 with the hoofs disposed around its periphery4 ,a very peculiar mode of locomotion is exemplified by certain of the ,edentata1 in the forefoot of the existing ,ant ,bear 7,myrmecophaga jubata7 and in both extremities of some of the later representatives of the extinct ground-sloths1 or ,gravigrada4 ,here the weight is carried upon the outer edge of the foot1 the palm and sole being turned inward4 ,no term has been suggested for this very exceptional gait1 which is a modified form of plantigradism4 ,,ii4 ,,the ,,teeth ,it was pointed out in ,chapter ,,ii 7p4 #ch7 that very often the teeth are all that remains to us of extinct genera and species of mammals1 and it may be further noted that the teeth are very characteristic and often suffice to fix the systematic position of a genus4 ,since1 therefore1 the teeth play such an uncommonly important part as fossils and are so pre-eminently useful to the palontologist1 it is necessary to give some general account of them4 ,among the mammals the teeth display a very great variety of size and form in accordance with the manner in which they are used4 ,primarily1 the function of the teeth is to seize and masticate food1 and the kind of food habitually eaten by any animal is well indicated by the form of its teeth4 ,the beasts of prey have teeth adapted for shearing flesh and crushing bones2 plant-feeders have teeth fitted for cropping plants and triturating vegetable tissues2 insect-eaters have teeth with numerous sharp-pointed cusps1 or it may be1 no teeth at all1 swallowing without mastication the insects which they capture1 etc4 ,among animals that have similar diet there is very great difference in the form and elaborateness of the grinding apparatus and it is often possible to follow out the steps of evolutionary change1 by which1 from simple beginnings1 a high degree of complexity has been attained4 ,in addition to the uses of the teeth as organs of mastication1 they frequently serve as weapons of offence or defence4 ,in the flesh-eaters which capture living prey they are formidable offensive weapons1 and the fangs of the ,lion or the ,wolf are instances familiar to every one2 but the tusks of the elephants or the hippopotamuses have nothing to do with the taking of prey4 ,several ,old ,world deer1 which have no antlers or very small ones1 possess scimitar-like upper tusks1 with which they are able to defend themselves very effectually4 ,in the lower vertebrates1 such as reptiles and fishes1 the number of teeth is usually indefinite and they continue to be shed and replaced1 as needed1 throughout life2 but in each species of mammal1 aside from abnormalities1 the number is fixed and constant4 ,mammalian teeth are very generally divisible into four categories3 7#a7 the incisors1 or front teeth1 which in the upper jaw are inserted in the premaxillary bones1 7#b7 the canines1 or eye-teeth1 which are never more than one on each side of each jaw1 or four in all1 7#c7 the premolars1 called in ,man the bicuspids1 the anterior grinding teeth which have predecessors in the milk-series and 7#d7 the molars1 the posterior grinding teeth which have no such predecessors4 ,illustration3 ,,fig4 #dd4--;,dentition of ,wolf1 left side4 i4 #c1 third incisor4 ,c41 canine4 p4 #a1 first premolar4 p4 #d1 fourth premolar4 m4 #a1 first molar4 ,it is customary and convenient to express the numbers and kinds of teeth of a given mammalian species by means of a 8dental formula02 for example1 in ,man the formula is3 i #b_/b1 c #a_/a1 p #b_/b1 m #c_/c1 #b #cb2 the reason for the multiplication by two is that the figures deal only with one side of the mouth and must be doubled to give the sum total4 ,just because1 however1 the two sides are alike1 it is usual to take the doubling for granted4 ,written out in full1 the formula means that ,man has two incisors1 one canine1 two premolars and three molars on each side of each jaw1 the horizontal line indicating the division between upper and lower teeth4 ,the number of teeth is frequently not the same in the upper and lower jaws2 for instance1 the formula for the ,sheep is3 i #j_/c1 c #j_/a1 p #c_/c1 m #c_/c1 #b #cb2 the total is the same as in ,man1 but the arrangement is entirely different4 ,the meaning is that in the ,sheep there are no upper incisors or canines1 but three incisors and a canine are present in each half of the lower jaw1 with three premolars and three molars on each side above and below4 ,the ,dog gives still another formula3 i #c_/c1 c #a_/a1 p #d_/d1 m #b_/c1 #b #db4 ,what is called the typical formula for the higher terrestrial mammals above the grade of the marsupials and which is but rarely exceeded1 is i #c_/c1 c #a_/a1 p #d_/d1 m #c_/c1 #b #dd1 though most existing mammals have fewer teeth than this4 ,compared with the typical formula1 the ,dog has lost but two teeth1 the third upper molar on each side1 while ,man and the ,sheep have each lost twelve4 ,as every one knows from his own experience1 mammals normally have two sets of teeth1 the first1 temporary1 or milk-dentition1 in the young animal1 and the second1 or permanent dentition1 in the adult4 ,the milk-dentition1 when fully developed1 consists of incisors1 canines and premolars1 which usually agree in number1 though often not in form1 with the permanent teeth which replace them in the adult4 ,the milk-teeth are frequently more conservative than the permanent ones and retain ancestral characters which have disappeared in the adult series1 thus affording welcome information as to lines of descent and steps of evolutionary change4 ,while there can be little doubt that the development of more than one dentition1 or set of teeth1 is the primitive condition among mammals and was derived by inheritance from their lower vertebrate ancestors1 in which there was an indefinite succession of teeth2 yet there are many mammals in which the milk-dentition is greatly reduced or altogether lost4 ,in some1 the milk-teeth are shed and replaced before birth1 in others only the germs of the milk-teeth are formed and never cut the gum1 while in others again all traces of the temporary series have vanished4 ,this complete loss of the milk-teeth1 like the presence of a great number of simple and similar teeth in the dolphins and porpoises1 or the total absence of teeth1 as in the anteaters and whalebone whales1 is a secondary and derivative condition1 never a primitive one4 ,illustration3 ,,fig4 #dd;,a4--,first upper molar1 right side of ,deer 7,odocoileus74 ,on the left1 the masticating surface2 heavy black line1 enamel4 ,on the right1 external side1 showing crown and roots4 ,brachyodont4 ,illustration3 ,,fig4 #de4--;,first upper molar1 left side1 of a fossil horse 7,equus sp474 ,on the right1 external side4 ,on the left1 the grinding surface1 showing two stages of wear4 ,heavy black line1 enamel2 white1 dentine2 shaded1 cement4 ,hypsodont1 roots not yet formed4 ,the structure of mammalian teeth varies greatly1 from the simplest slender cones to enormous and highly complicated apparatus1 and1 in order to comprehend the significance of these differences1 we must look a little more closely into the materials of which the teeth are constructed and the manner in which those materials are combined4 ,in all primitive mammals and in many of the higher and more advanced ones 7including ,man7 a tooth is composed of the crown1 or portion which is exposed above the gum1 and the roots1 one or more in number1 by means of which the tooth is firmly inserted in the jaw-bone2 the roots are at least partly formed before the tooth comes into use4 ,such a tooth is said to be short or low-crowned1 or brachyodont4 ,in many plant-feeders1 such as horses1 cattle1 elephants1 beavers1 etc41 the teeth continue to grow in height for a long time and do not form roots until late in life1 or perhaps not at all4 ,such teeth are said to be long- or high-crowned1 or hypsodont1 and in very many instances the development of brachyodont into hypsodont teeth may be followed through every step of the change4 ,the advantage of the change is obvious in lengthening the animal's life1 especially in those which feed upon abrasive substances1 like grass1 for the growth of the teeth long continues to make up for the loss through wear4 ,serious trouble has often been caused for captive elephants by giving them too soft food1 so that the growth of the teeth is not properly balanced by abrasion4 ,still another category of teeth is the rootless1 which are of simple form1 like those of an armadillo1 and grow throughout life1 never forming roots4 ,the chisel-like1 or scalpriform incisors of the rodents do not cease to grow while the animal lives2 they are kept of constant length by continual use1 and the arrangement of harder and softer tissue is such that the sharp edge is maintained2 through accident or malformation it sometimes happens that the upper and lower teeth fail to meet1 then the continued growth causes them to form curved hoops in the mouth1 locking the jaws and bringing death by starvation to the unfortunate animal4 ,illustration3 ,,fig4 #df4--;,dentition of ,beaver 7,castor canadensis74 m4 #c1 last molar4 p4 #d1 last premolar4 i41 scalpriform incisors2 enamel face black1 dentine in vertical lines4 ,the typical mammalian tooth is composed of three kinds of tissue1 all differing in structure and hardness and called respectively 7#a7 dentine1 7#b7 enamel1 7#c7 cement4 7#a7 ,the dentine1 or ivory1 is the indispensable tissue of the tooth2 the other kinds may be absent1 but never the dentine4 ,chemically1 it is like bone1 but the microscope shows that its structure is quite different from that of true bone1 being composed of an immense number of fine tubules1 which radiate from the 8pulp-cavity10 or chamber which contains the blood-vessels and nerves1 these entering the tooth through the canals of the roots4 ,the tubules of the dentine lodge excessively fine fibrill of the nerve and that is why the cutting into a live tooth is so painful an operation4 7#b7 ,the enamel1 which is the hardest of all animal tissues1 has a polished and shining appearance and is arranged in a mosaic of microscopic prisms1 closely packed together1 which in most mammals are solid1 but in the marsupials1 with some exceptions1 are tubular4 ,the enamel normally covers the entire crown of the tooth1 but does not extend upon the roots1 where its superior hardness would be of no advantage4 ,in several instances1 always as a secondary specialization1 the enamel does not cover the whole crown1 but is arranged in vertical bands1 it may be on one side only1 or at intervals around the tooth4 ,the scalpriform incisors of the rodents1 already alluded to1 have the enamel band on the front face of the tooth2 the softer dentine behind wears away more rapidly1 keeping the cutting surface bevelled1 like the edge of a chisel1 while the hard enamel forms the sharp edge4 ,in some instances the enamel is absent altogether and the teeth are composed entirely of dentine1 as in the elephant tusk4 ,in all the ,edentata1 such as sloths and armadillos1 both living and extinct1 that have any teeth at all1 the teeth have no enamel1 but in some of the fossil forms the place of the missing enamel is taken by a harder dentine and thus the effect of differential hardness is secured4 ,illustration3 ,,fig4 #dg4--,section through a lower molar of the ,indian ,elephant 7,elephas maximus74 ,enamel1 heavy black2 dentine1 white2 cement1 horizontal lines4 7#c7 ,the cement is simply bone1 both chemically and in microscopic structure2 it is not quite so hard as dentine1 but it is less affected by the fluids of the mouth and the juices of the food4 ,in the brachyodont or low-crowned tooth1 such as a human molar1 the cement merely forms a sheath over the roots and does not appear upon the crown1 but in many hypsodont teeth1 those of horses and elephants1 for example1 the cement completely encases the entire tooth in a thick layer1 filling up all the depressions and irregularities of the enamel surface and making a freshly erupted and unworn tooth look like a shapeless lump4 ,when the cement and the enamel covering are partially worn through1 the masticating surface is made up of three distinct substances1 each having a different degree of hardness and thus1 through unequal wear1 the grinding surface is always kept rough and therefore efficient4 ,not all hypsodont teeth have the cement covering1 but in such teeth the differing degrees of hardness of enamel and dentine suffice to keep a rough surface1 though not so effectively4 ,,chapter ,v ,,the ,,geographical ,,development ,,of ,,the ,,americas ,,in ,,cenozoic ,,times ,i4 ,,tertiary ,,period ,in the interior regions of western ,north ,america the transition from the ,mesozoic to the ,cenozoic was so gradual that there is great difficulty in drawing the line between them and therefore1 as might be expected1 there is much difference of opinion as to just where that line should be drawn4 ,from one point of view1 the matter is of no great consequence2 but from another1 it is of the utmost importance1 for1 unless the events in different continents can be approximately synchronized1 it will often prove a hopeless undertaking to trace the course of migration of the various mammalian groups and determine their place of origin and primary home4 ,until a definitive answer can be given to the question as to when the ,cenozoic era began1 many significant points must be left in doubt1 and much remains to be done in the geology of the ,far ,west before that definitive solution can be reached4 #a4 ,paleocene ,epoch ,so far as ,north ,america is concerned1 the best available evidence points to the conclusion that we should regard the ,fort ,union1 ,puerco and ,torrejon as the most ancient of the ,cenozoic formations 7see ,table1 p4 #ag71 though retaining so many features of ,mesozoic life that a separate division of the ,tertiary1 the ,paleocene epoch1 is made for them4 ,such a separation is not the common practice in this country1 where it is more usual to employ the terms 8,lowest0 or 8,basal0 ,eocene4 ,in my judgment1 however1 the balance of advantage is in favour of giving to this so-called ,basal ,eocene a rank equivalent to that of the four other universally recognized and admitted epochs of the ,tertiary period4 ,no marine rocks of ,paleocene date have yet been found in ,north ,america1 which indicates that the continent was at least as extensive as it is now4 ,the very scanty development of deposits representing this epoch in ,europe renders the comparison with the fossils of the ,old ,world unsatisfactory and hence leads to uncertainty1 when it is attempted to determine the land-connections of the time4 ,during the ,mesozoic era the shallow ,bering ,sea had repeatedly been elevated into a land joining ,north ,america with ,asia and had as often been depressed1 so as to separate the continents and allow the waters of the ,arctic ,ocean to mingle with those of the ,pacific4 ,a like alternation of junction and separation went on during the ,tertiary and ,quaternary periods and1 by a comparison of the fossil mammals of ,europe and ,america for any particular division of geological time1 it is almost always feasible to say whether the two continents were connected1 or altogether separated4 ,this statement does not imply that the proportion of common elements in the two faunas during epochs of continental connection was a constant one at all times1 for that was by no means true4 ,mere land-connections or separations are not the only factors which limit the spread of terrestrial animals2 if they were1 the community of forms between ,north and ,south ,america would be much greater than it actually is4 ,climatic barriers are of almost equal importance in determining animal distribution1 and changes of climate may greatly alter the conditions of migration between connected continents4 ,as the connections between ,north ,america and the ,old ,world were probably in high latitudes1 where the seas are narrow1 changes of climate produced a greater effect upon migration than they could have done had the land-bridges been in the tropical or warm temperate zones4 ,that these vicissitudes of climate really did occur and are not mere guesses to bolster up a tottering hypothesis1 there is abundant evidence to prove4 ,in the ,paleocene1 or most ancient epoch of the ,tertiary period1 the geographical condition of ,north ,america was approximately as follows3 ,the continent had attained nearly its modern outlines and on the ,atlantic and ,pacific coasts probably extended farther seaward than it does to-day4 ,florida1 however1 and perhaps a narrow strip of the northern ,gulf coast were still submerged1 the ,gulf of ,mexico opening broadly into the ,atlantic4 ,it is very probable that the continent was connected with the ,old ,world by a land occupying the site of ,bering ,sea and perhaps also by way of ,greenland and the ,north ,atlantic2 and there is some evidence1 though not altogether convincing1 that it was also joined to ,south ,america4 ,the great mountain ranges were largely what they now are1 though subsequent upheavals greatly modified the ,rocky ,mountains1 ,sierra ,nevada and the ranges of the ,pacific coast1 while the lofty ,st4 ,elias ,alps of ,alaska were not in existence4 ,the region of high plateaus1 between the ,rockies and the ,sierras1 was much less elevated than it is now4 ,the ,appalachians1 which were of far more ancient date than the western ranges1 had been worn down by ages of weathering and stream-erosion into a low-lying1 almost featureless plain1 with some scattered peaks rising from it here and there1 of which the mountains of western ,north ,carolina were the highest4 ,in general1 it may be said that while the average height of the continent above the sea-level may have been as great or greater than at present1 yet the inequalities of surface appear to have been less marked1 and both along the ,atlantic coast and in the interior were vast stretches of plains4 ,the ,paleocene formations of the western interior are of non-marine or continental origin4 ,in northwestern ,new ,mexico is the typical area of the ,puerco and ,torrejon1 a series of beds #hjj to #ajjj feet in thickness and for the most part quite barren of fossils1 but there are two horizons1 one near the top and the other near the bottom of the series1 which have yielded a very considerable number of fossil mammals1 and of these the lower is the ,puerco1 the upper the ,torrejon4 ,the ,fort ,union is quite different in character and is composed of great areas of sandstone and clay rocks1 with a maximum thickness of #bjjj feet1 in eastern ,wyoming1 ,south ,dakota1 ,montana and the adjoining parts of ,canada4 ,the modes of formation of these beds have not yet been fully determined2 that they may have been partly laid down in shallow lakes is indicated by the masses of fresh-water shells in certain localities4 ,in others are preserved multitudes of leaves1 which have given a very full conception of the plants of the time1 and great swamps and bogs have left the traces of their presence in beds of lignite1 or imperfectly formed coal4 ,deposits made on the flood-plains of rivers and wind accumulations are probably also represented4 8,vast stretches of subtropical and more hardy trees were interspersed with swamps where the vegetation was rank and accumulated rapidly enough to form great beds of lignite4 ,here were bogs in which bog iron was formed4 ,amid the glades of these forests there wandered swamp turtles1 alligators1 and large lizards of the characteristic genus ,champsosaurus0 7,osborn1 p4 #ajj74 ,fort ,union mammals are relatively rare and most of those that have been found are very fragmentary2 they are amply sufficient1 however1 to demonstrate the ,paleocene date of the beds and to make it probable that they include both the ,puerco and the ,torrejon faunas4 ,the climate1 as shown by the plants1 was much milder and more uniform than that of the ,recent epoch1 though some indication of climatic zones may already be noted4 ,the vegetation was essentially modern in character2 nearly all our modern types of forest-trees1 such as willows1 poplars1 sycamores1 oaks1 elms1 maples1 walnuts and many others1 were abundantly represented in the vast forests which would seem to have covered nearly the entire continent from ocean to ocean and extended north into ,alaska and ,greenland1 where no such vegetation is possible under present conditions4 ,numerous conifers were mingled with the deciduous trees1 but we do not find exclusively coniferous forests4 ,palms1 though not extending into ,greenland1 flourished magnificently far to the north of their present range4 ,on the other hand1 the ,paleocene flora of ,england points to a merely temperate climate1 while that of the succeeding ,eocene was subtropical4 ,south ,america4--,nothing is definitely known concerning the condition of ,central ,america and the ,west ,indies and very little as to ,south ,america4 ,as no marine rocks of ,paleocene date have been found in any of these regions1 it may be inferred that all the existing land areas were then above the sea1 and there is some evidence that ,south ,america was much more extended in certain directions than now4 ,from the character and distribution of modern plants1 fresh-water fishes1 land and fresh-water shells1 there is strong reason to believe that in late ,mesozoic times a land-bridge connected ,brazil with equatorial ,africa and this connection may have continued into the ,paleocene1 though it is only fair to observe that some highly competent authorities deny the reality of this bridge4 ,there is also evidence1 though incomplete1 of a connection between ,south ,america and ,australia by way of the ,antarctic continent1 and it is clear that that polar region could not have had the rigorous climate of the present time4 ,in the upper part of the ,cretaceous1 the last of the ,mesozoic periods1 there was a possibility of migration1 however indirect1 between every continent and every other1 for the huge land reptiles called ,dinosaurs have been found in the non-marine ,cretaceous rocks of every continent1 which could not have been the case1 had any of the great land areas been isolated4 ,there is no known reason to assume that the land-bridges were essentially different in the ,paleocene4 #b4 ,eocene ,epoch ,north ,america4--,the ,eocene witnessed quite extensive geographical changes1 though but little is known of it in ,central or ,south ,america1 or the ,west ,indies4 ,along the ,atlantic and ,gulf coasts of the ,united ,states there was an extensive submergence of the coastal plain1 the sea covering the southern half of ,new ,jersey and extending thence to the southwestward in an ever broadening band1 through the ,south ,atlantic and ,gulf states4 ,northern ,florida was under water and the ,gulf extended as a narrow sound1 known as the 8,mississippi ,embayment10 up the valley of that river to southern ,illinois and westward into ,texas4 ,the ,embayment was present in the ,cretaceous and again in the ,eocene1 but it is not known whether it persisted through the ,paleocene2 probably it did not1 as the whole ,atlantic coast region appears to have stood at a higher level then than now4 ,while the condition of ,mexico and ,central ,america during the ,eocene is not known in any save the vaguest manner1 it is evident that there was then a broad communication between the ,atlantic and the ,pacific1 completely severing ,north and ,south ,america1 though the place of this transverse sea has not been fixed4 ,on the ,pacific side1 a long1 narrow arm of the sea occupied what is now the great valley of ,california1 extending north into ,oregon and ,washington4 ,it will be noted that in ,north ,america the ,eocene sea was almost confined to the neighbourhood of the present coast-lines1 nowhere penetrating very far inland1 except in the ,mississippi ,embayment1 and thus differing widely from the condition of ,europe at that epoch1 where much of what is now land was submerged4 ,the greatly expanded ,mediterranean covered most of southern ,europe1 where the great mountain ranges1 the ,pyrenees1 ,alps1 etc41 had not yet been formed4 ,very important1 from the point of view of ,american geography1 is the fact that ,europe was completely separated from ,asia by a narrow strait or sea1 which ran down the eastern side of the ,ural ,mountains from the ,arctic ,ocean and joined the enlarged ,mediterranean4 ,during the existence of this ,ural ,sea any land connection of ,north ,america with ,europe must necessarily have been by means of a ,north ,atlantic bridge1 or by one across the ,arctic ,sea1 since communication with ,asia by way of ,alaska would not have reached eastern ,europe4 ,illustration3 ,,fig4 #dh4--,map of ,north ,america during the ,eocene epoch4 ,the present limits of the continent are shown in outline2 white areas land2 horizontal lines sea2 dotted areas non-marine deposits2 black circles with white dots active volcanoes4 7,after ,schuchert47 ,any such general statement of geographical conditions during the ,eocene as the foregoing sketch1 cannot but be to some extent misleading1 because it brings together1 as contemporary1 arrangements which were1 in some cases at least1 separated by considerable intervals of time and which were subject to continual change4 ,along nearly all coasts the position of the sea was quite different in the latter part of the epoch from what it had been in the earlier portion4 ,on the north side of the ,gulf of ,mexico1 for example1 the sea retreated from time to time1 and the successive divisions of the ,eocene rocks are so arranged that the later ones are farther to the south4 ,limitations of space1 however1 forbid the attempt to follow out these minor changes4 ,illustration3 ,,fig4 #di4--;,bad ,lands of the lower ,eocene4 ,wasatch stage4 ,big ,horn ,basin1 ,wyo4 7,photograph by ,sinclair47 ,in the western interior are found extensive non-marine or continental deposits of ,eocene date1 which must be considered more in detail1 because of the highly important bearing which they have upon mammalian history4 ,with the exception of a few small areas in ,colorado1 these deposits are all situated in the plateau region west of the ,rocky ,mountains1 and were made of the dbris of older rocks washed down by rain and rivers and deposited in broad basins4 ,some of them are the sediments of shallow or temporary lakes1 and one series1 at least1 is made up of volcanic ash and dust showered upon the land1 or into water of no great depth4 ,the oldest of these ,eocene stages1 known as the ,wasatch 7see ,table1 p4 #ag7 covers a very large region1 though in a discontinuous manner2 the principal area begins in ,new ,mexico1 where it lies over the ,torrejon1 of the ,paleocene1 and extends far to the north through western ,colorado and eastern ,utah to the ,uinta ,mountains1 around the eastern end of which it passes in a narrow band and then expands again over southwestern ,wyoming4 ,a second area is in the ,big ,horn ,basin of northwestern ,wyoming and southern ,montana1 and probably two small areas in southern ,colorado are of the same date4 ,the ,wasatch beds are richly fossiliferous and have yielded a most interesting and important series of mammals1 which were far more advanced than those of the ,paleocene2 and1 at first sight1 the student is tempted to believe that they must be of very much later date4 ,a more critical examination shows that this appearance of a great lapse of time between the ,paleocene and the ,wasatch is deceptive2 the more advanced and characteristic of the ,wasatch mammals were obviously not the descendants of ancestors in the ,north ,american ,paleocene1 but were altogether newcomers to this continent1 immigrants from some region which cannot yet be identified4 ,on the other hand1 a considerable number of the old1 indigenous types still persisted1 and these1 when compared with their ,paleocene ancestors1 are found not to have changed so much as to require a very great length of time1 geologically speaking1 for the degree of development involved4 ,this is the earliest recorded one of the great waves of mammalian migration which invaded ,north ,america down almost to our own time4 ,the same wave of migration extended to ,europe1 and that there was a broad and easy way of communication between that continent and ,north ,america is plain1 for the similarity between the ,wasatch mammals and those of the corresponding formation in ,france1 the ,sparnacian1 is remarkably close4 ,at no subsequent time were the mammalian faunas of ,north ,america and ,europe so nearly identical as during the ,wasatch-,sparnacian age1 which is especially remarkable when the discrepancy is noted between the vast stretches of the ,wasatch 7#aej1jjj square miles7 and the very limited areas in ,france4 ,if1 as is probable1 the ,ural ,sea was in existence at that time1 the land-connection with ,europe must have been across the ,north ,atlantic1 most likely from ,greenland eastward4 ,at the present time a land-bridge in such high latitudes would be of little service in bringing about a similarity of mammals in the two continents1 for the severity of the ,arctic climate would be as effective a barrier against the intermigration of all save the ,arctic mammals as the ocean itself2 but in the mild and genial ,eocene climate the latitude of the bridge was of small consequence4 ,the second of the ,eocene stages1 the ,wind ,river--,green ,river1 is found in two very different phases4 ,the ,wind ,river phase occupies the basin of that stream1 north of the ,wind ,river ,mountains in central ,wyoming1 and in the ,big ,horn ,basin of the same state it very extensively overlies the ,wasatch1 and in this phase the sediments are very like those of the latter1 flood-plain and wind accumulations4 ,a widely distant area of this stage occurs in the ,huerfano ,caon in ,colorado4 ,the ,wind ,river beds contain numerous mammals which were clearly sequential to those of the ,wasatch1 of which they were the more or less modified descendants4 ,with two possible exceptions1 there were no new immigrants and the connection with the ,old ,world may have been already severed1 as it assuredly was in the succeeding age1 the ,bridger1 though divergent development had not yet had time to produce the very striking differences in the mammals of ,north ,america from those of ,europe1 which characterized the ,bridger4 ,the ,green ,river phase is a thick body of finely laminated 8paper shales10 which seem to have been deposited in a very shallow lake and occupy some #ejjj square miles of the ,green ,river valley in southern ,wyoming and northern ,utah1 where they overlie the ,wasatch1 just as do the ,wind ,river beds in the ,big ,horn ,basin4 ,these fine-grained and thinly laminated shales have preserved1 often in beautiful perfection1 countless remains of plants1 insects and fishes1 but no traces of mammals1 other than footprints1 have been found4 ,the third of the ,eocene stages of the interior is the ,bridger of southern ,wyoming and northeastern ,utah1 where it lies upon the ,green ,river shales1 but overlaps these shales both eastward and westward1 extending out upon the ,wasatch4 ,the ,bridger beds are largely made up of volcanic ash and dust deposited partly upon the land and partly in shallow or temporary lakes4 ,the frequency with which the remains of fishes1 crocodiles and fresh-water shells are found indicates deposition in water1 and the large crystals of gypsum which are abundant in certain localities show that the water became salt1 at least occasionally4 ,from the immense mass of volcanic dbris1 it is evident that volcanic activity broke out at this time on a much greater scale than had been known in that region since the ,cretaceous period4 ,two different horizons1 or substages1 are distinguishable in the ,bridger1 lower and upper1 each of which has its distinct mammalian fauna1 though the two are very closely allied4 ,their difference from the contemporary mammals of ,europe is very great1 hardly any genera being common to the two continents4 ,so striking a difference indubitably points to a severance of the land-connection1 a severance which1 as was shown above1 probably took place during the ,wind ,river stage1 for its effects would not be immediately apparent2 time would be required for the operation of divergent evolution1 the fauna of each continent developing along its own lines1 to make itself so strongly felt4 ,had the connection never been renewed1 ,north ,america1 on the one hand1 and ,eurasia on the other1 would to-day be utterly different from the zological point of view1 instead of containing1 as they do1 a great many identical or closely similar animals of all classes1 a likeness due to subsequent migrations4 ,the fourth and last of the stages referred to the ,eocene is the ,uinta1 the geological position of which is the subject of much debate2 almost as good reasons can be brought forward for placing it in the ,oligocene as in the ,eocene1 so nearly is it on the boundary line between those two epochs4 ,the ,uinta is found in the ,green ,river valley of northeastern ,utah and northwestern ,colorado1 where it lies upon the upper ,bridger and is the latest of the important ,tertiary formations to be found in the plateau region west of the ,rocky ,mountains4 ,it is probable that the separation of ,north ,america from the ,old ,world still continued1 for1 as a whole1 the ,uinta fauna is totally different from that of the upper ,eocene of ,europe4 ,there were1 however1 a few doubtful forms1 which may prove to be the outposts of a renewed invasion4 ,the ,eocene climate was decidedly warmer than the present one1 and subtropical conditions extended over the whole ,united ,states and perhaps far into ,canada4 ,on the other hand1 signs of increasing aridity in the western part of the continent are not wanting1 and that must have resulted in a great shrinkage of the forests and increase of the open plains4 ,the vegetation was essentially the same as in the ,paleocene1 when it had already attained a modern character1 the differences from the present being chiefly in regard to geographical distribution4 ,large palms were then flourishing in ,wyoming and ,idaho1 and another indication of a warm climate is furnished by the large crocodiles which abounded in all of the ,eocene stages4 ,so far as ,north ,america was concerned1 the ,eocene epoch was brought to a close by extensive movements of the earth's crust1 which more or less affected the entire continent and were registered both on the sea-coasts and in the mountain ranges of the interior4 ,upheaval added a narrow belt of land along the ,atlantic and ,gulf coasts and the ,mississippi ,embayment was nearly closed4 ,on the ,pacific side the sea withdrew from the great valley of ,california and ,oregon1 and in the interior the plateau region was elevated by a great disturbance1 which also increased the height of the western mountains4 ,our knowledge of ,eocene land-mammals in ,north ,america is almost wholly derived from the formations of the western ,united ,states1 but it may be inferred from the uniform climatic conditions that there were no very great geographical differences among the animals4 ,this inference is confirmed by the discovery of a ,bridger genus1 very fragmentary but identifiable1 in the marine ,eocene of ,new ,jersey4 ,south ,america4--,no ,eocene rocks1 marine or continental1 are known in the ,west ,indies or ,central ,america1 but the latter region has been so imperfectly explored that no great importance can be attached to this fact4 ,north and ,south ,america were separated completely1 as is proved by the entire dissimilarity of their mammalian faunas1 but the position of the transverse sea or strait cannot be determined4 ,there is much reason to believe that the ,greater ,antilles were connected into a single large land1 which has been called 8,antillia0 and may have been joined to the mainland of ,central ,america4 ,certain marine rocks in ,patagonia and ,chili have been referred to the ,eocene by ,south ,american geologists1 but the reference is almost certainly erroneous1 the rocks in question being much more probably ,miocene4 ,the ,andes1 probably throughout their length and certainly in their southern half1 stood at a much lower level than they do now1 and1 no doubt1 were rising1 either slowly and steadily1 or periodically and more rapidly1 throughout the whole ,tertiary period4 ,at all events1 their present height in the south is due to movements in the ,pliocene or later4 ,continental deposits of ,eocene date have been discovered only in northern ,patagonia 7,casa ,mayor7 where they occupy depressions in the worn and eroded surfaces of the ,cretaceous rocks2 the mode of their formation has not been carefully studied4 ,there is great uncertainty as to the status of the land-bridge which1 it is believed1 in the ,cretaceous period connected ,south ,america with ,africa4 ,some of the evidence goes to show that the connection persisted throughout the ,eocene epoch1 but the testimony is that of fragmentary and therefore imperfectly understood fossils and is far from being unequivocal4 ,the connection with ,antarctica probably continued4 #c4 ,oligocene ,epoch ,north ,america4--,the ,oligocene1 or third of the ,tertiary epochs1 was a time of great significance in the history of the ,american mammals and of great geographical changes in the ,west ,indian and ,central ,american regions1 but in ,north ,america proper the changes were not so widespread4 ,on the ,atlantic coast the marine ,oligocene is but scantily displayed except in the ,florida peninsula1 where it is found in a thickness of some #bjjj feet1 but it is well developed along the north shore of the ,gulf of ,mexico1 where the coast-line followed that of the ,eocene1 only a little farther to the south1 marking the retreat of the sea at the end of the ,eocene4 ,the ,gulf ,stream entered the ,atlantic over the site of northern ,florida and flowed northward nearer the coast than it does to-day1 in consequence of which warm-water conditions extended far to the north and ,west ,indian shells flourished on the ,new ,jersey coast4 ,in the middle ,oligocene part of northern ,florida was elevated into an island and the water over much of the remainder of the peninsula became shallower1 but this did not greatly alter the course of the ,gulf ,stream4 ,the ,pacific encroached upon the western shore of ,oregon and ,british ,columbia and very extensively upon that of ,alaska1 where strata no less than #aj1jjj feet thick are assigned to this epoch4 ,in the western interior ,oligocene formations are among the most important and widely spread of the continental ,tertiaries and are divisible into two principal stages and each of these again into three substages4 ,of these1 the older or ,white ,river stage covers a vast region in northeastern ,colorado1 western ,nebraska1 eastern ,wyoming and southern ,south ,dakota1 with separate areas in the ,black ,hills1 ,north ,dakota and the ,northwest ,territory of ,canada4 ,the deposits are believed to be chiefly of fluviatile origin1 and many of the ancient stream-channels1 some of great size1 may still be traced1 filled with the consolidated sands and gravels of the old rivers4 ,the country was very flat and the divides between the streams very low1 so that in seasons of flood great regions were converted into shallow1 temporary lakes1 in which were deposited the finer silt and mud1 but were dry for most of the year4 ,the volcanic activity which had gone on so impressively in the ,bridger ,eocene was renewed in ,white ,river times1 as is proved by thick beds of pure volcanic ash1 which must have been carried long distances by the wind1 for they occur far from any volcanic vent4 ,illustration3 ,,fig4 #ej4--,map of ,north ,america in the upper ,oligocene4 ,explanation as in ,fig4 #dh4 7,after ,schuchert47 ,the ,white ,river fauna is more completely known than that of any other ,tertiary formation of this continent4 ,the first discovery of these fossils was made more than #gj years ago and since then oft-repeated expeditions have brought to light an astonishing number and variety of mammals4 ,not only are these beds remarkable for the immense quantity of material which they have yielded1 but also for its completeness and beauty of preservation1 a most unusual number of skeletons having been obtained4 ,the mammals demonstrate that the land-connection with the ,old ,world had been re-established1 for many ,european genera1 which could not have been derived from an ,american ancestry1 are found in the ,white ,river beds4 ,at the same time1 there was no such proportion of forms common to both continents as there had been in the ,wasatch-,sparnacian stage of the lower ,eocene1 each having many genera and even families which did not extend their range into the other4 ,the reason for this remarkable and1 at first sight1 inexplicable difference between the lower ,eocene and the lower ,oligocene is probably to be found in climatic changes1 in consequence of which relatively fewer genera were able to take advantage of the reopened connection1 which lay far to the north4 ,the ,white ,river mammals1 like those of the ,recent epoch1 are thus divisible into two groups or elements1 one set indigenous and descended from ancestors which are found in the ,american ,eocene1 and the other composed of late immigrants from the ,old ,world4 ,migrants from ,north ,america likewise made their way to ,europe4 ,the upper continental ,oligocene of the interior has received the peculiar appellation of the ,john ,day1 from the river of that name in eastern ,oregon1 a large part of which was buried to a depth of #cjjj or #djjj feet in stratified volcanic ash and tuff4 ,this great mass of finely divided volcanic material was derived from the craters of the ,cascade ,mountains to the westward2 a long-continued series of eruptions would be needed to form such thick accumulations at such a distance from the sources of supply4 ,the ,john ,day evidently succeeded the ,white ,river very closely in time1 but is marked by the disappearance of almost all the ,european migrants4 ,this fact1 together with the absence of any new immigrant genera1 is evidence that the connection had again been broken and it was not renewed until after a considerable lapse of time4 ,there are many reasons for believing that the ,oligocene climate marked the beginning of the very long and gradual process of refrigeration which culminated in the glacial conditions of the ,pleistocene epoch1 but the change was slight and probably chiefly affected the far north4 ,the climate1 however1 remained notably warmer than the present one of the same extra-tropical latitudes1 as is abundantly proved by the fossils4 ,the ,atlantic coast1 as noted above1 was bathed in warm waters1 the plants of the ,alaskan ,oligocene point to temperate conditions and the vegetation of ,europe was subtropical1 palms growing in the north of ,germany4 ,the change which was distinctly to be noted in the ,great ,plains region of ,north ,america was probably due rather to the elevation and increased altitude of the western interior than to general climatic alteration4 ,crocodiles are very rare indeed in the ,white ,river beds and those that have been found all belong to dwarf species1 while none are known from the ,john ,day4 ,unfortunately1 hardly anything has been ascertained concerning the ,oligocene vegetation of the region1 but the reptiles indicate diminished warmth4 ,south ,america4--,marine ,oligocene strata have great extent around the ,gulf of ,mexico and the ,caribbean ,sea1 and the distribution of these shows that ,antillia was broken up by great submergences1 the islands of the ,greater ,antilles being much smaller than they are to-day4 ,the greater part of ,central ,america and the ,isthmus were under water1 a broad sea1 broken only by scattered islands1 separating ,north and ,south ,america4 ,very little is known of the ,oligocene in the latter continent save a non-marine formation in northern ,patagonia1 the ,deseado stage 7or ,pyrotherium ,beds71 which1 like the ,eocene of the same region1 occupies depressions in the worn and irregular surface of the ,cretaceous rocks4 ,the attribution of the ,deseado to the ,oligocene is open to some doubt1 because of the entire absence in its mammalian fauna of any elements which are also found in the northern hemisphere4 ,hence1 there are no means of direct comparison4 #d4 ,miocene ,epoch ,north ,america4--,the ,atlantic and ,gulf coasts1 which had been raised in the ,oligocene1 were again depressed1 almost restoring the ,eocene coast-line1 the chief differences being the presence of the ,florida islands and the nearly complete closing of the ,mississippi ,embayment4 ,there was a remarkable change in the marine fauna from that of ,oligocene times2 a cool current flowed southward along the coast and entered the ,gulf of ,mexico through the strait between the ,florida island and the mainland1 bringing the northern animals with it and driving out the tropical forms4 ,this complete faunal change1 which might fairly be called a revolution1 was the most sudden and striking in the ,tertiary history of the continent4 ,on the ,pacific coast also there was a depression1 which caused a renewed transgression of the sea4 ,the ,coast ,range formed a chain of reefs and islands in the ,miocene sea1 which again filled the great valley of ,california1 except in the northern part of what is now the ,sacramento ,valley1 where there was an accumulation of continental deposits4 ,the immense thickness 7#ejjj to #gjjj feet7 of the ,california ,miocene is largely made up of volcanic material1 which testifies to the great activity of the vents4 ,in the ,sierras1 the height of which was increased in the upper ,miocene1 there was also a great display of vulcanism1 recorded in the lava-flows and tuffs of the time4 ,in the region of ,lower ,california and northwestern ,mexico considerable changes of the coast-line took place during the ,miocene2 in the earlier half of the epoch the ,gulf of ,california was much shorter and narrower than it is to-day and the peninsula was broadly united with the mainland to the east as well as to the north4 ,a wide submergence marked the upper ,miocene1 reducing the peninsula to a long1 narrow island and enlarging the gulf considerably beyond its present limits1 flooding an extensive area in northwestern ,mexico and sending a small bay into southeastern ,california4 ,there were great disturbances in the course of the epoch1 for in the ,santa ,cruz ,mountains near ,san ,francisco the lower ,miocene strata were crumpled into folds1 before those of the upper ,miocene were deposited upon them4 ,british ,columbia1 ,washington and ,oregon were invaded by the sea1 which extended up the valley of the ,columbia ,river and its southern tributary1 the ,willamette1 though here the beds are far thinner than those of ,california4 ,much of ,alaska1 both on the north and west coasts and in the valley of the ,yukon1 was submerged1 and the land-connection with ,asia appears to have been broken4 ,this is made probable not only by the submergence of the ,alaskan coast1 but also by the fact that the marine animals of the ,california coasts and shoal waters1 which could not migrate across the ocean1 were quite unlike the contemporary forms of the eastern ,asiatic shore1 which would hardly have been the case1 had a continuous coast-line united the two continents4 ,on the other hand1 there was a renewed connection with ,europe1 as is shown by the appearance of ,old ,world land-mammals1 beginning scantily in the lower and becoming numerous in the middle ,miocene4 ,this connection1 it will be remembered1 had been interrupted during the upper ,oligocene4 ,many students of the problem have maintained that the land-bridge was by way of the ,west ,indies and the ,mediterranean lands1 but such a bridge would not account for the facts of mammalian distribution1 which would seem to require its location in the far north4 ,illustration3 ,,fig4 #ea4--,map of ,north ,america in the upper ,miocene4 ,explanation as in ,fig4 #dh4 7,modified from ,schuchert47 ,several distinct lines of evidence go to prove that the junction of the ,americas dates from the ,miocene1 possibly from the beginning of it4 ,the absence of ,atlantic species from the ,pacific ,miocene is an indication that the passage from ocean to ocean had been closed1 and this is confirmed by the geology of the ,central ,american and ,isthmian region4 ,in the middle ,miocene of ,oregon and ,nebraska have been found remains1 which are unfortunately too incomplete for altogether convincing identification1 but which can be interpreted only as belonging to the extinct and most characteristically ,south ,american group of edentates1 the ground-sloths or ,gravigrada2 if this reference is correct1 the fact of the junction cannot be questioned4 ,continental deposits of ,miocene date1 chiefly accumulations made by rivers and the wind1 cover vast areas of the western interior1 though but rarely to any considerable depth4 ,these have been divided into several stages and have received various names2 the lower ,miocene1 known as the ,arikaree1 ,harrison or ,rosebud1 overlies the ,white ,river in ,south ,dakota1 western ,nebraska and eastern ,wyoming1 with smaller areas in ,montana and ,colorado4 ,in the deposits of this stage there are no mammals of indisputably ,old ,world type1 though a few which ,i consider to be such are a probable indication of renewed connection with ,europe4 ,the middle ,miocene is found typically in central ,montana1 where it is called the ,deep ,river 7or ,smith ,river7 stage1 but occurs also in numerous small1 scattered and widely separated areas in ,oregon1 ,wyoming1 ,colorado and ,texas1 with local names in these different states4 ,it is most likely that these middle ,miocene formations are not strictly contemporaneous in the geological sense1 but rather form a closely connected and successive series4 ,the mammals of the ,deep ,river stage leave no doubt that the way of migration from the ,old ,world was again open4 ,the ,loup ,fork1 or upper ,miocene1 itself susceptible of further subdivision1 is by far the most extensive of the ,miocene formations and covers much of the ,great ,plains region1 in separate areas1 from ,south ,dakota far into ,mexico4 ,perhaps also referable to the upper ,miocene is a small1 but very interesting formation1 the ,florissant1 which is in the ,south ,park of ,colorado2 it was made by very fine volcanic material showered into a small and shallow lake4 ,the finely laminated papery shales of the ,florissant have preserved countless plants and insects and many fishes1 and these throw very welcome light upon the vegetation and climatic conditions of the epoch and afford an interesting contrast to the fauna and flora of the ,green ,river shales of the lower or middle ,eocene4 ,that the ,florissant shales are ,miocene1 no one questions1 but their isolated position and the fact that they have yielded no mammals make it somewhat doubtful whether they belong in the middle or later part of the epoch4 ,in the western portion of the continent vulcanism was displayed on a grand scale during the ,miocene4 ,mention has already been made of the quantity of volcanic material in the marine ,miocene of ,california and also in the lavas and tuffs of the ,sierras4 ,the magnificent cones1 such as ,mts4 ,hood and ,tacoma1 which are the glory of the ,cascades1 are believed to date from this time4 ,in ,idaho and eastern ,oregon and ,washington are the immense lava-fields of the ,columbia ,river1 which are1 partly at least1 of ,miocene date and were chiefly extruded through great fissures1 the lava flooding the valleys and plains in a fiery sea of molten rock4 ,in ,oregon these lavas rest upon the upper ,oligocene 7,john ,day stage7 and middle ,miocene beds are deposited upon them1 which fixes their date sufficiently4 ,in the ,yellowstone ,park was piled up a huge mass of volcanic products1 lava-flows and beds of ash and tuff1 to a thickness of several thousand feet4 ,the ash-beds have preserved the petrified forests1 with their tree-trunks still standing one above another2 one locality in the ,park shows seven such forests1 each one killed and buried by a great discharge of ash and then a new forest established and growing upon the surface of the accumulation4 ,in the tuffs are leaf-impressions which permit identification of the plants4 ,in the latter part of the ,miocene and at its close there were important crustal movements1 which affected all the ,pacific coast mountain ranges1 though this epoch was no such time of mountain making in ,america as it was in the ,old ,world4 ,the principal elevation of the ,coast ,range in ,california and ,oregon was due to these movements1 and the ,sierras and the plateaus of ,utah and ,arizona were increased in height4 ,on the ,atlantic side the ,florida island was joined to the mainland and thus the present shape of the continent was almost exactly gained4 ,the ,miocene climate of ,north ,america1 as indicated by the plants of ,florissant1 the ,yellowstone ,park and ,oregon1 was distinctly milder than at present1 a southern vegetation of warm-temperate character extending to ,montana and perhaps much farther north1 but it was not so warm as it had been in the ,eocene1 and palms are not found in any of the localities mentioned1 nor do crocodiles occur in any of the northern ,miocene formations4 ,in ,europe the climate of the early ,miocene was considerably warmer than in ,north ,america1 the vegetation of central and western ,europe being very much like that of modern ,india4 ,this difference between the two sides of the ,atlantic was probably due1 in large part1 to the manner in which ,europe was broken and intersected by arms and gulfs of the warm southern sea4 ,in the latter half of the epoch1 however1 the climate became colder1 the subtropical flora giving way to a distinctly temperate one4 ,south ,america4--,in ,central ,america1 where marine ,oligocene beds are of great extent1 no ,miocene is known1 and on the ,isthmus ,oligocene is the latest marine formation1 except a narrow fringe of ,pleistocene on the ,caribbean coast4 ,these facts and others already cited lead to the conclusion that in the ,miocene the connection of the ,americas was complete and that the ,isthmus was considerably broader than at present1 extending nearly to ,jamaica4 ,the condition of the ,greater ,antilles is but vaguely understood1 but they were involved in the general elevation of the ,caribbean region and were at least as large as they are now and may have been considerably larger1 and ,cuba was perhaps joined to ,central ,america1 as ,hayti probably was4 ,in ,south ,america proper nearly the whole of ,patagonia was submerged by the transgression of a shallow1 epicontinental sea1 in which were accumulated the beds of the ,patagonian stage1 containing an exceedingly rich and varied assemblage of marine fossils1 an assemblage which has very little in common with the contemporary formations of the northern hemisphere4 ,it is this lack of elements common to the northern faunas which has led to the long debate concerning the geological date of the ,patagonian formation1 the ,south ,american geologists very generally referring it to the ,eocene4 ,however1 the occurrence of genera of ,cetaceans 7whales and dolphins71 which are also found in the ,miocene of ,maryland and ,virginia1 is very strong evidence that the proper date of the ,patagonian is ,miocene4 ,a continuous coast-line1 or at least an unbroken continuity of shoal-water conditions1 seems necessary to account for the similarity of the ,patagonian fossils with those of ,new ,zealand and ,australia1 and that this connection was by way of the ,antarctic continent is indicated by the occurrence of similar fossils in the ,south ,shetland ,islands1 an ,antarctic group4 ,on the ,chilian coast the ,navidad formation1 which is believed to be approximately contemporaneous with the ,patagonian1 has so different a fauna as to point to some kind of a barrier between the ,atlantic and the ,pacific1 and this barrier1 ,dr4 von ,ihering holds1 was the land-extension from ,south ,america to ,antarctica4 ,after some oscillations of retreat and advance1 the sea withdrew from ,patagonia and the terrestrial accumulations of the ,santa ,cruz stage were formed4 ,these beds are partly composed of river-deposits1 but chiefly of more or less consolidated volcanic ash or tuff1 and have yielded a surprising number of beautifully preserved mammals4 ,no other assemblage of ,south ,american ,tertiary ,mammalia is so well known and understood as the ,santa ,cruz fauna1 and the very large number of all but complete skeletons which have been found strongly suggests that many of the animals were buried alive in the showers of volcanic ash4 ,the ,santa ,cruz fauna is completely and radically different from any of the ,north ,american assemblages1 and at that time no immigrant from the north had penetrated so far as ,patagonia4 ,in the upper ,miocene the ,andes stood at a much lower level than they do now2 fossil plants1 some of them collected at a great height in the mountains1 are the remains of a luxuriant and purely tropical flora nearly identical with the vegetation of the modern forests of ,bolivia and ,brazil4 ,such a vegetation could not exist at the altitudes where the fossils occur and these demonstrate a great elevation of the mountains since those leaves were embedded4 ,the same mild climatic conditions which prevailed in the northern hemisphere during the ,miocene must also have characterized ,patagonia1 subtropical shells extending far to the south of their present range4 ,whatever may have been true of the land-bridge connecting ,south ,america with ,africa during the early ,tertiary epochs1 it must have been submerged in the ,miocene1 otherwise there would not have been the open pathway for the ,cetacea of ,patagonia to reach the ,atlantic coast of ,north ,america and vice versa4 #e4 ,pliocene ,epoch ,north ,america4--,the ,pliocene of ,north ,america is not nearly so well displayed or so satisfactorily known as the preceding ,tertiary epochs1 and only of comparatively late years has it been recognized at all upon the ,atlantic coast4 ,the ,atlantic and ,gulf shores had very nearly their present outlines1 but with some notable differences4 ,it would seem that the northeastern portion of the continent stood at a higher level than it does now1 north ,greenland being joined with the islands of the ,arctic archipelago and ,newfoundland with ,labrador1 the ,gulf of ,st4 ,lawrence then being land4 ,from ,nova ,scotia to southern ,new ,jersey the coast-line was many miles to the east and south of its present position1 but the sea encroached here and there upon the shores of ,virginia1 the ,carolinas and ,georgia1 and southern ,florida was mostly under water1 as was also a narrow strip of the ,gulf coast from ,florida to ,texas and along the east of ,mexico4 ,on the ,pacific side of the continent the marine ,pliocene is far thicker and more important than on the east coast and in ,california is largely made up of volcanic materials4 ,quite extensive disturbances in this region had marked the close of the ,miocene1 the strata of which in the ,coast ,range had been violently compressed and folded4 ,an elevation of the land had caused the sea to withdraw from the central valley of ,california and had restored ,lower ,california to its peninsular conditions1 reducing the gulf to the narrow limits which it had had in the lower ,miocene and extending southern ,mexico to the west and south4 ,british ,columbia and southeastern ,alaska stood at higher than their present levels and the countless islands of that region were part of the mainland4 ,bering ,strait was closed1 for at least a great part of the epoch1 and1 as a continuous shore-line was thus formed and a way of migration opened1 the marine fauna of ,california and ,japan became closely similar4 ,illustration3 ,,fig4 #eb4--,map of ,north ,america during the ,pliocene epoch1 ,bering ,strait open4 ,explanation as in ,fig4 #dh4 7,modified from ,schuchert47 ,in the interior1 the ,pliocene continental formations and faunas followed so gradually upon those of the ,miocene1 that there is great doubt as to where the line between them should be drawn4 ,these interior formations are mostly of small extent and are very widely scattered1 and much remains to be learned regarding the mammals of the epoch4 ,in northern ,kansas are the ,republican ,river beds1 which are so doubtfully ,pliocene1 that they may almost equally well be called uppermost ,miocene4 ,other lower ,pliocene stages1 representing various divisions of time1 are the ,alachua of northern ,florida1 the ,snake ,creek of western ,nebraska1 the ,thousand ,creek and ,virgin ,valley of northwestern ,nevada and the ,rattlesnake of ,oregon4 ,probably middle ,pliocene is the ,blanco of northwestern ,texas1 a valley cut in the middle and lower ,miocene rocks and filled in with ,pliocene deposits4 ,possibly upper ,pliocene1 or1 it may be1 lowest ,pleistocene1 are the ,peace ,creek of southwestern ,florida and the so-called 8,loup ,river0 7not ,loup ,fork7 of western ,nebraska4 ,the volcanic activity of the ,rocky ,mountain and ,pacific coast regions1 which was so remarkable in the ,miocene1 continued into and perhaps through the ,pliocene4 ,the great outflow of light-coloured lava which built up the central plateau of the ,yellowstone ,park is referred to the ,pliocene1 and some of the enormous fissure-eruptions which formed the vast ,columbia ,river fields of black basaltic lava were probably ,pliocene1 as some were demonstrably ,miocene4 ,both of these epochs were remarkable for volcanic activity in the western part of the continent4 ,the ,pliocene climate1 as may be inferred from the plants and marine shells1 was colder than that of the ,miocene1 and refrigeration was progressive1 as is shown by the proportion of ,arctic shells in the ,pliocene beds of the east coast of ,england1 rising from #e per cent in the oldest to more than #fj per cent in the latest beds4 ,in the ,arctic regions the cold must have been severe1 at least during the latter half of the epoch1 for in the succeeding ,pleistocene we find an ,arctic fauna already fully adapted to the extreme severity of present day polar conditions and time was necessary for such an adaptation4 ,in the western interior the climate was not only colder1 but also drier than it had been in the ,miocene1 the desiccation which had begun in the latter epoch becoming progressively more and more marked4 ,south ,america4--,the ,greater ,antilles were larger than at present and ,cuba was much extended1 especially to the southeastward1 and was probably connected with the mainland1 not as one would naturally expect1 with ,yucatan1 but with ,central ,america2 this island1 it is most likely1 was cut off from ,hayti4 ,the ,isthmian region was considerably broader than it is now and afforded a more convenient highway of intermigration4 ,costa ,rica was invaded by a ,pliocene gulf1 but it is not yet clear whether this persisted for the whole or only a part of the epoch4 ,in the ,argentine province of ,entrerios is a formation1 the ,paran1 which is most probably ,pliocene1 though it may be upper ,miocene4 ,this formation is largely marine and shows that the present ,rio de la ,plata was then a gulf from the ,atlantic4 ,a few northern hemisphere mammals in the ,paran beds show that the migration had advanced far into ,south ,america4 ,a large part of ,patagonia was again submerged beneath the sea1 which extended to the ,andes in places1 but just how general the submergence was1 it is impossible to say1 for the ,cape ,fairweather formation has been largely carried away by erosion and only fragments of it remain4 ,along the foothills of the ,andes these beds are upturned and raised several thousand feet above the sea-level1 a proof that the final upheaval of the southern mountains took place at some time later than the early ,pliocene4 ,continental formations of ,pliocene date are largely developed in ,argentina2 the ,araucanian stage is in two substages1 one in the province of ,catamarca1 where the beds are much indurated and were involved in the ,andean uplift1 the other1 of unconsolidated materials1 is at ,monte ,hermoso near ,bahia ,blanca on the ,atlantic coast4 ,the very small proportion of northern animals in the ,araucanian beds is surprising1 but not more so than the almost complete absence of ,south ,american types in the upper ,miocene and lower ,pliocene of the ,united ,states4 ,intermigration between the two ,americas would seem to have been a much slower and more difficult process than between ,north ,america and the ,old ,world1 and the reason for the difference is probably the greater climatic barriers involved in a migration along the lines of longitude4 ,upper ,pliocene is found in the ,tarija ,valley of ,bolivia and probably also in ,ecuador1 in both of which areas the proportion of northern animals was very greatly increased4 ,,ii4 ,,quaternary ,,period ,the ,quaternary period was a time of remarkable geographical and climatic changes1 which had the profoundest and most far-reaching effects1 partly by migration and partly by extinction1 upon the distribution of animals and plants1 effects which are naturally more obvious than those of earlier geological events1 just because they were the latest4 ,it is customary to divide the period into two epochs1 7#a7 the ,pleistocene or ,glacial1 and 7#b7 the ,recent1 which continues to the present day4 #a4 ,pleistocene ,epoch ,when ,louis ,agassiz first suggested 7#ahdj7 the idea of a time1 comparatively recent in the geological sense1 when northern and central ,europe was buried under immense sheets of slowly moving ice1 like the 8ice-cap0 of modern ,greenland1 the conception was received with incredulity4 ,nearly thirty years passed before this startling theory gained the general acceptance of geologists1 but now it is one of the commonplaces of the science1 for no other hypothesis so well explains the complicated phenomena of ,pleistocene geology4 ,one great obstacle to the acceptance of the glacial theory was the supposed fact that the ,pleistocene glaciation was something quite unique in the history of the earth1 a violent aberration in the development of climates4 ,now1 however1 we have every reason to believe that at least three other and very ancient periods had witnessed similar climatic changes and that 8ice-ages0 were recurrent phenomena4 ,this is not the place to discuss or even to summarize the evidence which has convinced nearly all geologists of the reality of ,pleistocene glacial conditions on a vast scale in ,asia1 ,europe and1 above all1 in ,north ,america4 ,the reader who may wish to examine this evidence will find an admirable presentation of it in ,vol4 ,,iii of the 8,geology0 of ,professors ,chamberlin and ,salisbury4 ,north ,america4--,there has long been a difference of opinion among students of the ,pleistocene as to whether the glaciation was single1 or several times renewed4 ,that there were many advances and retreats of the ice1 is not denied2 the question is1 whether there were truly interglacial stages1 when the ice altogether disappeared from the continent and the climate was greatly ameliorated4 ,the present tendency among ,american and ,european geologists is decidedly in favour of accepting several distinct glacial stages 7,chamberlin and ,salisbury admit six of these7 separated by interglacial stages1 and for this there are very strong reasons4 ,while it is out of the question to present the evidence for this conclusion here1 one or two significant facts may be noted4 ,on the north shore of ,lake ,ontario1 near ,toronto1 are certain water-made deposits1 which rest upon one sheet of glacial drift and are overlaid by another4 ,the fossils of the aqueous sediments are in two series1 upper and lower1 of which the older and lower contains plants and insects indicative of a climate considerably warmer than that of the same region to-day and corresponding to the temperature of modern ,virginia4 ,in the upper and newer beds the fossils show the return of cold conditions1 much like those of southern ,labrador1 and this was followed by the restablishment of the ice1 as recorded in the upper sheet of drift4 ,even far to the north1 on the ,hudson's ,bay slope1 an interglacial forest is embedded between two glacial drift-sheets4 ,in ,iowa and ,south ,dakota numerous mammals of temperate character occur in interglacial beds4 ,at the time of their greatest extension1 the glaciers covered ,north ,america down to latitude #dj ,n41 though the great terminal moraine1 which marks the ice-front and has been traced across the continent from ,nantucket to ,british ,columbia1 describes a very sinuous line4 ,the ice was not a homogeneous sheet1 moving southward as a whole1 but flowed in all directions away from several1 probably four1 centres of accumulation and dispersal4 ,at the same time1 the western mountain ranges had a far greater snow-supply than at present1 and great glaciers flowed down all the valleys of the ,rocky ,mountains as far south as ,new ,mexico and in the ,sierras to southern ,california1 while the ,wasatch1 ,uinta and ,cascade ranges and those of ,british ,columbia and ,alaska were heavily glaciated1 but1 strange to say1 the lowlands of ,alaska were free from ice4 ,during the periods of greatest cold the rain-belt was displaced far to the south of its normal position1 bringing a heavy precipitation to regions which are now extremely arid4 ,in the ,great ,basin were formed two very large lakes2 on the east side1 rising high upon the flanks of the ,wasatch ,mountains1 was ,lake ,bonneville1 the shrunken and pygmy remnant of which is the ,salt ,lake of ,utah1 and on the west side1 in ,nevada1 was ,lake ,lahontan4 ,lake ,bonneville1 which was nearly two-thirds the size of ,lake ,superior1 discharged northward into the ,snake ,river1 a tributary of the ,columbia1 but ,lahontan had no outlet4 ,each of these lakes had two periods of expansion1 with a time of complete desiccation between them4 ,over the ,great ,plains the principal ,pleistocene formation is that known as the ,sheridan1 or1 from the abundance of horse-remains which are entombed in it1 the ,equus ,beds4 ,these beds extend as a mantle of wind-drifted and compacted dust from ,south ,dakota to ,texas and in places contain multitudes of fossil bones2 they correspond to one of the early interglacial stages and in ,south ,dakota pass underneath a glacial moraine4 ,the upheaval which came at or near the end of the ,pliocene had raised the continent1 or at least its northeastern portion1 to a height considerably greater than it has at present1 and this must have facilitated the gathering of great masses of snow2 but before the end of the ,pleistocene a subsidence of the same region brought about important geographical changes4 ,the depression1 which lowered the coast at the mouth of the ,hudson about #gj feet below its present level1 increased northward to #fjj feet or more in the ,st4 ,lawrence ,valley and allowed the sea to invade that valley and enter ,lake ,ontario4 ,from this gulf ran two long1 narrow bays1 one far up the valley of the ,ottawa and the other into the basin of ,lake ,champlain4 ,the raised beaches1 containing marine shells and the bones of whales1 seals and walruses1 give eloquent testimony of those vanished seas4 ,the recovery from this depression and the rise of the continent to its present level inaugurated the ,recent epoch4 ,when the ice had finally disappeared1 it left behind it great sheets of drift1 which completely changed the surface of the country and revolutionized the systems of drainage by filling up the old valleys1 only the largest streams being able to regain their former courses4 ,hundreds of buried valleys have been disclosed by the borings for oil and gas in the ,middle ,west1 and these1 when mapped1 show a system of drainage very different from that of modern times4 ,innumerable lakes1 large and small1 were formed in depressions and rock-basins and behind morainic dams1 the contrast between the glaciated and non-glaciated regions in regard to the number of lakes in each being very striking4 ,on the west coast events were quite different2 marine ,pleistocene beds in two stages are found in southern ,california4 ,the upheavals late in the ,pleistocene1 or at its close1 were far greater than on the ,atlantic side1 #djjj feet in southeastern ,alaska1 #bjj feet on the coast of ,oregon and rising again to #cjjj feet in southern ,california2 all the western mountain ranges and plateaus were increased in height by these movements4 ,the volcanoes continued to be very active1 as may be seen from the lava-sheets and streams in ,alaska1 all the ,pacific states1 ,arizona and ,new ,mexico4 ,south ,america4--,no such vast ice-sheets were formed in the southern hemisphere as in the northern4 ,patagonia was the only part of ,south ,america to be extensively covered with ice and there traces of three glaciations have been observed1 of which the first was the greatest and reached to the ,atlantic coast1 and there were great ice-masses on the coast of southern ,chili4 ,mountain glaciers existed throughout the length of the ,andes across the ,equator to #aa ,n4 lat41 the elevation increasing northward to the tropics4 ,the surface of the great ,argentine plain of the ,pampas between #cj and #dj ,s4 lat4 is covered with a vast mantle1 largely of wind-accumulated dust1 the ,pampean1 which is the sepulchre of an astonishing number of great and strange beasts4 ,the ,pampean formation corresponds in a general way to the ,sheridan or ,equus ,beds of ,north ,america1 but involves a much greater lapse of time1 beginning earlier1 possibly in the late ,pliocene1 and apparently lasting through the entire ,pleistocene4 ,while largely of olian origin1 the ,pampean seems to be in part made of delta deposits laid down by rivers4 ,one striking difference between the ,pampean1 on the one hand1 and the ,sheridan and the loess of the ,mississippi ,valley and of ,europe1 on the other1 is that the former is in many places much more consolidated and stony1 which gives it a false appearance of antiquity4 ,another and very rich source of ,pleistocene mammals is found in the limestone caves of eastern ,brazil1 which have yielded an incredible quantity of such material1 but not in such a remarkably perfect state of preservation as the skeletons of the ,pampean4 ,very little is known of the ,pleistocene in the ,west ,indies1 though probably to this date should be assigned the notable oscillations of level which are recorded in the raised sea-terraces of ,cuba and other islands4 ,the ,windward groups were joined1 at least in part1 to the continent and large extinct rodents reached ,antigua1 which would not be possible under present conditions4 ,the ,isthmus of ,panama was #bjj feet or more higher than it is now and correspondingly wider1 but was depressed to a lower than the present level1 and finally raised to the height it now has4 ,marine beds1 of presumably ,pleistocene date and certainly not older1 extend from the ,caribbean shore to ,gatun1 some seven miles1 and are nowhere more than a few feet above sea-level4 ,the question of ,pleistocene climates is a very vexed one and is far from having received a definitive answer4 ,limitations of space forbid a discussion of the problem here and ,i shall therefore merely state the conclusions which seem best supported by the evidence so far available4 ,such immense accumulations of ice might be due either to greatly increased snow-fall1 or to a general lowering of the temperature4 ,the balance of testimony is in favour of the latter factor and no great refrigeration is required4 ,professor ,penck has calculated that a reduction of #f or #g in the average yearly temperature would restore glacial conditions in ,europe4 ,even the tropics were affected by the change1 as is shown not only by the glaciation of the ,andes1 but also by ,mt4 ,kenya1 which is almost on the ,equator in eastern ,africa and still has glaciers4 ,the presumably ,pleistocene ice covered the whole mountain like a cap1 descending #edjj feet below the present glacier limit4 ,it was pointed out above that the interglacial stages had greatly ameliorated climatic conditions and that1 in some of them at least1 the climate was warmer than it is to-day in the same localities4 ,the cause of these astonishing fluctuations and of the climatic changes in general1 to which ,geology bears witness1 still remains an altogether insoluble mystery4 ,,chapter ,,vi ,,the ,,geographical ,,distribution ,,of ,,mammals ,to every one who has paid the slightest attention to the subject1 it is a familiar fact that different parts of the earth have different animals2 school-children learn from their geographies that kangaroos are found in ,australia1 the ,hippopotamus in ,africa1 the ,tiger in southern ,asia1 armadillos and llamas in ,south ,america4 ,these examples are all taken from distant lands1 yet the zological difference between two given land-areas is by no means proportional to the distance between them4 ,an ,englishman landing in ,japan finds himself surrounded by animals and plants very like and often identical with those which he left at home1 while the narrow ,strait of ,lombok1 east of ,java1 separates two profoundly different regions4 ,in crossing ,mexico from east to west1 the traveller meets very different animals in closely adjacent areas2 and1 at first sight1 the arrangement of animals appears to be so capricious as to admit of no formulation in general laws4 ,in pre-,darwinian times1 when it was the almost universal belief that each species had been separately created and was exactly fitted to the region which it inhabits1 no explanation of the geographical arrangement of animals was possible1 but the acceptance of the theory of evolution demanded that such an explanation should be found4 ,a failure to devise any rational and satisfactory account of the geography of animal life would be a fatal weakness in the evolutionary theory1 hence the facts of distribution were subjected to a renewed and searching analysis as one of the best means of critically testing the new doctrine4 ,not that the subject had received no attention before the publication of ,darwin's book2 on the contrary1 it had attracted much interest as a study of facts1 and this study was one of the principal avenues by which ,darwin approached his great generalization4 ,in his autobiographical fragment he tells us3 8,i had been deeply impressed by discovering in the ,pampean formation great fossil animals covered with armour like that on the existing armadillos2 secondly1 by the manner in which closely allied animals replace one another in proceeding southward over the ,continent2 and third1 by the ,south ,american character of most of the productions of the ,galapagos archipelago and more especially by the manner in which they differ slightly in each island of the group40 ,obviously1 before attempting to explain the facts of the geographical distribution of mammals1 we must first ascertain what those facts are4 ,the following brief sketch of the terms used in describing geographical arrangement is summarized from ,mr4 ,wallace's 8,island ,life40 ,though with fluctuating boundaries and subject to slow secular changes1 a mammalian species is limited to a fairly definite area1 which may be of immense or very restricted extent1 and throughout which it may be found in greater or less abundance4 ,many species1 however1 are not distributed continuously over the areas which they inhabit1 but occur only in suitable stations adapted to their habits and mode of life4 ,thus1 some will be found only where there are trees1 others in the neighbourhood of water1 others only on open plains1 etc4 ,a specific area is then the whole extent of country within which the species may be found1 while the stations are the limited districts contained in the area which are exactly suited to the habits of the species in question2 these stations may be hundreds of miles apart1 as in the case of mountain-tops1 or they may be close together4 ,a marsh-living species1 for example1 will occur in all the marshes throughout its area1 whether these be many or few1 near together or widely scattered2 for such a species marshes are its stations4 ,generic areas differ in character according as the genus is large1 that is1 comprising many species1 or small and having but few species1 or1 it may be1 a single one4 ,the species1 as a rule1 occupy each its own area1 and the areas may be entirely distinct1 or they may be contiguous and more or less extensively overlapping1 though it seldom happens that two or more species of the same genus inhabit exactly the same area4 ,often some physical feature1 such as a range of high mountains1 a great river1 the edge of a forest1 plain or desert1 exactly defines the limits of species of the same genus4 ,the ,amazon1 for example1 acts as such a boundary to many species4 ,it was to this change of related species from one area to another that ,darwin referred in the passage quoted above1 saying that he had been deeply impressed 8by the manner in which closely allied animals replace one another in proceeding southward over the ,continent i4e4 ,south ,america40 ,on the other hand1 the overlapping of areas may be very extensive1 and one species of great range may cover the whole area of another and much more besides4 ,a remarkable example of the widely separated areas of species belonging to the same genus is that of the tapirs4 ,of this genus there are two or three species in ,central and ,south ,america and one inhabiting the ,malay ,peninsula and ,borneo1 almost as wide a separation as the size of the earth permits4 ,discontinuous distribution of this character can be explained in terms of the evolutionary theory only in one of two ways4 ,either 7#a7 the ,american and ,asiatic species developed independently of one another from different ancestors1 or 7#b7 the regions intervening between these widely separated areas once formed a continuous land1 occupied by species of the genus which have become extinct4 ,from all that we know concerning the operation of the evolutionary process1 the first alternative may be set aside as altogether improbable1 and1 even had we no information concerning the history of the tapirs and their former distribution1 the second explanation would be chosen as incomparably the more likely4 ,as a matter of fact1 we have definite knowledge that tapirs once ranged all over ,europe and ,north ,america and doubtless over northern ,asia1 as well1 and1 further1 that ,north ,america was joined to ,asia by a land occupying the place of the shallow ,bering ,sea1 at a time when the tapirs were able to take advantage of this means of passing from one continent to the other4 ,such appears to be the invariable explanation of discontinuous distribution1 though we may not always be able to give so clear a proof of it4 ,the genera of a family are distributed in much the same fashion as the species of a genus1 but1 as a rule1 much more widely4 ,while no genus of terrestrial mammals is cosmopolitan 7i4e4 universally distributed71 at least as genera are defined and limited by most modern systematists1 certain families are represented in every continent4 ,if the extremely peculiar and isolated ,australian continent be excepted1 the number of such cosmopolitan families is considerable and wide separation between the genera is frequent4 ,of the camel family1 for instance1 one genus1 that of the true ,camel 7,camelus71 is confined to the northern hemisphere and the ,old ,world1 the other 7,lama71 comprising the ,llama1 ,guanaco1 etc41 is found only in the southern hemisphere and the ,new ,world4 ,less extreme instances of the discontinuous distribution of a family are common enough4 ,the principles of distribution are the same when applied to families and orders4 ,most of the mammalian orders are very widely distributed and many are cosmopolitan1 except for ,australia1 though some are confined to one or two continents4 ,the monotremes are limited to ,australia and ,tasmania1 the marsupials to ,australia and the ,americas1 the edentates to the latter1 the elephants and hyracoids to ,africa and ,asia4 ,carnivores and rodents1 on the contrary1 are found in every continent1 even ,australia4 ,we have next to inquire what is the nature of the obstacles or barriers that prevent the indefinite spread of terrestrial mammals1 so that the mammalian fauna of the whole earth1 and even of a single continent1 is not uniform1 but highly variegated4 ,the rate of multiplication of animals is so rapid that1 under normal conditions1 the animal population is always pressing hard upon the means of subsistence and every species that is increasing in numbers must constantly extend its range in search of food4 ,every species would increase indefinitely1 if there were no countervailing checks4 ,were all the young to survive and breed in their turn1 8even large and slow-breeding mammals1 which only have one at a birth1 but continue to breed from eight to ten successive years1 may increase from a single pair to #aj1jjj1jjj in forty years0 7,wallace74 ,evidently1 a species must spread from its place of origin until stopped by insuperable obstacles1 the most obvious of which are wide seas4 ,a few land mammals are not only excellent swimmers1 but will cross straits without hesitation1 as the ,guanaco has been seen to swim the ,straits of ,magellan2 for the great majority1 however1 a very few miles of sea form an impassable barrier4 ,as was shown above1 a broad or deep river is sufficient to limit many species1 as the ,santa ,cruz ,river in ,patagonia marks the southern boundary of the armadillos4 ,important geographical changes1 such as the joining of lands that before were separate1 or the dividing of continuous lands by transgressions and incursions of the sea1 must necessarily have a profound effect upon the distribution of land mammals4 ,separated land-areas1 however similar may have been their faunas at the time of separation1 will1 through the operation of the divergent evolutionary process1 grow more unlike in proportion to the length of time that the separation continues4 ,regions which have been severed within a short time 7in the geological sense of a short time7 are zologically very similar or even identical1 while those that have long been isolated are correspondingly peculiar4 ,attention has already been called1 in another connection1 to the contrasted cases of such great continental islands as ,great ,britain1 ,java1 ,sumatra1 etc41 on the one hand1 and ,australia1 on the other4 ,the continental islands1 which have but lately been detached from the neighbouring main lands1 are hardly more peculiar zologically than equal areas of the adjoining continents1 while the long-continued isolation of ,australia has made it the most peculiar region of the earth4 ,climatic changes1 which1 as we saw in ,chapter ,i1 have indubitably taken place many times1 have also had a great effect in shifting the distribution of mammals1 which in its present form is the outcome of a very long series of geographical and climatic changes1 on the one hand1 and of adaptive changes in the animals themselves1 on the other4 ,of almost equal importance as a barrier is climate and especially temperature4 ,not that similar climates can produce similar forms in separate areas4 ,regions of almost exactly similar climate in ,australia1 ,africa and ,south ,america have totally different faunas1 but1 within continuous land-areas1 the most effective of barriers is temperature4 ,this acts differently in the case of limiting the northward spread of southern forms and the southward spread of northern species4 ,dr4 ,merriam's long study of this problem has led him to the conclusion that southern species are bounded on the north by the temperature of the breeding season1 in which the total quantity of heat must reach a certain minimum1 while 8animals and plants are restricted in southward distribution by the mean temperature of a brief period covering the hottest part of the year40 ,on the ,pacific coast there is a remarkable mingling in the same areas of species which1 east of the high mountains1 are distributed in sharply separated zones4 ,this is explained by the mild and equable climate of the coastal belt1 where the hottest season of the year does not reach the limiting maximum for the northern species1 while the total quantity of heat in the breeding season is sufficient to enable southern species to thrive and maintain themselves4 ,dr4 ,merriam thus sums up the effects of climatic factors upon distribution3 8,humidity and other secondary causes determine the presence or absence of particular species in particular localities within their appropriate zones1 but temperature pre-determines the possibilities of distribution2 it fixes the limits beyond which species cannot pass40 8,concurrently with these changes in vegetation from the south northward occur equally marked differences in the mammals1 birds1 reptiles1 and insects4 ,among mammals the tapirs1 monkeys1 armadillos1 nasuas1 peccaries1 and opossums of ,central ,america and ,mexico are replaced to the northward by wood-rats1 marmots1 chipmunks1 foxes1 rabbits1 short-tailed field-mice of several genera1 shrews1 wild-cats1 lynxes1 short-tailed porcupines1 elk1 moose1 reindeer1 sables1 fishers1 wolverines1 lemmings1 musk-oxen1 and polar bears40 ,dr4 ,j4 ,a4 ,allen has reached closely similar conclusions4 8,of strictly climatic influences1 temperature is by far the most important1 although moisture plays an influential part4 ,where a low temperature prevails life1 both animal and vegetable1 is represented by comparatively few forms2 under a high temperature it is characterized by great diversity and luxuriance4 ,within the ,arctic ,circle the species of both animals and plants are not only few1 but they are widely distributed1 being for the most part everywhere the same4 ,under the tropics they are a hundred fold more numerous and of comparatively restricted distribution40 8,the influence of temperature is perhaps most strikingly displayed in the distribution of life upon the slopes of a high mountain1 especially if situated near the tropics4 ,while its base may be clothed with palms and luxuriant tropical vegetation1 its summit may be snow-capped and barren4444 ,the animal life becomes likewise correspondingly changed1 tropical forms of mammals1 birds1 and insects of the lower slopes gradually giving place to such as are characteristic of arctic latitudes40 8,the effect of humidity upon plant life is thus obvious1 but it is equally potent1 though less evident1 upon animal life4 ,many animals 444 are so fitted for a forest life1 as regards both food and shelter1 that their very existence depends upon such surroundings4444 ,thus moisture alone may determine the character of life over extensive regions40 ,while climate is thus the most important of the barriers which determine distribution in continuous land-areas1 the absence of any particular species from a given region is no proof that the climate is unsuitable to that species4 ,this is sufficiently shown by the manner in which animals introduced into a new country often run wild and multiply to an incredible extent1 as the rabbits have done in ,australia1 the ,mongoose in ,jamaica1 horses on our western plains1 horses and cattle on the ,pampas of ,argentina1 etc4 ,topographical features1 such as great mountain-ranges and plateaus1 also limit many species1 not only by the difficulty of crossing them1 but also by the effect which they have upon temperature and moisture4 ,for this reason long ranges of mountains and table-lands may carry a northern fauna very far to the south of its ordinary range1 as do the mountain-systems of ,north ,america in a very conspicuous manner4 ,the great ,mexican plateau is zologically a part of ,north ,america1 while the low coastal lands as far as southeastern ,texas have ,central ,american affinities4 ,a different kind of obstacle to the spread of a species into a new area may be the pre-occupation of that area by another species4 ,the pre-occupier may be one that plays so similar a part in the economy of nature as to leave no opportunity for the newcomer to establish itself4 ,on the other hand1 the obstructing form may be an active enemy and of a totally different character from the intruder1 as in the case of the ,tse-tse ,fly in parts of ,africa4 ,the bite of the fly is fatal to horses and oxen1 so that these mammals are unable to enter the fly-infested regions4 ,many times in the course of the ,tertiary period various mammals reached ,north ,america from the south or from the ,old ,world1 which were unable to gain a permanent foothold and speedily died out4 ,at this distance of time it is seldom1 if ever1 possible to explain why a species which succeeded in reaching this continent could not maintain itself1 though the most probable assumption is that the forms already in possession of the land were an insuperable obstacle to the intruders4 ,the rate of dispersal of a species into new areas may be fast or slow1 according as the conditions are more or less favourable4 ,newly introduced insect-pests1 like the ,gypsy and the ,brown-tailed ,moths in ,new ,england1 often spread with portentous rapidity2 and introduced mammals have frequently taken possession of vast areas in a surprisingly short time4 ,one of the most remarkable of these cases is cited by ,darwin4 8,in the time of ,sarmiento 7#aehj7 these ,indians had bows and arrows1 now long since disused2 they then also possessed some horses4 ,this is a very curious fact1 showing the extraordinarily rapid multiplication of horses in ,south ,america4 ,the horse was first landed at ,buenos ,ayres in #aecg and the colony being then for a time deserted1 the horse ran wild2 in #aehj1 only forty-three years afterwards1 we hear of them at the ,strait of ,magellan60 78,voyage of a ,naturalist10 pp4 #bcb-bcc47 ,in this example1 something must be allowed for human agency1 but even so1 it is very surprising4 ,in the case of lands newly raised above the sea and connecting formerly separated areas1 it is necessary that they should first be taken possession of by vegetation1 before they can become passable by animals1 for the migration of mammals from continent to continent is an entirely distinct phenomenon from the annual migration of birds4 ,the latter1 though a fact familiar to every one1 is an unexplained mystery1 and it is somewhat unfortunate that the same term should be used for the completely different process of the spread of mammals into newly opened land4 ,this spread is purely unconscious and is due to the pressure of increasing numbers upon the means of subsistence1 each new generation ranging farther and farther from the original home of the species and continuing so to extend until some insuperable obstacle is encountered4 ,when a sea-barrier is removed by upheaval and the newly formed land rendered habitable for mammals through the invasion of plants1 the interrupted process is resumed and an interchange of species between the areas thus connected is brought about4 ,the interchange is1 however1 always an incomplete one1 certain forms not being able so to extend their range1 because of climatic differences1 pre-occupation or some such barrier4 ,it is customary to give a graphic expression to the facts of animal distribution by dividing the land surface of the earth into districts which are characterized by their faunas4 ,it is not possible to construct a geographical scheme which will be equally satisfactory for all classes of animals1 because the geological date of most rapid development and diffusion was so different in the various classes4 ,the geographical and climatic conditions which favoured a particular geographical arrangement of one class had been so completely altered that the class coming in later could not attain a similar distribution4 ,for this reason1 land mammals are chosen as affording the best criteria2 their adaptability is such that they are found all over the earth1 their dispersal is primarily dependent upon the arrangement and connections of the continental land-masses1 modified by the topographical and climatic conditions1 and they1 with the birds1 are the latest of the vertebrate classes to assume a dominating importance4 ,their history is the most fully known and falls within the best understood portion of the earth's history1 making it possible to follow their migrations with a precision which is seldom feasible for the other classes of animals1 and thus to correlate the successive physical and organic changes4 ,a particularly great advantage which mammals possess for this purpose is that the mutual relationships of the various kinds are better understood than in the case of most other groups of animals4 ,it is true that we shall find a great many unsolved problems1 upon which the most divergent opinions are held1 but the main outlines of the scheme are quite generally agreed upon4 ,many plans for the zological division of the continental areas have been proposed by various writers on the subject1 some differing very radically from others4 ,it would be useless and tedious to review even the more important of the many proposals and suggestions which have been made in the last half-century2 and we may1 with advantage1 adopt an eclectic scheme which has been slowly reached by successive approximations to a satisfactory arrangement4 ,just as in political geography it is found necessary to recognize divisions of different rank and scope1 like nation1 state1 county1 township1 the facts of zological geography require divisions of different orders of importance4 ,thus1 in descending order1 the terms realm1 region1 subregion1 province1 etc4 are commonly employed1 but unfortunately they are often used loosely and even interchangeably2 yet it is desirable to attach a more or less precise significance to each and more terms are needed for an accurate expression of the many complex facts4 ,the extreme zological peculiarity of ,australia is recognized by making that continent and its adjoining islands one of the great primary divisions1 of which the other includes all the rest of the world2 the former is characterized by its almost exclusively marsupial fauna1 while the other continents are inhabited by the ,monodelphia or placental mammals4 ,aside from ,australia1 by far the most isolated and peculiar region of the earth is ,south ,america1 and this fact is expressed by constituting it into a realm1 or division of the second order1 and to this realm is given the name ,neoga4 ,the remaining continents1 ,north ,america1 ,europe1 ,asia and ,africa1 make up the other realm1 ,arctoga1 in which there is an unmistakable general likeness among the mammals4 ,the three continents of the ,old ,world form a vast1 connected land-mass1 and the final separation of ,north ,america from this great complex is an event of geologically recent date4 ,for reasons that will be made clear in the course of the history1 the junction of the two ,americas has had comparatively little effect upon the zology of the northern continent1 except in its tropical portion4 ,it is obvious from a glance at the map1 that the great zological divisions are of very unequal size1 but the arrangement is made on the basis of degrees of difference in the mammalian faunas4 ,these degrees of difference are1 in turn1 an expression of length of separation or of the difficulty of communication between connected lands4 ,the following table gives the major divisions of the earth apart from ,australia3 ,i4 ,,neog,,ic ,,realm4 ,neotropical ,region4--,south and ,central ,america1 lowlands of ,mexico1 the ,west ,indies4 ,,ii4 ,,arctog,,ic ,,realm4 #a4 ,malagasy ,region4--,madagascar4 #b4 ,ethiopian ,region4--,africa south of the ,sahara ,desert4 #c4 ,oriental ,region4--,southern peninsulas of ,asia1 ,malay ,archipelago4 #d4 ,holarctic ,region4--,n4 ,africa1 ,europe1 ,asia1 7except southern part71 boreal ,n4 ,america4 #e4 ,sonoran ,region4--,remainder of ,n4 ,america 7except lowlands of ,mexico74 ,north ,america1 as is expressed by this scheme1 is zologically composite2 the northern half1 including nearly all of ,canada1 belongs to the vast ,holarctic ,region1 which also comprises ,europe1 ,africa north of the ,sahara and ,asia north of the ,himalaya ,mountains4 ,the remainder of the continent1 exclusive of the ,mexican coastal lowlands1 is set off as the ,sonoran ,region4 ,inasmuch as we have here to do with broadly continuous land-areas1 not demarcated by great physical features1 and as the genera and species of mammals differ greatly in regard to their ability to withstand a wide range of climatic variations1 it is not to be expected that the boundaries between the regions which make up ,north ,america should be very sharply drawn4 ,it is not surprising1 therefore1 to find a transition zone1 extending all across the continent1 in which the ,holarctic and ,sonoran faunas mingle1 or that ,central ,america should1 in considerable measure1 be transitional to ,south ,america1 though zologically a part of the latter4 ,illustration3 ,,fig4 #ec4--,zological ,divisions of ,north ,america4 7,after ,merriam47 ,dr4 ,merriam's arrangement1 which deals only with ,north ,america without reference to the ,old ,world1 divides the land into a series of transcontinental zones1 which he calls the ,arctic1 ,boreal1 ,upper and ,lower ,sonoran and ,tropical4 ,these zones have very irregular and sinuous boundaries1 which follow lines of equal temperature 7isothermal lines7 during the breeding season1 ,may1 ,june and ,july1 the tortuous boundaries being conditioned by topographical features1 which deflect the isothermal lines4 ,illustration3 ,,fig4 #ed4--,polar ,bear 7,thalarctus maritimus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the ,arctic zone is part of a circumpolar area1 which is very much the same in ,north ,america1 ,asia and ,europe2 and in any of these continents the fauna differs much more from that of the contiguous zone to the south than from the ,arctic fauna of another continent4 ,there are some local differences1 but the characteristic mammals of this ,arctic zone are the ,polar ,bear1 ,arctic ,fox1 ,musk ,ox1 ,barren-ground ,caribou1 ,lemming1 ,arctic ,hare1 and a marmot4 ,most1 if not all1 of these forms are of ,old ,world origin4 ,illustration3 ,,fig4 #ee4--,musk ,ox 7,ovibos wardi7 female2 the males have much larger horns4--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ef4--;,arctic ,fox 7,vulpes lagopus7 in winter dress4--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #eg4--;,arctic ,fox in summer dress4--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the ,american portion of the great ,holarctic region is called by ,mr4 ,lydekker1 who uses ,wallace's term1 the 8,canadian subregion10 and by ,dr4 ,merriam the 8,boreal region40 ,not that there is any difference of principle involved in this varying nomenclature1 for ,dr4 ,merriam says3 8,it so happens that the ,boreal element in ,america resembles that of ,eurasia so closely that in the judgment of many eminent authorities the two constitute a single primary region--a view in which ,i heartily concur40 ,the ,canadian or ,boreal subregion of the ,holarctic is the great belt of coniferous forest1 which extends obliquely across ,north ,america from ,alaska to ,new ,england2 its frontier with the ,arctic zone is the northern limit of trees and it is divided from the ,transition zone approximately by the line of latitude #de ,n41 though with a sinuous course1 and it is carried far to the south by the wooded heights of the ,appalachian1 ,rocky and ,sierra ,nevada ,mountains1 and along the ,pacific coast1 the mixed character of which has already been explained2 it extends almost to ,san ,francisco4 ,the subregion is further divisible into northern and southern belts1 called the ,hudsonian and ,canadian faunas1 the limit between them approximately following the isothermal line of #eg ,f4 ,the mammals of this subregion are largely of ,old ,world origin1 many of them coming in with the great immigrations of the ,pliocene and ,pleistocene epochs2 but there are also native ,american elements and even one genus of ,south ,american origin1 the ,short-tailed or ,canada ,porcupine 7,erethizon74 ,illustration3 ,,fig4 #eh4--;,canada ,porcupine 7,erethizon dorsatus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ei4--,woodchuck or ,marmot 7,marmota monax74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fj4--,mink 7,lutreola vison74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,in considering the mammals of this subregion1 it should be remembered that they are not uniformly distributed throughout even one subdivision1 but in a scattering way and in accordance with their habits and stations1 and also in accordance with a gradual change to the south1 following the changing temperature4 ,the ,muskrat will not be found far from water or the ,porcupine from woods4 ,especially characteristic of the ,canadian subregion are the ,old ,world types of deer1 none of which range farther south than the ,transition zone4 ,the ,wapiti1 erroneously called the ,elk 7,cervus canadensis71 is very closely allied to the ,european ,stag 7,c4 elaphus7 and still more closely to the ,stag of the ,thian ,shan in ,central ,asia 7,c4 eustephanus74 ,so great is the resemblance1 that some naturalists would refer all three forms to a single species4 ,the ,moose 7,alce americanus71 which should be called the ,elk1 is so near to the ,scandinavian ,elk 7,a4 machlis7 that it is hardly distinguishable as a separate species1 and the ,woodland ,caribou 7,rangifer caribou7 is the ,american representative of the ,lapland ,reindeer 7,r4 tarandus74 ,the so-called ,rocky ,mountain ,goat 7,oreamnos montanus71 a peculiar and aberrant form of the ,chamois subfamily of the ,antelopes1 is confined to the subregion4 ,the ,mountain ,sheep 7,ovis montana1 ,o4 dalli7 are represented by three or four species1 one of which extends into the ,sonoran region1 as does also the ,bison1 wrongly called ,buffalo 7,bison bison71 which is nearly allied to the ,european ,b4 bonasus4 ,in ,csar's time the ,european ,bison 7,german1 ,wisent7 ranged through ,germany and is described in his account of the ,hercynian ,forest2 but the advance of civilization has almost exterminated it1 only a few small herds being maintained by the most rigid protection in ,russia and in the ,carpathian ,mountains4 ,of the ,carnivora1 the weasels1 martens1 ,fisher1 ,mink and ,ermine are ,boreal1 as are the ,wolverene 7,gulo7 and the ,grey ,wolf 7,canis71 the three last-named extending also into the ,arctic zone4 ,essentially ,boreal1 though reaching and entering the ,sonoran1 are the bears 7,ursus71 the red foxes 7,vulpes71 the otters 7,lutra7 and the ,old ,world shrews 7,sorex71 while the ,star-nose ,mole 7,condylura7 and the mole-shrews 7,urotrichus7 do not extend south of the ,transition zone4 ,probable intruders from the south into the ,boreal subregion are the pumas1 or 8mountain lions10 which just enter the subregion1 the ,canada ,lynx 7,lynx rufus7 and one species of skunks 7,mephitis71 the ,raccoon 7,procyon lotor71 ,badger 7,taxidea americana7 and the ,american deer 7,odocoileus74 ,a large number of rodents are characteristically ,boreal3 marmots1 or woodchucks 7,marmota71 the ,sewellel 7,aplodontia rufa71 lemmings 7,myodes71 ,jumping ,mouse 7,zapus71 the ,canada ,porcupine 7,erethizon dorsatus7 and the pikas1 8tailless or whistling hares0 7,ochotona74 ,boreal rodents that enter the ,sonoran are the chipmunks 7,tamias71 beavers 7,castor71 meadow-mice 7,microtus71 the ,muskrat 7,fiber zibethicus74 ,the white-footed mice 7,sitomys7 and the wood-rats 7,neotoma7 are southern rodents that reach or enter the ,boreal4 ,between the ,boreal subregion and the ,sonoran region is the ,transition zone1 which follows all the complex windings of the boundary lines4 ,it covers most of ,new ,england1 ,new ,york1 ,pennsylvania and southern ,ontario2 passing through southern ,michigan and ,wisconsin1 it bends northward over ,minnesota and covers most of ,north ,dakota1 ,manitoba and the plains of the ,saskatchewan1 then turns abruptly southward and includes eastern ,montana and parts of ,south ,dakota and ,nebraska4 ,crossing ,wyoming1 it follows around the northern edge of the ,great ,basin to the plains of the ,columbia4 ,the three great mountain-systems carry the zone far to the south and arms of it extend along the ,appalachians to northern ,georgia1 along the ,rockies to ,new ,mexico1 and it follows the ,sierras to southern ,california4 8,the ,transition zone1 as its name indicates1 is a zone of overlapping ,boreal and ,sonoran types4 ,many ,boreal genera and species here reach the extreme southern limits of their distribution and many ,sonoran genera and species their northern limits4 ,but a single mammalian genus 7,synaptomys7 one of the field mice is restricted to the ,transition zone4444 ,a number of species1 however1 seem to be nearly or quite confined to this zone0 7,merriam74 ,illustration3 ,,fig4 #fa4--,upper figure1 ,european ,bison 7,bison bonasus74 ,lower figure1 ,american ,bison 7,b4 bison74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fb4--,wolverene 7,gulo luscus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fc4--,wapiti or 8,elk0 7,cervus canadensis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fd4--;,alaska ,brown ,bear 7,ursus middendorfi74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fe4--,moose 7,alce americanus74 ,young male with undeveloped antlers4--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ff4--;,beaver 7,castor canadensis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fg4--,woodland ,caribou 7,rangifer caribou74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fh4--,red ,fox 7,vulpus fulvus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #fi4--,rocky ,mountain 8,goat0 7,oreamnos montanus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #gj4--;,ermine 7,mustela erminea74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ga4--,timber or ,grey ,wolf 7,canis nubilis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #gb4--;,boreal ,mammals4 ,a4 ,black-footed ,ferret 7,mustela nigripes74 ,b4 ,otter 7,lutra canadensis74 ,c4 ,jumping ,mouse 7,zapus hudsonius74--,a and ,b by permission of the ,n4,y4 ,zolog4 ,soc4 ,c1 by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #gc4--,opossum 7,didelphis marsupialis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the most characteristic portion of ,north ,america1 zologically speaking1 is the ,sonoran region of ,dr4 ,merriam1 the ,warm ,temperate of ,dr4 ,allen4 ,it crosses the continent from ocean to ocean1 its northern boundary following for most of the way the #dc;d parallel of latitude1 but over the ,great ,plains and ,great ,basin1 on each side of the ,rocky ,mountains and the high plateaus1 it extends to lat4 #dh4 ,on the south1 it takes in the greater part of ,mexico1 covering all of the table-land of that country1 the lowlands of which belong to the ,south ,american or ,neotropical region4 ,the ,sonoran is invaded from the north by the long branches from the ,boreal and ,transition zones1 which follow the three great mountain-systems in the manner already explained1 and the ,mexican plateau permits the similar invasion of ,neotropical territory by the ,sonoran fauna4 ,characteristic ,sonoran genera1 none of which extend into the ,boreal1 are the opossums 7,didelphis71 in the southern part a peccary 7,tagassu7 or 8,wild ,texas ,pig10 representative of a family of swine quite different from the true pigs of the ,old ,world1 and an armadillo 7,tatu74 ,a very isolated form is the ,prong-horned ,antelope 7,antilocapra americana72 there are several species of the typically ,american deer 7,odocoileus7 which differ in important respects from those of the eastern hemisphere1 and the ,bison was very abundant until exterminated by ,man4 ,bison1 antelope and deer also reach or extend into the ,boreal zone1 but the former1 or ,wood ,bison1 is probably a different species from the plains animal4 ,illustration3 ,,fig4 #gd4--,prong-horned ,antelope 7,antilocapra americana74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ge4--,kangaroo-,rat 7,dipodomys philippii74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #gf4--,thirteen-lined ,spermophile 7,spermophilus tredecimlineatus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the grey foxes 7,urocyon71 ,coyote 7,canis latrans71 large ,timber ,wolf 7,canis occidentalis71 the ,caxomistle 7,bassariscus71 the ,coati 7,nasua71 ,raccoon 7,procyon71 ,badger 7,taxidea71 three genera of skunks1 pumas1 several species of lynx and some bears 7,ursus7 represent the ,carnivora1 though one species each of raccoon1 skunk1 badger1 puma and lynx range into the ,boreal4 ,the ,american types of shrews 7,blarina7 and moles 7,scalops and ,scapanus7 are characteristic of the ,sonoran1 though partially shared with the ,boreal4 ,a great many peculiar rodents inhabit the ,sonoran2 cotton-rats 7,sigmodon71 pocket-gophers 7,geomys1 etc471 several genera of the beautiful little kangaroo-rats 7,dipodomys1 etc472 while the prairie-dogs 7,cynomys71 the white-footed mice 7,sitomys71 wood-rats 7,neotoma7 and one genus of pocket-gophers 7,thomomys7 are chiefly ,sonoran1 but have ,boreal representatives4 ,the flying squirrels 7,sciuropterus71 true squirrels 7,sciurus71 ground-squirrels 7,spermophilus71 rabbits 7,lepus71 wolves 7,canis7 and otters 7,lutra7 have a very wide range through both the ,boreal and ,sonoran1 but have many more species in the latter region4 ,illustration3 ,,fig4 #gg4--;,grey ,squirrel 7,sciurus carolinensis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the ,sonoran region may be divided into the upper and lower ,sonoran zones1 which are demarcated by temperature and are of transcontinental extent4 ,each of these zones may1 in turn1 be subdivided into arid and humid provinces1 but our purpose does not necessitate entering into such refinements4 ,illustration3 ,,fig4 #gh4--;,grey ,fox 7,urocyon virginianus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #gi4--,prairie ,wolf or ,coyote 7,canis latrans74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #hj4--,raccoon 7,procyon lotor74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ha4--,virginia ,deer 7,odocoileus virginianus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #hb4--,skunk 7,mephitis mephitis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #hc4--,mule ,deer 7,odocoileus hemionus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #hd4--;,badger 7,taxidea americana74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #he4--,puma or ,mountain ,lion 7,felis concolor74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #hf4--,lynx 7,lynx rufus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #hg4--,prairie-,dog 7,cynomys ludovicianus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the ,neotropical1 which is the only region of the ,neogic realm1 comprises the ,west ,indian islands1 all of ,central and ,south ,america and the lowlands of ,mexico1 extending a short distance into southeastern ,texas4 ,of its four subregions1 the most typical is 7#a7 the ,brazilian1 which includes not only ,brazil1 but all of ,south ,america east of the ,andes and as far south as ,paraguay1 and is a vast area of tropical forests4 7#b7 ,the ,chilian subregion takes in the west coast1 the high ,andes and the southern end of the continent1 south of the ,brazilian subregion2 it is a country chiefly of open plains and high mountains1 and a few deserts1 of which ,south ,america has less than any other continent1 except ,europe1 which has none4 7#c7 ,the ,central ,american subregion reaches from the ,isthmus of ,panama to ,mexico1 the lowlands of which are included and even a small portion of southeastern ,texas4 7#d7 ,the ,west ,indian subregion includes all the islands of that archipelago1 except ,trinidad1 which is a fragment of the continent1 detached at a comparatively recent date2 the southern extremity of ,florida also belongs to this subregion4 ,the two subregions into which continental ,south ,america is divided are not altogether satisfactory and will doubtless require change when the distribution of ,south ,american mammals has been more accurately determined4 ,illustration3 ,,fig4 #hh4--,map of the ,neotropical region4 7,after ,wallace47 ,mexico inaccurate2 cf4 ,fig4 #ec1 p4 #adg4 ,illustration3 ,,fig4 #hi4--;,fox-like ,wolf 7,cerdocyon gracilis74--,by permission of ,w4 ,s4 ,berridge1 ,london4 8,richness combined with isolation is the predominant feature of ,neotropical ,zology1 and no other region can approach it in the number of its peculiar family and generic types0 7,wallace74 ,just as ,north ,america has received many immigrants from the ,old ,world1 so it has sent many migrants into ,south ,america1 materially changing the character of the ,neotropical mammalian fauna1 but these intruders may be readily identified and almost seem to be out of place in their new surroundings4 ,not all of these northern migrants were able to maintain their footing in the southern continent and several became extinct during and at the close of the ,pleistocene epoch1 as was even more markedly the case with the southern forms which invaded the northern continent4 ,illustration3 ,,fig4 #ij4--,spectacled ,bear 7,tremarctos ornatus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,there are two families of monkeys in the forested areas of ,south ,america1 both very different from those of the ,old ,world4 ,one of these families1 the marmosets 7,hapalid71 differs from all other monkeys in several particulars1 most obvious of which are the long claws on the feet and the non-opposable thumb4 ,the second family 7,cebid7 comprises forms which are superficially much more like those of the eastern hemisphere1 but many of them have prehensile tails1 which are used as efficient grasping organs4 ,insectivora are entirely absent from the ,south ,american continent1 but some shrews 7,blarina7 have entered ,central ,america from the north and a very curious genus is represented by one species in ,cuba 7,solenodon cubanus7 and another in ,hayti 7,s4 paradoxus74 ,these remarkable animals are1 strange to relate1 most nearly allied to the tenrecs 7,centetes7 of ,madagascar and by some authorities are placed in the same family4 ,illustration3 ,,fig4 #ia4--,solenodon cubanus4--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ib4--;,argentine ,skunk 7,conepatus gibsoni74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #ic4--,little ,skunk 7,spilogale putorius74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,the ,carnivora are quite numerous and varied and rather peculiar1 but they all belong to northern families and are the more or less modified descendants of northern immigrants4 ,the dogs 7,canid7 belong to genera not represented elsewhere and form a considerable assemblage of interesting types4 ,there are no true wolves or foxes1 but several species of fox-like wolves 7,cerdocyon71 with bushy tails1 are common1 especially in the plains regions4 ,the ,bush-,dog 7,icticyon venaticus71 a small1 short-legged animal1 is very peculiar4 ,the musteline or weasel family 7,mustelid7 is rather scantily represented4 ,there are no badgers and but few skunks 7,spilogale and ,conepatus72 weasels are absent1 but their place is taken by the ,grison 7,galera vittata7 and ,tayra 7,tayra tayra7 and in the far south ,lyncodon patagonicus4 ,these animals are peculiar in having a lighter colouration on the back than on the belly4 ,there are two or three species of otter 7,lutra74 ,the raccoons 7,procyon7 have a very wide range in ,south ,america1 as in the northern continent1 and the curious1 long-snouted coatis 7,nasua71 which just enter the ,sonoran region1 are typically ,neotropical4 ,the ,spectacled ,bear 7,tremarctos ornatus7 is the only member of the family that occurs in ,south ,america and is confined to the highlands of ,peru and ,chili4 ,the cat family is quite numerously represented2 the ,jaguar 7,felis onca71 which ranges from ,texas to ,patagonia1 is a large spotted cat1 rivalling the ,leopard in size and ferocity2 the ,ocelot 7,f4 pardalis1 ,arkansas to ,paraguay7 is smaller and streaked and blotched rather than spotted4 ,the pumas differ little from those of ,north ,america1 and there are many small cats1 spotted1 clouded and of solid colour1 but no lynxes1 which are essentially northern types4 ,illustration3 ,,fig4 #id4--,tayra 7,tayra tayra74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #ie4--,kinkajou 7,potos caudivolvulus71 ,central ,america4--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #if4--,ocelot 7,felis pardalis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ig4--;,jaguar 7,felis onca74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ih4--;,collared ,peccary 7,tagassu tajacu74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,hoofed animals are not numerously represented in ,south ,america4 ,the only existing ,perissodactyla of the western hemisphere are the tapirs 7,tapirus7 of ,central and tropical ,south ,america1 a very remarkable contrast to the ancient faunas1 especially of the northern continent1 as will be shown in the sequel4 ,the ,artiodactyla are more varied1 though very scanty in comparison with those of the ,old ,world2 even ,north ,america1 which has but a poor representation of these animals1 is much richer than the southern continent1 where1 indeed1 all the hoofed animals are the descendants of comparatively recent immigrants from the north and none are truly autochthonous4 ,members of three different artiodactyl suborders occur in the ,neotropical region2 the peccaries 7,tagassu7 extend through ,central and ,south ,america to ,paraguay1 though also entering the ,sonoran region in ,texas4 ,most interesting are the members of the camel family1 which are very distinct from the true ,camel of ,asia4 ,tierra del ,fuego and the ,patagonian plains support great herds of the ,guanaco 7,lama huanacus71 which extends along the ,andes to ,ecuador and ,peru1 where it is associated with the ,vicua 7,l4 vicunia71 a smaller and more slenderly built species4 ,the ,vicua does not range south of ,bolivia4 ,just as the mountain systems of ,north ,america carry the ,boreal and ,transition faunas through nearly the whole breadth of the ,sonoran region1 so the high ,andes afford a pathway by which the mammals of the south temperate zone extend their range to the equator4 ,illustration3 ,,fig4 #ii4--,vicua 7,lama vicunia74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #ajj4--;,florida ,deer 7,odocoileus virginianus osceola74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #aja4--,marsh ,deer 7,blastoceros paludosus71 female4--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the suborder ,pecora of the ,artiodactyla is represented in the ,neotropical region only by the deer family 7,cervid71 of which there are several genera 7or subgenera71 all of them ,north ,american as distinguished from the ,old ,world type1 but some are so peculiar that they must have had a relatively long ,south ,american ancestry4 ,the ,virginia ,deer 7,odocoileus virginianus7 of the northern ,united ,states is a comparatively large animal1 becoming much smaller in ,florida and the ,southwest4 ,the type extends through ,mexico and ,central ,america to ,guiana and ,peru1 the ,neotropical forms being so small and having such weak antlers that they are referred to separate species4 ,another type is the ,marsh ,deer 7,blastoceros paludosus7 of eastern ,south ,america1 which has short1 stout antlers1 each beam with two double bifurcations2 there are other species of the same genus1 such as the ,pampas ,deer of ,argentina 7,b4 bezoarticus74 ,in the ,andes of ,peru and ,chili and the forests of western ,patagonia are two species of a genus which bears the preposterous name of ,hippocamelus and in which the antlers are simply forked4 ,the vernacular name of these animals is 8,huemul40 ,peculiarly ,neotropical are the little brockets1 which hardly exceed a height of two feet at the shoulder1 with simple spike-like antlers not more than three inches long2 the genus1 ,mazama1 has several species1 one of which occurs as far north as the state of ,puebla in ,mexico4 8,the smallest of all deer is the ,chilian pudu 7,pudua pudu71 a creature not much larger than a hare1 with almost rudimentary antlers0 7,lydekker74 ,old ,world types of deer1 such as the ,wapiti1 ,moose and ,caribou1 of the ,boreal and ,transition zones of ,north ,america1 are entirely absent from the ,neotropical region4 ,illustration3 ,,fig4 #ajb4--,wood ,brocket 7,mazama nemorivagus74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #ajc4--;,brazilian ,tree ,porcupine 7,coendou prehensilis74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,south ,america has an astonishingly rich and varied assemblage of rodents1 both indigenous and immigrant1 but the former are much the more important1 varied and abundant4 ,of the four divisions of the order1 all of which are represented1 three are immigrants from the north and the fourth is autochthonous1 but this far outnumbers the other three combined4 ,the hares and rabbits have but very few species1 one of which occurs in ,brazil and is separated by a very wide interval from the one in ,costa ,rica1 while the pikas are absent4 ,of the squirrel division1 only the true squirrels are found1 and of these there are many species1 the ground-squirrels1 marmots1 prairie-dogs and beavers all being lacking4 ,in the same way the rat and mouse division is represented by a single family4 ,the vesper or white-footed mice 7,sitomys7 have invaded the southern continent and a number of peculiar genera have arisen there1 but all of northern ancestry1 such as the groove-toothed mice 7,rheithrodon7 and the fish-eating rats 7,ichthyomys74 ,the voles1 or meadow-mice1 the muskrats1 jumping mice1 kangaroo-rats and pocket-gophers of the northern continent are all absent4 ,while the immigrant suborders have thus but one family each in ,south ,america1 the case is very different with the fourth or porcupine group1 of which that continent is to-day1 as it has been for ages past1 the headquarters4 ,no less than six families and twenty-nine genera are known1 all of the genera and four of the families being restricted to the ,neotropical region4 ,contrast this assemblage with the extreme scantiness of this group in ,north ,america1 where but a single genus1 the ,short-tailed or ,canada ,porcupine 7,erethizon7 represents it1 and that is a late immigrant from the south4 ,illustration3 ,,fig4 #ajd4--,neotropical rodents4 ,a4 ,vizcacha 7,viscaccia74 ,b4 ,paca 7,agouti paca74 ,c4 ,rock ,cavy 7,cavia rupestris74 ,d4 ,water-,hog1 or ,carpincho 7,hydrochrus74 ,d1 by permission of the ,n4,y4 ,zolog4 ,soc4 ,a1 ,b1 ,c1 by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #aje4--;,chinchilla 7,chinchilla laniger74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,it would lead us too far to attempt a description of this horde of curious and interesting rodents1 so only a few of the more striking and characteristic forms can be mentioned4 ,there are two genera of porcupines 7,coendou and ,chtomys71 both arboreal1 which belong in the same family as the ,north ,american ,erethizon1 but are distinguished by their long1 prehensile tails1 which they use1 as monkeys and opossums do1 for grasping and climbing4 ,the very large family of the ,octodontid has #ag ,neotropical genera and four others are found in ,africa4 ,the ,degu 7,octodon7 of ,chili1 ,bolivia and ,peru has the appearance of a large rat with tufted tail2 the tuco-tucos 7,ctenomys7 are extremely abundant burrowers in ,patagonia1 where they honeycomb the ground over wide areas4 ,the spiny rats 7,echimys and ,loncheres7 are so called from their appearance1 not because they are related to the true rats2 they have numerous horny spikes through the fur of the back4 ,the ,coypu 7,myocastor7 is a large1 aquatic animal1 remotely like the northern ,muskrat1 and the ,hutias 7,capromys and ,plagiodontia7 are arboreal and found only in ,cuba1 ,hayti and ,jamaica4 ,the chinchillas 7,chinchilla and ,lagidium7 of the ,andes and the ,vizcacha 7,viscaccia7 of the ,argentine plains have somewhat the appearance of hares1 but with long and bushy tails4 ,the cavies1 to which the familiar1 misnamed ,guinea-,pig 7,cavia porcellus7 belongs1 are a very characteristic family2 besides the true cavies1 it includes the ,patagonian ,mara 7,dolichotis71 a large1 long-legged1 long-eared1 short-tailed creature1 and the ,water-,hog1 or ,carpincho 7,hydrochrus71 an aquatic animal1 as its name implies1 and much the largest of existing rodents2 it occurs in the warmer regions1 south to ,argentina4 ,the heavy ,paca 7,agouti7 and the slender-limbed ,agouti 7,dasyprocta7 make up another family4 ,altogether1 this assemblage of the porcupine-like suborder of rodents is a very remarkable one and in no other region of the earth is anything like it to be found4 ,illustration3 ,,fig4 #ajf4--;,hairy-rumped ,agouti 7,dasyprocta prymnolopha74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,illustration3 ,,fig4 #ajg4--,three-toed ,sloth 7,bradypus tridactylus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,with the exception of one genus of armadillos1 which has invaded ,texas1 the entire order of the ,edentata is at present confined to the ,neotropical region1 the so-called edentates of the ,old ,world now being removed to other orders4 ,the ,edentata1 which were once far more varied and abundant than they now are1 comprise three groups of animals so bizarre and strange that they seem more like fabulous creatures than actual1 living mammals4 ,one group1 or suborder1 is that of the sloths 7,tardigrada71 arboreal1 shaggy animals1 with short1 almost monkey-like head and no tail2 their very long legs and hook-like feet make them nearly helpless on the ground1 but are very useful for hanging from the branches of the trees1 in which the creatures live4 ,indeed1 the sloths are the only mammals which habitually hang in a suspended position4 ,two genera of sloths inhabit the tropical forests1 between which the most obvious difference is that in one 7,bradypus7 the forefoot has three toes1 and in the other 7,cholpus7 two4 ,illustration3 ,,fig4 #ajh4--,two-toed ,sloth 7,cholpus didactylus74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,the suborder of the anteaters 7,vermilingua7 is more varied1 and is the only one of the order to which the term 8edentate0 applies strictly1 for they alone in the order are altogether toothless4 ,the great ,ant-,bear 7,myrmecophaga jubata71 which may reach a total length of seven feet1 has an extravagantly long1 slender and nearly cylindrical head1 long1 shaggy1 black and white hair and an immense1 bushy tail2 the forefeet are armed with huge1 sharp-pointed claws1 which are used for tearing open ant-hills1 and when occasion arises1 as formidable weapons of defence1 for the ,ant-,bear can successfully repulse even the ,jaguar4 ,in walking1 the claws are curved inward and the preposterous beast rests his weight upon the outside edges of the forefeet1 while the hind feet apply the sole to the ground1 as does a bear or raccoon4 ,the ,collared ,anteater 7,tamandua7 is much smaller and mainly arboreal in habits4 ,it has a short-haired1 black body1 with a white stripe down the back1 white neck and limbs1 a colour-pattern which gives to the animal the appearance of wearing a close-fitting black jacket2 the long tail1 which has some cross bars1 is short-haired1 very different from the extremely bushy tail of the ,ant-,bear4 ,the little ,two-toed ,anteater 7,cyclopes didactylus71 hardly larger than a rat1 is exclusively arboreal and has a prehensile tail1 like so many other ,south ,american mammals4 ,sloths and anteaters are forest animals and are not found west of the ,andes or south of ,paraguay4 ,illustration3 ,,fig4 #aji4--;,ant-,bear 7,myrmecophaga jubata74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #aaj4--;,collared ,anteater 7,tamandua tetradactyla74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,illustration3 ,,fig4 #aaa4--,six-banded ,armadillo 7,dasypus sexcinctus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the third existing suborder of edentates is that of the armadillos 7,dasypoda71 which have a very complete armour of bony scutes1 ossifications in the skin1 covered with scales of horn4 ,they are all more or less burrowers in habit and omnivorous in diet1 eating roots1 insects1 worms1 etc42 the extraordinary rapidity with which they burrow into the ground is almost their only way of escape from pursuit1 but in one genus1 ,tolypeutes1 the animal can roll itself into a ball1 completely protected by mail all around4 ,the armadillos are much more varied than the anteaters or sloths and have a wider geographical range1 extending from ,texas to ,patagonia4 ,the head1 which is long-snouted1 is protected by a shield made up of numerous horn-covered plates of bone1 and the tail is encased in a tubular sheath of more or less regular rings1 each ring of bony plates and horny scales4 ,the body-shield1 or carapace1 which covers the back and sides1 consists of an anterior and posterior buckler1 in which the plates are immovably attached to one another by their edges1 and between the two is a series of movable1 overlapping bands1 the number of which varies in the different genera4 ,in the little ,pichiciago 7,chlamydophorus truncatus7 the head and back are covered with four-sided plates of horn1 the bony scutes being small and thin and much reduced4 ,the carapace has no bucklers1 but about #bj transverse rows of plates1 and is attached along only the middle line of the back and beneath it the body is covered with silky1 white fur2 the rump is covered with a solid shield of bone1 placed nearly vertically and covered with thin scales1 and is notched below for the tail1 altogether a most exceptional arrangement4 ,seven or more distinct genera of armadillos are found in the ,neotropical region and they display a great range in size2 the ,giant ,armadillo of ,brazil 7,priodontes7 is a yard or more in length1 while the little ,zadyus of ,patagonia is smaller than a rabbit and1 least of all1 the ,pichiciago is but five inches long4 ,illustration3 ,,fig4 #aab4--,nine-banded ,armadillo 7,tatu novemcinctus74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,two families of marsupials occur in ,south ,america4 ,the opossums are much more numerous and varied than in ,north ,america2 three genera and a large number of species1 some not larger than mice1 range through the forested parts of the continent4 ,of particular interest is the little ,cnolestes1 which has two species1 with two enlarged lower front teeth1 the sole survivors of a group which is abundantly represented in the ,tertiary deposits of ,patagonia4 ,the fauna of the ,central ,american subregion is less rich and characteristic than that of the ,brazilian and is1 to a certain extent1 transitional to that of the ,sonoran region of ,north ,america1 several genera proper to the latter region extending into it1 which are not known to pass the ,isthmus of ,panama1 such as shrews1 a fox and one of the pocket-mice4 ,the ,west ,indian islands are exceedingly poor in mammals1 a great contrast to the ,east ,indian1 or ,malay1 ,archipelago2 only a few rodents1 insectivores and bats occur in them4 ,,chapter ,,vii ,,the ,,successive ,,mammalian ,,faunas ,,of ,,north ,,and ,,south ,,america ,the natural method of telling a story is to begin at the beginning and go on to the end1 but to deal in that manner with the many different assemblages of mammals which have in turn inhabited the western hemisphere has the great drawback of beginning with a time when everything was utterly strange to the modern eye4 ,could the reader be carried back to the far distant days of the ,paleocene epoch1 he would find himself in a completely unfamiliar world2 and there is therefore a real practical advantage in reversing the story and starting with the end and thus proceeding gradually from the more to the less familiar4 ,the foregoing chapter gave a sketch of the more striking and characteristic mammals which inhabit the ,americas to-day1 and we may now take a step backward to the epoch immediately preceding our own1 the ,pleistocene4 ,as was shown in ,chapter ,v1 the ,pleistocene was a time of many and great climatic vicissitudes1 periods of cold1 when the northern part of the continent was buried under great ice-sheets1 alternating with far milder periods1 when the climate was much as at present1 or even warmer4 ,these climatic changes necessitated many changes in the distribution of animals and plants1 increasing cold driving them southward1 while the return of more genial conditions permitted the northward migration of southern forms4 ,the effects of these changes of climate are still plainly visible in the geographical arrangement of living beings in the northern continents and many anomalies of distribution1 otherwise inexplicable1 are thus made clear4 ,attention was long ago directed to the fact that the tops of high mountains support a flora and fauna which1 on the lowlands1 will be found only hundreds1 or even thousands1 of miles to the northward4 ,the plants which grow on the summits of the ,white ,mountains of ,new ,hampshire recur in ,labrador1 but not in the intervening area2 the vegetation and animals of the high ,alps are those of the ,arctic regions1 and many similar instances might be cited4 ,hooker and ,darwin were the first to find a highly probable explanation of this curious phenomenon by referring it to the climatic changes of the ,pleistocene epoch4 ,during the last period of cold and glaciation1 the northern plants and animals were driven far to the south and occupied the lowlands along the ice-front and well beyond it2 when milder conditions gradually returned1 the northern forms not only retreated northward1 but also ascended the mountains1 as the latter were freed from ice1 and thus became cut off as isolated colonies4 ,the general explanation of 8discontinuous distribution0 7see p4 #ach7 is thus always the same1 viz41 that the intervening regions were once occupied by the forms now so widely separated1 which1 for one reason or another1 have vanished from the connecting areas4 ,i4 ,,quaternary ,,faunas ,north ,america4--,the ,quaternary faunas of ,north ,america are extremely difficult to correlate and place in chronological order1 because1 for the most part1 they are found in locally restricted areas1 such as tar-pools1 bogs1 caverns and similar places4 ,professor ,osborn has1 however1 succeeded in making an admirable arrangement1 which1 though it will doubtless be corrected and expanded by future research1 represents a most important advance4 ,of the general problem he says3 8,the study of the mammals of the ,quaternary has by no means progressed so far in ,america as in ,europe2 it will be many years before the faunistic succession can be worked out with such chronologic accuracy and precision as has at last been attained by ,european geologists and palontologists40 ,according to ,osborn's arrangement1 there are three principal successive ,pleistocene faunas1 two of which appear to have coincided with interglacial stages1 and the third with the last restablishment of glacial conditions on a grand scale4 ,regarding the details of these faunas1 there still remains much uncertainty1 and consequently there will be no attempt made here to do more than discriminate between the general ,pleistocene assemblage1 on the one hand1 and that of the last cold period1 on the other4 ,it must be emphasized that we are as yet unable to assert that all of the animals listed together were actually living at the same time4 ,it is probable that the ,pleistocene fossils already obtained give us a fairly adequate conception of the larger and more conspicuous mammals of the time1 but no doubt represent very incompletely the small and fragile forms4 ,with all its gaps1 however1 the record is very impressive2 8the early and mid-,pleistocene life of ,north ,america is the grandest and most varied assemblage of the entire ,cenozoic ,period i4e4 era of our continent0 7,osborn74 ,there is the further advantage that the fossils have been gathered over a very great area1 extending from ocean to ocean and from ,alaska to ,central ,america4 ,thus1 their wide geographical range represents nearly all parts of the continent and gives us information concerning the mammals of the great forests1 as well as of the great plains4 ,those divisions of the early and middle ,pleistocene which enjoyed milder climatic conditions had an assemblage of mammals which1 from one point of view1 seems very modern1 for most of the genera1 and even many of the species1 which now inhabit ,north ,america1 date back to that time4 ,from the geographical standpoint1 however1 this is a very strange fauna1 for it contains so many animals now utterly foreign to ,north ,america1 to find near relatives of which we should have to go to ,asia or ,south ,america4 ,some of these animals which now seem so exotic1 such as the llamas1 camels and horses1 were yet truly indigenous and were derived from a long line of ancestors which dwelt in this continent1 but are now scattered abroad and extinct in their original home1 while others were migrants that for some unknown reason failed to maintain themselves4 ,others again are everywhere extinct4 ,illustration3 ,,fig4 #aac4--,some of the more characteristic ,pleistocene mammals1 reduced to a uniform scale1 with a pointer dog 7in the frame7 to show relative sizes4--#a4 ,columbian ,elephant 7,elephas columbi74 #b4 ,giant ,ground-,sloth 7,megalonyx jeffersoni74 #c4 ,stag-,moose 7,cervalces scotti74 #d4 ,american ,mastodon 7,mastodon americanus74 #e4 ,giant ,beaver 7,castoroides ohioensis74 #f4 ,texas ,horse 7,equus scotti74 #g4 ,sabre-tooth ,tiger 7,smilodon californicus74 ,most surprising1 perhaps1 in a ,north ,american landscape1 is the presence of the ,proboscidea1 of which two very distinct kinds1 the mastodons and the true elephants1 are found together4 ,over nearly the whole of the ,united ,states and southern ,canada1 and even with sporadic occurrence in ,alaska1 ranged the ,american ,mastodon 7,mastodon americanus7 which was rare in the plains1 but very abundant in the forested regions1 where it persisted till a very late period and was probably known to the early ,indians4 ,this animal1 while nearly related to the true elephants1 was yet quite different from them in appearance1 as will be immediately seen on comparing #a and #d1 ,fig4 #aac1 p4 #aie4 ,the most obvious external difference was the comparative shortness of the legs in the ,mastodon1 which did not exceed and seldom attained a height of #i ft4 #f in4 at the shoulder2 the head also was lower and more flattened4 ,the teeth were very different from those of the elephants2 the grinding teeth were much smaller and simpler1 being low-crowned and rooted and having three or four high1 transverse1 enamel-covered crests1 without cement4 ,the tusks were elephant-like except that in the male there was a single small tusk in the lower jaw1 which cannot have been visible externally2 this is a remnant of an earlier stage of development1 when there were two large tusks in the lower as well as the upper jaw4 ,the creature was covered with long1 coarse1 dun-coloured hair2 such hair has been found with some of the skeletons4 ,of true elephants1 the ,north ,american ,pleistocene had three species4 ,most interesting of these is the northern or ,siberian ,mammoth 7,elephas primigenius71 a late immigrant from northern ,asia1 which came in by way of ,alaska1 where ,bering ,land 7as we may call the raised bed of ,bering ,sea7 connected it with ,asia4 ,the ,mammoth was abundant in ,alaska1 ,british ,columbia and all across the northern ,united ,states to the ,atlantic coast4 ,hardly any fossil mammal is so well known as this1 for the carcasses entombed in the frozen gravels of northern ,siberia have preserved every detail of structure4 ,it is thus definitely known that the ,mammoth was well adapted to a cold climate and was covered with a dense coat of wool beneath an outer coating of long1 coarse hair1 while the contents of the stomach and the partially masticated food found in the mouth show that the animal fed upon the same vegetation as grows in northern ,siberia to-day4 ,the grinding teeth were very high1 cement-covered1 and composed of many thin plates of enamel1 dentine and cement1 and were closely similar to those of the existing ,indian ,elephant 7,e4 maximus74 ,in size this is the smallest of the three ,pleistocene species1 #i feet at the shoulder4 ,the ,mammoth was not peculiar to ,siberia and ,north ,america1 but extended also into ,europe1 where it was familiar to ,palolithic ,man1 as is attested by the spirited and lifelike carvings and cave-paintings of that date4 ,thus1 during some part of the ,pleistocene1 this species ranged around the entire northern hemisphere4 ,closely related to the ,mammoth and in some cases hardly distinguishable from it1 is the ,columbian ,elephant 7,e4 columbi7 which1 however1 attained a considerably larger size1 as much as #aa feet1 rivalling the largest ,african elephants of the present time4 ,the head was very high and had a curiously peaked appearance1 and the tusks in old males curved inward1 overlapping at the tips4 ,from the likeness in teeth and skeleton to the ,mammoth1 it may be inferred1 though somewhat doubtfully1 that the ,columbian ,elephant was clothed with hair1 but not so heavily as the ,mammoth1 which was a northern species1 the ,columbian form replacing it southward1 and ranging over the whole ,united ,states1 including ,florida and even throughout the table-land of ,mexico4 ,the areas of the two species overlapped along the northernmost ,united ,states1 but are elsewhere distinct4 ,illustration3 ,,fig4 #aad4--,restoration of the ,columbian ,elephant 7,elephas columbi7 from a skeleton in the ,american ,museum of ,natural ,history4 ,a third species was the huge ,imperial ,elephant 7,e4 imperator71 the largest of ,american forms1 to which ,osborn's calculations give the almost incredible height of #ac ft4 #f in4 ,this great creature was characterized not only by its enormous stature1 but also by the proportionately very large size of its grinding teeth1 and was a survivor from the preceding ,pliocene epoch2 it is not known to have passed beyond the middle ,pleistocene and was thus the first of the species to become extinct4 ,in geographical range1 the ,imperial ,elephant was a western form1 extending from the ,pacific coast almost to the ,mississippi ,river1 east of which it has never been found1 and from ,nebraska southward to the ,city of ,mexico4 ,the meaning of this distribution is probably that this elephant shunned the forests and was especially adapted to a life on the open plains4 ,over most of its area the winters were severe1 and this fact makes it likely that the animal was clothed with hair1 but nothing is definitely known on this point4 ,illustration3 ,,fig4 #aae4--;,a ,horse 7,equus scotti7 from the older ,pleistocene of ,texas4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,many other hoofed animals1 far more than now inhabit ,north ,america1 are found in this ,pleistocene fauna4 ,the ,perissodactyla were represented by horses and tapirs1 but not by rhinoceroses2 it might seem superfluous to say that there were no rhinoceroses1 but1 as a matter of fact1 that family had a long and varied ,american history and became extinct only during or at the end of the ,pliocene epoch4 ,the horses were extremely numerous1 both individually and specifically1 and ranged1 apparently in great herds1 all over ,mexico and the ,united ,states and even into ,alaska4 ,all the known species 7at least ten in number7 belong to the genus ,equus1 but the ,true ,horse 7,e4 caballus71 to which all the domestic breeds are referred1 is not represented4 ,the smallest known member of the genus is the pygmy ,e4 tau of ,mexico4 ,e4 fraternus1 likewise a very small species1 is found especially in the southeast1 but extended as far north as ,pennsylvania and west to ,nebraska4 ,on the other hand1 ,e4 giganteus of ,texas exceeded the heaviest modern draught-horses in size and was the largest of the ,american species2 of other ,texan forms1 one 7,e4 scotti7 resembled ,burchell's ,zebra 7,e4 burchelli7 in the proportions of head and neck1 body and limbs1 while another 7,e4 semiplicatus7 was more ass-like4 ,the forest horse of the eastern states has been named ,e4 pectinatus1 an animal of moderate size4 ,the ,great ,plains must have been fairly covered with enormous herds of horses1 the countless bones and teeth of which1 entombed in the ,sheridan formation1 have given to it the name of 8,equus beds40 ,the most abundant of the plains species is ,e4 complicatus1 a horse of about #ad hands in height 7i4e4 #d feet #aj inches at the shoulder7 which also ranged down the ,mississippi ,valley nearly or quite to the ,gulf of ,mexico4 ,in ,california was ,e4 occidentalis1 equalling ,e4 complicatus in size1 but with much more simple teeth1 and associated with it the much larger ,e4 pacificus1 which was inferior only to ,e4 giganteus and therefore the second largest of the ,american ,pleistocene horses4 ,to one who knows nothing of the geological history of ,north ,america it would be natural to suppose that the ,pleistocene horses must have been immigrants from the ,old ,world1 which failed to establish themselves permanently here1 since they completely disappeared before the discovery of the continent by ,europeans4 ,this would1 however1 be a mistaken inference1 for ,north ,america was for long ages the chief area of development of the equine family1 which may here be traced in almost unbroken continuity from the lower ,eocene to the ,pliocene4 ,on the other hand1 it is quite possible that some of the species were immigrants4 ,tapirs1 which are now confined to southern ,asia1 ,central and ,south ,america1 were not uncommon in the forested parts of eastern ,north ,america as far north as ,pennsylvania1 but they have not been found west of the ,mississippi in the plains region4 ,two species are known1 a larger and heavier one1 ,tapirus haysii1 and a smaller one which seems to be identical with the living ,t4 terrestris of ,central and ,south ,america4 ,like the horses1 the tapirs had a long history of development in ,north ,america and may well have originated here1 but they withdrew from the continent in the ,pleistocene1 probably yielding to the last of the glacial advances4 ,there was likewise a much greater variety of ,artiodactyla than ,north ,america can boast at the present day2 some were autochthonous1 but1 for the most part1 they were migrants from the eastern hemisphere1 where the great group of the true ruminants 7,pecora7 passed through the greater part of its development and where its headquarters still are4 ,indigenous were the peccaries1 or ,american swine1 which still occur from ,texas south to ,brazil4 ,in ,pleistocene time they ranged over nearly all of the ,united ,states1 as far northward as ,pennsylvania1 and across the plains to the ,pacific coast2 they were represented by two genera1 now extinct1 one of which 7,platygonus7 had crested grinding teeth and much longer legs than the modern peccaries4 ,another indigenous group1 strange as that may seem1 is the suborder 7,tylopoda7 of the camels and llamas1 both of which are represented in the ,north ,american ,pleistocene1 the descendants of a very long ,american ancestry4 ,some of these tylopodans were far larger than existing forms1 and at least one species extended its range to ,alaska4 ,of ultimately ,old ,world origin1 but through a considerable line of descent in ,america1 were the typically ,american deer 7,odocoileus7 of which the ,virginian and ,black-tailed species are familiar modern instances4 ,whether or not the ,old ,world types1 the ,caribou 7,rangifer7 and ,wapiti 7,cervus canadensis7 had reached the western hemisphere1 is a matter of some doubt2 if present at all1 they must have been comparatively rare4 ,the ,moose 7,alce americanus71 on the other hand1 had already appeared1 but seems to have been confined to the western half of the continent1 its presence in the east being questionable4 ,the mistakenly named 8,rocky ,mountain ,goat0 7,oreamnos montanus71 which is an antelope of the chamois group1 was an apparently late arrival in the ,pleistocene1 while the peculiar ,prong-,buck 7,antilocapra americana71 which is very different from any of the ,old ,world antelopes1 was present in the early part of the epoch4 ,the descent of this remarkable animal is still a problem1 but not improbably it was derived from the 8deer-antelopes0 of the ,miocene and ,pliocene1 the last of which occurred in the early ,pleistocene4 ,mr4 ,gidley has announced the surprising discovery in ,maryland of a large antelope hardly distinguishable from the ,african ,eland 7,taurotragus74 ,other late arrivals from the ,old ,world were several forms allied to the existing ,musk ,ox 7,ovibos71 at least two genera of which 7,preptoceras and ,euceratherium7 have been found in ,california4 ,a surprising number of species of ,bison occurred in the ,pleistocene1 no less than seven of which are recognized as distinct1 ranging from ,florida to ,alaska4 ,it is not likely that all these species coexisted at the same time1 but we cannot yet determine their order of succession1 though the modern species1 ,b4 bison1 was probably the latest to arise4 ,most of these species were much larger than ,b4 bison1 and some were gigantic1 such as ,b4 latifrons1 which had a spread of horns of #f feet and is found through the ,mississippi ,valley1 and ,b4 crassicornis of ,alaska4 ,illustration3 ,,fig4 #aaf4--,restoration of ,preptoceras1 a musk-ox like animal from the ,californian ,pleistocene4 7,from a skeleton in the museum of the ,university of ,california47 ,preying upon this great assemblage of hoofed animals was a corresponding array of ,carnivora1 most of which were indigenous and derived from ,american stocks1 but there was a considerable migrant element also1 such as the bears and badgers4 ,nearly all the modern kinds of flesh-eaters found in the ,north ,america of to-day were already here in the ,pleistocene1 minks1 weasels1 martens1 skunks1 otters1 badgers1 wolverenes1 raccoons1 foxes1 wolves1 coyotes1 pumas1 etc41 etc41 but there were several others which are either now extinct or no longer to be found in this continent4 ,of the extinct types much the most striking were the several species of sabre-tooth tigers 7,smilodon1 see ,frontispiece7 which have been found in the greater part of the ,united ,states and no doubt ranged over the whole4 ,these were massive1 short-tailed and rather short-legged1 but very muscular and powerful1 cat-like animals1 in which the upper canine teeth were converted into great1 recurved1 scimitar-like tusks4 ,these large beasts of prey1 which about equalled the ,leopard in height1 but were far heavier1 belonged to a group which1 at one time or another1 spread over nearly the whole world and persisted much later and attained a larger size and higher development in the western hemisphere than in the eastern4 ,they had a very long ,american ancestry1 from the lower ,oligocene to the end of the ,pleistocene1 but the place of their origin is still unknown4 ,in addition to the pumas and lynxes1 there were some very large true felines 7,felis atrox and ,f4 imperialis71 which closely resembled the ,lion 7,f4 leo7 in size1 appearance and structure1 and have been found in ,california and the ,mississippi ,valley2 probably these great cats were immigrants1 but they may represent a native development of ,miocene and ,pliocene stock2 the history of the family is too imperfect for a decision of this question4 ,besides coyotes and wolves which are indistinguishable from existing species1 there were some very large wolves1 now extinct1 of which the commonest and most widely distributed was ,canis dirus 7also called ,c4 indianensis7 so abundant in the asphalts of southern ,california4 ,bears were not so common in the middle ,pleistocene and have not been found in the older part of that epoch1 though they probably had already reached ,north ,america from the ,old ,world1 where they originated4 ,their absence from the older ,pleistocene 7,equus ,beds7 may be accounted for by the fact that those beds contain a fauna of the open plains1 while bears are chiefly forest-living animals4 ,an extinct type of the family is the group of species which constitute the short-faced bears 7,arctotherium71 very large and powerful creatures1 with remarkably shortened jaws1 which have been found from ocean to ocean4 ,the smaller beasts of prey1 badgers1 weasels1 etc41 were1 as intimated above1 substantially the same as now4 ,the rodents of the ,pleistocene were very nearly in their modern stage of development1 most of the genera and many of the species surviving to present times4 ,just what members of the order were introduced from the ,old ,world1 the imperfect and fragmentary history will not permit us to say1 but some interesting ,south ,american immigrants should be noted4 ,one of these1 the ,capybara or so-called ,water-,hog 7,hydrochrus capybara71 the largest of existing rodents1 failed to gain a permanent foothold1 but another ,south ,american form1 the ,short-tailed or ,canada ,porcupine 7,erethizon dorsatus71 common all over the ,united ,states in the ,pleistocene1 has maintained itself to the present day4 ,one especially peculiar form1 not derived from ,south ,america or the ,old ,world1 is the ,giant ,beaver 7,castoroides71 one species of which1 ,c4 ohioensis1 was as large as a ,black ,bear and occurred in the later ,pleistocene1 while a smaller species 7,c4 species indet47 is found in the more ancient deposits of the epoch4 ,in almost all respects ,castoroides was simply a gigantic beaver1 but the grinding teeth were remarkably like those of the ,south ,american ,capybara 7,hydrochrus71 so much so that it has been mistakenly referred to the same family by some authorities4 ,by far the strangest elements of the ,pleistocene faunas were the two suborders of gigantic edentates1 the ,gravigrada1 or ground-sloths1 and the ,glyptodontia1 which might well be called giant armadillos1 if that name were not already in use for a living ,brazilian animal4 ,both suborders are completely extinct1 but they long played a very conspicuous rle in ,south ,america1 where they originated and whence the ,north ,american representatives migrated4 ,the ground-sloths were great1 unwieldy1 herbivorous animals covered with long hair1 and in one family 7,mylodontid7 there was a close-set armour of pebble-like ossicles in the skin1 not visible externally2 they walked upon the outer edges of the feet1 somewhat as the ,ant-,bear 7,myrmecophaga7 uses his fore paws1 and must have been very slow-moving creatures4 ,their enormous claws may have served partly as weapons of defence and were doubtless used also to drag down branches of trees and to dig roots and tubers4 ,apparently1 the latest of these curious animals to survive was the very large ,megalonyx1 which1 it is interesting to note1 was first discovered and named by ,thomas ,jefferson4 ,the animals of this genus were very abundant in the forests east of the ,mississippi ,river and on the ,pacific coast1 much less common in the plains region1 where they would seem to have been confined to the wooded river valleys4 ,the still more gigantic ,megatherium1 which had a body as large as that of an elephant and much shorter1 though more massive legs1 was a southern animal and has not been found above ,south ,carolina4 ,mylodon1 smaller and lighter than the preceding genera1 would seem to have entered the continent earlier and to have become extinct sooner2 it ranged across the continent1 but was much commoner in the plains region and less so in the forested areas than ,megalonyx1 being no doubt better adapted to subsisting upon the vegetation of the plains and less dependent upon trees for food4 ,the ,glyptodonts were undoubtedly present in the ,north ,american ,pleistocene1 but the remains which have been collected so far are very fragmentary and quite insufficient to give us a definite conception of the number and variety of them4 ,it will be better therefore to defer the description of these most curious creatures until the ,south ,american ,pleistocene is dealt with1 as they were incomparably more varied and characteristic in that continent4 ,in ,north ,america they have been found only in ,mexico and the southern ,united ,states4 ,the many and great climatic changes which took place in the ,pleistocene led to very extensive migrations of mammals from one part of the continent to another1 as the conditions of temperature and moisture changed4 ,in ,interglacial stages1 when the climate was much ameliorated1 southern species spread far to the north1 as when the ,mastodon ranged into ,alaska1 and the ,manatee1 or ,sea-,cow1 of ,florida waters1 came up the coast to ,new ,jersey1 while the increasing cold of oncoming glaciation caused a reverse movement and drove northern and even ,arctic forms far to the south4 ,thus1 the ,musk-,ox1 the ,caribou and the northern ,mammoth came south beyond the ,ohio and the ,potomac1 and the ,walrus was found on the ,south ,atlantic coast4 ,it is these migrations which give such a mixed character to the ,pleistocene faunas from the climatic point of view1 as it is often very difficult to correlate or synchronize the fossiliferous deposits with the ,glacial and ,interglacial stages1 though this has been definitely accomplished in several very important instances4 ,the latest of the ,pleistocene faunas is less completely known than those of the earlier and middle portions of the epoch1 for but few localities have yet been discovered with any extensive series of fossils4 ,as worked out by ,osborn1 this fauna coincided with the last ,glacial stage and was a greatly reduced and impoverished assemblage as compared with those of the middle and lower ,pleistocene1 though it is not safe to argue that all the animals not found in this fauna were already extinct1 for the known list is still far too short to be entirely representative4 ,the ,american ,mastodon 7,mastodon americanus1 see p4 #aif7 was still abundant in the forested regions and was apparently able to withstand severe winter temperatures1 as certainly was the ,mammoth 7,elephas primigenius1 see p4 #aif71 which was so abundant in the coldest part of ,siberia and which extended south to the ,potomac1 presumably at this time4 ,horses were still present in ,north ,america1 though apparently in greatly diminished numbers and variety4 ,tapirs have not been found1 though they may have lingered on in the southern regions4 ,the typically ,north ,american genus of deer 7,odocoileus7 was1 of course1 well represented1 and ,old ,world types had a much more southerly distribution than at present4 ,the ,caribou 7,rangifer caribou7 came down into ,pennsylvania and ,ohio1 the ,moose 7,alce americanus7 into ,kentucky and ,kansas1 and the ,wapiti 7,cervus canadensis7 is reported as far south as ,florida4 ,a very remarkable animal is the ,stag-,moose 7,cervalces scotti71 the best preserved skeleton of which is that in the museum of ,princeton ,university4 ,this was found in a shell-marl beneath a peat-bog at ,mt4 ,hermon1 ,n4 ,j41 north of the great terminal moraine1 and therefore most probably this particular individual dates from a time not earlier than the beginning of the final retreat of the ice4 ,cervalces1 as its name implies1 was in some respects intermediate between the ,stag 7,cervus7 and the ,moose 7,alce72 in general proportions it most nearly resembled the latter1 having a short neck1 long body and very long legs2 but the skull differed in many respects from that of the ,moose1 especially in parts which show that the great1 inflated snout and prehensile upper lip had no such development in the extinct as in the living form4 ,the antlers were unique among the known members of the deer family1 resembling those of the ,moose1 though much less palmated and with the addition of great trumpet-shaped plates4 ,the feet were large1 almost as large as in the ,caribou1 and the whole structure indicates an animal well fitted to travel through deep snows and flourish in severe winters4 ,illustration3 ,,fig4 #aag4--;,cervalces scotti3 restored from a skeleton in the museum of ,princeton ,university4 ,even more typically northern than the ,caribou were the ,musk-,oxen1 of which two genera occurred in the late ,pleistocene4 ,one of these1 ,symbos1 is extinct and was characterized by its short horns2 the other1 ,ovibos1 is the genus to which the existing species1 ,o4 moschatus and ,o4 wardi1 belong and is now confined to the extreme north of the continent1 the ,arctic islands and ,greenland4 ,the remains of ,musk-,oxen have been found mostly along the great terminal moraine which marks the front of the last ice-invasion1 but they occurred also as far south as ,oklahoma1 and in ,utah they ranged far to the south of the ice-front4 ,nothing could be more conclusive evidence of a climate much colder than the modern one than the presence of ,caribou and ,musk-,oxen in the ,united ,states and of the ,walrus on the coast of ,georgia4 ,the smaller animals were much as they are now1 differing only in range4 ,the sabre-tooth tigers1 the last of a most interesting line1 persisted in the south1 and an extinct genus of skunks has been discovered in ,arkansas1 but otherwise the ,carnivora were entirely modern in character4 ,unfortunately1 these smaller animals are very incompletely known1 much the richest aggregation which has yet been found being that collected by ,mr4 ,brown in the ,conard ,fissure1 ,arkansas4 ,from this collection ,mr4 ,brown has described thirty-seven genera and fifty-one species of mammals1 of which four genera and twenty-four species are extinct4 ,that is to say1 less than one-ninth of the genera and one-half of the species represent extinct forms4 ,contrast this with the middle ,pleistocene assemblage found in the ,port ,kennedy cavern in eastern ,pennsylvania1 of sixty-four species with at least forty extinct ones4 ,the foregoing sketch1 brief and imperfect as it necessarily is1 makes it sufficiently plain that ,north ,america during the ,pleistocene was far richer in mammalian life than it was when the continent was first settled by ,europeans4 ,when we make the proper allowance for the many forms which undoubtedly remain to be discovered and for those which may have vanished without leaving a trace behind them1 the contrast becomes all the more striking4 ,not only did ,pleistocene ,north ,america have substantially all the mammals that it now possesses1 but it had many more4 ,the lions and sabre-tooth tigers1 the gigantic short-faced bears1 the tapirs and many varieties of horses1 large and small1 the camels and llamas1 many species of bisons1 some of enormous proportions1 several forms allied to the ,musk-,ox1 the elephants and mastodons1 the giant beavers and ,south ,american water-hogs1 the huge ground-sloths and glyptodonts1 have all disappeared1 leaving a continent1 that1 by contrast1 is 8zologically impoverished40 ,the ,pleistocene fauna was strangely mixed in character1 the free roads of migration bringing together ,old ,world and ,south ,american types1 and mingling them with indigenous forms in a cosmopolitan assemblage4 ,turning to ,south ,america1 we find in the pampas of ,argentina a wonderful museum of ,pleistocene mammals1 such as occurs nowhere else in the known world1 and this is supplemented by the very rich collections gathered from the caverns of ,brazil and from deposits of ,ecuador and ,bolivia1 and thus all the important regions of the continent1 save the far south1 are well represented4 ,these faunas are far stranger than the corresponding ones of ,north ,america and differ more radically from those of modern times1 since they include a much larger proportion of extinct types1 and the extinctions have swept away not only species and genera1 but families and orders as well4 ,the ,south ,american ,pleistocene assemblage of mammals is very clearly divisible into two elements3 7#a7 the immigrants from the north1 which reached the southern continent in successive waves of migration1 that have left records of themselves as early as the older ,pliocene1 perhaps even the upper ,miocene1 and 7#b7 the indigenous element1 which had a very long history of development in ,south ,america4 ,to the immigrant class belonged all of the ,carnivora1 which therefore resembled their ,north ,american relatives1 but were less varied in character4 ,of the bears1 only the huge1 short-faced kind 7,arctotherium1 ,fig4 #bge1 p4 #edi7 are known1 and it is not likely that true bears existed except in the ,andes1 as is also the case to-day4 ,of the cat family1 the sabre-tooth tigers 7,smilodon7 were as common in ,south ,america as in ,north1 and1 while there were no lions1 there were large cats nearly allied to the ,jaguar and ,puma1 and smaller ones1 like the ,ocelot4 ,the dogs were quite numerously represented by species resembling closely the existing ,south ,american fox-like wolves and the ,bush-,dog 7,icticyon7 and1 strange to say1 by one which seems referable to the same genus 7,cyon7 as the ,dhole of ,india4 ,the weasel family 7,mustelid7 were less numerous and varied than in the northern continent1 as they still are2 coatis 7,nasua7 and raccoons 7,procyon7 were abundant and one species of the latter was much larger than any existing one2 extinct species of skunk 7,conepatus71 tayra 7,tayra7 and otter 7,lutra7 were also present1 but the badgers1 minks1 martens and wolverenes were not4 ,illustration3 ,,fig4 #aah4--,some of the commoner ,pampean mammals1 reduced to a uniform scale1 with a pointer dog 7in the frame7 to show the relative sizes4 #a4 ,ddicurus clavicaudatus4 #b4 ,glyptodon clavipes1 glyptodonts4 #c4 ,macrauchenia patachonica1 one of the ,litopterna4 #d4 ,pampas ,horse 7,hippidion neogum74 #e4 ,toxodon burmeisteri1 a toxodont4 #f4 ,megatherium americanum4 #g4 ,mylodon robustus1 ground-sloths4 ,the hoofed animals were represented by a great variety of forms1 both immigrant and indigenous1 of which the latter belonged to orders now entirely extinct4 ,horses were common in all parts of the continent1 where fossils of this epoch have been obtained1 and are referable to two very distinct groups3 7#a7 to the typical genus ,equus1 of which three species have been described1 all somewhat more primitive than the ,true ,horse 7,e4 caballus7 and1 like most of the ,pleistocene species of ,north ,america1 with a certain resemblance to the zebras and asses2 7#b7 to an extinct group of four genera1 the best known of which is ,hippidion4 ,the species of this genus 7which has also been reported from ,north ,america1 though upon hardly sufficient evidence7 had most exceptional characters in the skull1 and the head was relatively large and clumsy1 with narrow and very high facial region4 ,the neck was comparatively short1 the limbs heavy and the feet short4 ,these animals can hardly have been very swift runners4 ,a very interesting member of this group is ,hyperhippidium1 a small horse found in the ,andes1 with remarkably short feet1 well adapted for a mountain life4 ,the only other perissodactyls were tapirs1 which ranged down to the ,argentine pampas1 much farther south than now4 ,illustration3 ,,fig4 #aai4--;,a ,pampas ,horse 7,hippidion neogum74 ,restored from a skeleton in the ,national ,museum1 ,buenos ,aires4 ,the ,artiodactyla were much more varied2 there were peccaries1 many species of llamas1 which then extended into ,brazil1 and were not confined1 as at present1 to the colder portions of the continent4 ,there were also numerous deer1 all of the ,south ,american type1 and two different antelopes have been reported1 though that family has no representatives in the southern continent now4 ,several species of mastodons have been found in ,brazil1 ,argentina1 ,bolivia and elsewhere1 but none of the true elephants4 ,why the mastodons were able to make their way into ,south ,america1 while the elephants were not1 is one of the puzzling questions of mammalian distribution to which no answer can be given4 ,all the preceding types of hoofed animals1 the horses1 tapirs1 peccaries1 llamas1 deer1 antelopes and mastodons were migrants from the north1 and four of these1 tapirs1 peccaries1 llamas and deer1 were able to gain a permanent footing in ,south ,america and are more or less abundant there to-day1 while the horses1 antelopes and mastodons failed to do so and died out4 ,in addition to these1 there were the indigenous types1 which are now extinct and have never been found outside of the ,neotropical region4 ,an extremely peculiar creature1 ,macrauchenia1 was the last surviving member of an order1 the ,litopterna1 which for ages played a very important rle in ,south ,america4 ,macrauchenia was a large animal1 somewhat larger and of much heavier build than a camel1 to which it had a considerable1 though entirely superficial1 resemblance4 ,the head was relatively small and must have had quite a long proboscis2 the neck was very long1 suggesting that the animal browsed upon trees1 which is also indicated by the character of the teeth2 the legs were long and stout1 the feet short and each provided with three toes4 ,another curious creature was ,typotherium1 from which is named the group of the ,typotheria1 which some authorities regard as a suborder1 while others assign to it a full ordinal rank4 ,illustration3 ,,fig4 #abj4--;,a ,pampean ,litoptern 7,macrauchenia patachonica74 ,restored from a skeleton in the ,museum of ,la ,plata4 ,the ,typotheres throughout the ,tertiary period were among the most abundant and characteristic of the ,south ,american hoofed animals1 and the genus ,typotherium was the last of a very long series and was an animal of moderate size1 with chisel-shaped incisor teeth so like those of the rodents that the genus was long referred to that order4 ,finally1 we have ,toxodon1 type of the order ,toxodontia1 a ponderous beast1 as large as a rhinoceros1 which1 there is some reason to think1 was largely aquatic in its habits4 ,the first species of this extraordinary creature was found by ,charles ,darwin1 who says of it3 8,perhaps one of the strangest animals ever discovered2 in size it equalled an elephant or megatherium1 but the structure of its teeth1 as ,mr4 ,owen states1 proves indisputably that it was intimately related to the ,gnawers i4e4 ,rodentia 444 in many details it is allied to the ,pachydermata3 judging from the position of its eyes1 ears1 and nostrils1 it was probably aquatic1 like the ,dugong and ,manatee1 to which it is also allied40#d ,modern views concerning the relationships of ,toxodon are very different from those advanced by ,darwin1 but he gives a vivid picture of its diverse likenesses4 ,neither ,macrauchenia1 ,typotherium nor ,toxodon has been found in the ,brazilian caverns1 but this is no doubt due to the accidents of preservation1 for the latter animal ranged north to ,nicaragua4 ,illustration3 ,,fig4 #aba4--;,a ,pampean ,toxodont 7,toxodon burmeisteri74 ,restored from a skeleton in the ,la ,plata ,museum4 ,the rodents likewise were partially of immigrant and partially of native stock4 ,to the former belonged the few mice and rats and a meadow-mouse 7,microtus71 a group not represented in present-day ,south ,america1 and a rabbit4 ,very much more abundant and varied were the indigenous forms1 all of which belonged to existing families and most of them to existing genera2 the tree-porcupines1 cavies1 agoutis1 spiny-rats1 vizcachas1 capybaras1 coypus1 etc41 were abundantly represented1 for the most part by extinct species4 ,the monkeys were of purely ,neotropical type and several modern genera1 such as ,cebus and ,callithrix1 and one very large extinct genus1 ,protopithecus1 of the same family1 have been found in the caverns of ,brazil1 but not in the pampas of ,argentina1 which would seem to have been a country of open plains4 ,in the ,south ,america of to-day one of the most striking and peculiar elements of the fauna is that formed by the ,edentata1 the sloths1 anteaters and armadillos1 and this was even more true of the same region in ,pleistocene times4 ,anteaters and sloths are very scantily represented1 but this is merely an accident of preservation2 armadillos1 on the other hand1 were very numerous both in ,brazil and in ,argentina1 and1 in addition to many modern genera1 there were several which are no longer in existence1 such as ,chlamydotherium1 which was a huge creature almost as large as a rhinoceros4 ,then there were the two extinct suborders of the glyptodonts 7,glyptodontia7 and the ground-sloths 7,gravigrada7 which were astonishingly abundant in ,argentina and which1 as was shown in a previous page 7p4 #bje71 were also well represented in ,north ,america4 ,few more fantastic-looking mammals than the glyptodonts have ever been found2 the short1 deep head1 with its shield of thick1 bony plates1 the huge carapace made up of innumerable plates of bone firmly united at their edges and without the movable bands of the armadillo carapace1 the enormous tail-sheath1 the short legs and massive feet with broad hoofs1 must have given these animals rather the appearance of gigantic tortoises than of mammals4 ,the glyptodonts were especially numerous and varied in the ,argentine pampas1 and a stately array of them is mounted in the museums of ,la ,plata and ,buenos ,aires2 in length1 they ranged from six to twelve feet1 including the tail4 ,the skeleton and carapace did not differ very greatly in appearance among the various genera1 but there were great differences in the form and size of the bony sheath enclosing the tail4 ,in the genus ,glyptodon the sheath was composed throughout of movable overlapping rings1 with prominent spines on them2 in ,sclerocalyptus the hinder half of the sheath coalesced into a single piece1 marked only by the elaborate ornamentation of the horny scales1 while in ,ddicurus the end had a tremendous1 club-like expansion1 which must have been set with great horn-like spines4 ,the glyptodonts were ponderous1 slow-moving and inoffensive plant-feeders1 almost invulnerable to attack1 and probably used their massive tails1 which could be freely swung from side to side1 as redoubtable weapons of defence1 much as the alligator uses his tail4 ,in comparison with the bewildering variety in ,south ,america1 the few that made their way into ,north ,america were quite insignificant4 ,much the same statement applies to the ground-sloths1 and though these ranged far more widely through the northern continent than did the glyptodonts1 they were but few in comparison with the multitude which inhabited alike the forests of ,brazil and the plains of the south4 ,two of the three genera of ground-sloths which occur in the ,north ,american ,pleistocene1 ,megatherium and ,mylodon1 are also found in ,south ,america2 and though ,megalonyx has not yet been obtained there1 the family of which it is a member was represented4 ,in size1 these creatures varied from a tapir to an elephant1 though all were much shorter-legged than any elephant2 the extremely massive tail1 which the larger forms had1 served to support the huge body1 when erected to tear down the branches and leaves upon which these strange creatures fed4 ,illustration3 ,,fig4 #abb4--;,a gigantic ,pampean ,ground-,sloth 7,megatherium americanum74 ,restored from a skeleton in the ,museum of ,la ,plata4 ,opossums were extremely numerous1 especially in the ,brazilian caves1 where in half a cubic foot of earth #djj jaws were collected4 ,the ,pleistocene mammalian fauna of ,south ,america was a mixture of modern forms with ancient1 vanished types similar to that which we found in ,north ,america4 ,the ground-sloths and glyptodonts1 the litopterns1 toxodonts and typotheres1 the antelopes1 horses and mastodons have all disappeared from the continent1 or vanished altogether from the face of the earth4 ,,ii4 ,,tertiary ,,faunas #a4 ,pliocene ,north ,america4--,no part of the ,cenozoic history of ,north ,america is so imperfectly recorded and so unsatisfactorily known as that of the ,pliocene1 and the later portion of that epoch is especially obscure4 ,if the ,peace ,creek formation of ,florida is properly referred to the upper ,pliocene1 it would show that the mammals of that time were substantially the same as those of the early ,pleistocene4 ,the only fauna1 as yet discovered1 which can be referred to the middle ,pliocene1 is that of the ,blanco beds of northwestern ,texas1 which have yielded but a scanty list of mostly ill-preserved fossils4 ,obviously1 these give us a very incomplete picture of the life of that time4 ,the great ground-sloths had already reached ,north ,america1 and the genus ,megalonyx1 so common in the forested areas of ,pleistocene ,north ,america1 was perhaps already in existence4 ,the glyptodonts were likewise represented by one genus 7,glyptotherium7 which was distinguished by the simple rings of the tail-sheath4 ,no rodents have yet been found and only a few of the ,carnivora1 though a large cat1 a musteline and a large 8bear-dog0 are known4 ,there were no true elephants1 but several species of mastodons1 all of which were different from those of the ,pleistocene2 and in some1 grinding teeth1 though still low-crowned1 had become much larger and more complex1 marking a stage of advance toward the elephantine dentition4 ,horses of primitive type1 the feet having three functional toes instead of one1 were relatively abundant4 ,very large llama-like animals were present1 but nothing has been ascertained with regard to the deer and antelopes of the time1 and the only other representative of the ,artiodactyla yet recovered is a peccary1 interesting as being a species of the genus 7,platygonus7 which became so abundant and widespread in the ,pleistocene4 ,scanty and incomplete as this fauna is1 it suffices to show that the middle ,pliocene mammals were much more primitive than those of the ,pleistocene4 ,illustration3 ,,fig4 #abc4--;,horned ,gopher 7,epigaulus hatcheri71 lower ,pliocene1 ,nebraska4 ,restored from a skeleton in the ,u4,s4 ,national ,museum4 ,the fauna of the ,snake ,creek formation in western ,nebraska and that of the presumably somewhat later beds of northwestern ,nevada1 which are referable to the lower ,pliocene1 may be considered together4 ,the rodents1 which are not very fully represented1 were quite modern in character and belonged mostly to extinct species of modern genera1 such as hares1 pocket-gophers1 beavers1 forerunners of the ,giant ,beaver1 marmots1 sewellels1 etc4 ,a remnant of a more ancient world1 especially characteristic of the ,miocene1 is found in the remarkable burrowers1 the horned mylagaulids which have been extinct since the lower ,pliocene4 ,carnivora were abundant1 and members of all the families which inhabit ,north ,america to-day have been obtained2 wolves1 8bear-dogs10 8hyena-dogs0 and forms like the ,dhole of ,india were common4 ,the terms 8bear-dogs0 and 8hyena-dogs0 are not to be understood as implying any relationships of these animals to bears or hyenas1 but merely a certain superficial resemblance2 these were very large members of the dog family 7,canid71 now extinct4 ,mustelines1 large and small1 are found1 and possibly some bears had already made their way from the ,old ,world1 but this is still uncertain4 ,sabre-tooth tigers and true cats1 some as large as lions and one species fairly gigantic1 were likewise characteristic of the time4 ,there was a great wealth of horses1 though the modern genus ,equus was not among them2 all the genera are now extinct and all were three-toed4 ,several distinct phyla were represented1 some progressive and advancing toward the modern forms1 others conservative and stationary4 ,browsing horses with low-crowned teeth1 grazing horses with prismatic1 cement-covered teeth1 heavier and lighter1 larger and smaller1 must have covered the plains and thronged the woods4 ,ancestral tapirs were present1 though far less common4 ,a family which seems to be utterly exotic to ,north ,america1 that of the rhinoceroses1 was present1 and of these there were three or four series1 mostly without horns1 or with a very small horn on the tip of the snout4 ,the extremely aberrant perissodactyls 7,ancylopoda71 in which the hoofs were converted into great claws1 perhaps persisted1 but the evidence is not conclusive4 ,the ,artiodactyla were1 for the most part1 totally different from those of modern times1 though several forms were ancestral to some now living4 ,peccaries more primitive than the living genus were the only representatives of the swine-like suborder2 ancestral camels and llamas were among the commonest of the hoofed animals and an extinct phylum1 that of the 8giraffe-camels0 7,alticamelus7 continued over from the ,miocene4 ,the giraffe-camels are so called1 not because of any actual relationships with the giraffes1 but on account of certain likenesses in the proportions of the animals compared4 ,alticamelus was a very large1 camel-like creature1 with remarkably elongate neck and limbs and comparatively small head1 which no doubt resembled the giraffes in browsing upon trees which were above the reach of the ordinary camels and llamas of the time4 ,it was the terminal member of a series1 or phylum1 which branched off from the main stock in ,oligocene times and pursued a course of development which was independent of the principal series1 but curiously parallel with it4 ,the deer of the lower ,pliocene were little1 graceful creatures 7,blastomeryx7 which had no antlers1 but the males were armed with sabre-like upper canine tusks1 so that they must have resembled the ,musk-,deer of ,tibet1 but were smaller and more slender4 ,the remarkable group of 8deer-antelopes10 now extinct1 was represented by ,merycodus1 a dainty little creature1 less than two feet high at the shoulder1 which had the antlers and general appearance of a small deer1 but the high-crowned grinding teeth which most antelopes have4 ,true antelopes of two different lines were also present1 though they are as yet known from little more than the bony horn-cores2 of these1 one is the flat-horned and the other the twisted-horned or strepsicerine type1 such as is illustrated by the ,eland and ,kudu of modern ,africa4 ,the latter may1 however1 be related to the peculiarly ,north ,american ,prong-,buck 7,antilocapra7 and not to the strepsicerine antelopes of the ,old ,world4 ,the last survivors of an exclusively ,north ,american family1 the oreodonts1 which were wonderfully numerous and varied from the upper ,eocene onward1 are found here4 ,the mastodons 7,gomphotherium7 of this formation had well-developed tusks in the lower as well as in the upper jaw1 and in one species the chin-region or symphysis of the lower jaw was greatly prolonged1 an ancient feature4 ,that the ,south ,american edentates had already reached the northern continent is sufficiently proved by remains of ground-sloths1 which are1 however1 too incomplete to permit identification of the genus4 ,glyptodonts have not yet been found1 but this fact does not demonstrate that they had not accompanied the ground-sloths in their migration1 for at no time did they range so far north as ,nebraska or northwestern ,nevada1 and the only mammal-bearing formation of lower ,pliocene date known in the south1 the ,alachua ,clay of ,florida1 has yielded too scanty a list of fossils to make its negative evidence at all conclusive on this point4 ,the mammals of the middle and especially of the lower ,pliocene were much stranger and more primitive than might be inferred from the foregoing brief account4 ,except several of the ,rodentia and perhaps one or two of the ,carnivora1 the genera are all extinct and such familiar terms as horses1 rhinoceroses1 camels1 etc41 can be employed only in a very comprehensive sense1 as equivalent to families4 ,the ,pliocene of ,south ,america is involved in some obscurity2 not that there is any question as to the formations1 or their order of succession1 but there is much doubt as to the limits of the epoch both above and below4 ,the latest ,pliocene fauna1 that of the ,tarija ,valley in ,bolivia1 was essentially the same as that of the ,pleistocene and contained a similarly large proportion of migrant elements from the north1 but it was evidently older and many of the species were different4 ,the two divisions of the ,araucanian fauna1 contained in the beds of ,catamarca and ,monte ,hermoso respectively1 are very much alike and need not be given separate consideration4 ,in one respect these presumably upper ,pliocene faunas formed a very strong contrast to the mammalian assemblage of the ,pleistocene1 and that is in the quite insignificant part taken by the migrants from ,north ,america4 ,of the ,carnivora there were but two representatives1 one referable to the raccoon family and one to the dogs1 while a hare and a small member of the ,artiodactyla1 of indeterminate family1 complete the list of northern forms1 though this list will doubtless be extended by future discovery4 ,the peccaries1 deer1 antelopes1 tapirs1 horses1 mastodons1 cats1 weasels1 otters1 squirrels1 mice1 etc4 had not reached the southern continent1 or were still so rare that remains of them have not been found4 ,this rarity and relative insignificance of the northern forms gave a very different aspect to the fauna4 ,on the other hand1 the indigenous ,south ,american groups were very fully represented4 ,many kinds of opossums and a few large carnivorous types1 much like the so-called ,tasmanian ,wolf 7,thylacynus71 were the remnants of a much larger assemblage of marsupials which inhabited ,south ,america in the ,miocene4 ,of the ,edentata1 there were great abundance and variety1 many large glyptodonts and some gigantic armadillos1 as well as numerous examples of normal size2 the ground-sloths1 though somewhat smaller than those of the ,pleistocene1 were mostly of gigantic size1 and true or arboreal sloths 7,tardigrada7 have been reported4 ,the very numerous rodents1 with the exception of the intrusive hare1 all belonged to typically ,south ,american families4 ,some of the rodents were gigantic and one 7,megamys71 a member of the ,chinchilla family1 was equal to a rhinoceros in size and the largest known representative of the order4 ,especially characteristic was the abundance of the cavy family 7,caviid74 ,the hoofed animals1 with the single known exception of the immigrant artiodactyl1 all belonged to the autochthonous orders1 all of which are extinct at the present time4 ,forerunners of the extraordinary genus ,macrauchenia1 which was one of the most conspicuous elements of ,pleistocene life1 were quite common in the ,pliocene and differed from the ,pampean genus chiefly in their smaller size and less advanced specialization4 ,we find here also the last survivors of another family of the ,litopterna1 the proterotheres 7,proterotheriid71 which imitated the horses in such a surprising manner that some authorities believe them to have been actually related to those perissodactyls4 ,the ,monte ,hermoso genus 7,epitherium7 had feet which were wonderfully1 though but superficially1 like those of the three-toed horses4 ,the ,toxodonta were numerous and most of them were large1 ponderous animals2 one genus 7,trigodon7 had the interesting peculiarity of a single median horn on the forehead1 much like that of a rhinoceros4 ,horned species were always rare among the indigenous groups of ,south ,american ungulates1 and all that have been discovered so far belonged to the toxodonts4 ,the remaining group1 that of the ,typotheria1 was also well represented1 both by larger and by very small forms1 some no larger than a rabbit 7,pachyrukhos74 ,the presumably lower ,pliocene 7perhaps upper ,miocene7 fauna of the ,paran formation is as yet known only from very fragmentary material4 ,representatives of the dogs1 raccoons and bears have been reported1 but the identifications are doubtful2 at all events1 these would seem to have been the most ancient of the northern immigrants4 ,a considerable number of marsupials1 both opossums and large predaceous types1 have been found4 ,the rodents were very numerous1 all belonging to ,south ,american families and some of them very large4 ,the edentates were gigantic ground-sloths and glyptodonts1 with numerous armadillos of ordinary size4 ,the hoofed animals all belonged to the indigenous ,south ,american orders1 the predominant place being taken by the toxodonts1 some of which were large4 ,there were many typotheres1 both of the larger and smaller kinds4 ,the ,litopterna were represented both by the horse-like proterotheres and the long-necked macrauchenids1 the latter smaller and less specialized than those of the ,pampean4 ,illustration3 ,,fig4 #abd4--;,head of ,horned ,toxodont 7,trigodon gaudryi74 ,pliocene of ,monte ,hermoso4 ,restored from a skull in the ,ameghino collection4 #b4 ,miocene ,north ,america4--,upper ,miocene beds cover extensive areas of the ,great ,plains region and are scattered from ,montana far into ,mexico4 ,the rich fauna is an outgrowth and development of that of the middle ,miocene1 with but few immigrant additions and1 on the other hand1 passes so gradually into that of the lower ,pliocene1 that any line of separation between them is very difficult to draw4 ,the rodents1 numerous as they are among the fossils1 are almost certainly very incompletely represented in the collections2 the families are almost all still in existence1 but nearly every genus is extinct1 and thus the vernacular names used to designate them must be understood in a broad sense4 ,hares1 mice1 pocket-gophers1 squirrels1 marmots1 beavers and the extraordinary mylagaulids were all abundant4 ,in even more strongly marked sense must the broad meaning for the vernacular names of the other mammals be emphasized1 for we have to deal almost exclusively with extinct genera1 which differed much from their modern descendants4 ,many of the ,carnivora have been obtained2 there were numerous dogs1 some rivalling the largest of existing bears in size1 true felines and sabre-tooth tigers1 which were smaller and lighter animals than the great beasts of the ,pleistocene2 weasels1 martens1 otters and raccoons1 but no bears4 ,the bears1 a family of ,old ,world origin1 are not certainly known in ,america before the ,pleistocene1 but had probably reached this continent in the ,pliocene4 ,as is so very generally true1 the commonest and best-preserved of the fossils are those of the hoofed animals4 ,the mastodons were of the four-tusked kind 7,gomphotherium or ,trilophodon71 the skull and teeth of which differed so markedly from those of the true elephants4 ,the relatively small1 low-crowned and simple grinding teeth were common to all the mastodons1 but the tusks were different from those of the larger members of the group4 ,the upper tusks were comparatively short and nearly straight and retained a band of enamel1 while the lower tusks were still shorter1 chisel-shaped and so worn as to prove that they were regularly used1 no doubt in cropping leaves2 the shortness of these lower tusks was compensated for by the great elongation of the lower jaw4 ,the head was proportionately broad and low and1 for ,proboscidea1 these were small animals1 not more than five or six feet high at the shoulder4 ,the body1 limbs and feet had already attained substantially their modern grade of structure1 advance among the ,proboscidea being chiefly restricted to the teeth and skull4 ,illustration3 ,,fig4 #abe4--,teleoceras fossiger1 a short-legged rhinoceros1 with small nasal horn2 lower ,pliocene and upper ,miocene of ,nebraska4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,four families of ,perissodactyla were represented in the upper ,miocene4 ,the rhinoceroses1 which were very abundant1 were present in considerable variety2 some were hornless1 others had a single small horn on the end of the nose4 ,among these rhinoceroses there was much difference in bodily proportions1 some being extremely heavy1 with very short legs and feet1 and these were the commonest1 while others had longer legs and less massive bodies4 ,tapirs1 on the contrary1 would seem to have been scantily represented2 at least1 they are rare among the fossils4 ,the extraordinary1 aberrant chalicotheres1 perissodactyls with claws instead of hoofs1 still persisted1 but are far better known from the lower ,miocene1 in connection with which they will be described4 ,the dominant perissodactyl family was that of the horses1 of which no less than five genera are already known4 ,there were some with very low-crowned teeth1 which must have fed principally by browsing upon leaves and such soft diet2 but the grazing kinds1 which had high-crowned1 cement-covered and very complex grinding teeth1 had come to the fore4 ,still retaining three toes in each foot1 with the middle toe so enlarged as to bear nearly the entire weight1 save in snow or soft ground1 these eminently cursorial animals1 which had the slender limbs of a deer1 must have roamed the plains in great herds4 ,still commoner were the ,artiodactyla4 ,many species of grazing camels1 which were the predominant artiodactyl family in ,north ,america during upper ,miocene times1 were the ancestors both of the true camels of the ,old ,world and the ,south ,american llamas4 ,giraffe-camels have not yet been found and no doubt they were much less abundant than in the middle ,miocene1 but that they had not completely disappeared is shown by their recurrence in the ,pliocene4 ,as compared with earlier ages1 the oreodonts had begun a rapid decline and had lost notably both in numbers and variety1 but one most curious beast 7,pronomotherium1 ,fig4 #aig1 p4 #cge7 marked the final step in the development of the short-faced1 proboscis-bearing series1 which may be traced back to its beginnings in the ,oligocene4 ,in this wonderful creature the skull was so short and deep as to suggest that of a gorilla or some other great ape4 ,no other artiodactyls even approximate these later proboscis-bearing oreodonts in the altogether exceptional form of the skull4 ,grazing oreodonts 7,merychyus71 of moderate and small size with high-crowned teeth1 were evidently quite common on the upper ,miocene plains4 ,the hornless deer and 8deer-antelopes0 differed but little from those of the lower ,pliocene4 ,peccaries were fairly abundant4 ,illustration3 ,,fig4 #abf4--,procamelus elrodi1 a large camel from the upper ,miocene4 ,restored from specimens in the ,carnegie ,museum4 ,the upper ,miocene fauna was especially characterized by the large number of mammals1 belonging to several different orders1 which had acquired the high-crowned1 persistently growing pattern of grinding teeth4 ,many of the horses1 camels1 ruminants and rodents displayed this structure1 and1 as was first pointed out by ,kowalevsky1 the explanation is probably to be found in the spread of grassy plains at the expense of the forests4 ,on account of the silica which they contain1 the grasses are very abrasive and rapidly wear the teeth down4 ,in adaptation to this new source of abundant and nutritious food1 many kinds of mammals developed a form of tooth which was fitted to compensate by growth for the loss through abrasion4 ,the middle ,miocene1 small areas of which occur in ,montana1 eastern ,oregon and northeastern ,colorado1 has received various local names1 the typical one being the ,deep ,river of ,montana4 ,very probably1 these scattered areas are not strictly contemporaneous1 but form a closely connected series4 ,that a land-connection with the eastern hemisphere existed1 is made clear by the appearance of several unmistakably ,old ,world types of animals and the beginnings of migration from ,south ,america are perhaps also to be noted1 though this cannot be positively stated4 ,the evidence for the ,south ,american connection is the finding in the middle ,miocene of ,oregon of what are believed to be the earliest remains of ground-sloths yet discovered in ,north ,america1 but the material is too scanty for altogether certain determination4 ,the smaller animals are not very well represented in the middle ,miocene faunas1 as conditions appear to have been unfavourable to their preservation2 something is known of them1 nevertheless4 ,the very curious extinct family of rodents known as the ,mylagaulid1 the presence of which was noted in the upper ,miocene and lower ,pliocene1 first appeared here4 ,these mylagaulids1 which were distantly related to the modern ,sewellel 7,aplodontia rufa71 were characterized by the great enlargement and complication of one of the grinding teeth in each jaw and the consequent reduction of the others4 ,one genus of this family1 as in the ,pliocene1 had the peculiarity1 unique among rodents1 of developing a large horn upon the nose1 like a miniature rhinoceros4 ,among the ,carnivora1 we find a great variety of dogs1 large and small1 all belonging to extinct genera1 as indeed is true of the other carnivores also4 ,true felines have been found1 but as yet1 none of the sabre-tooth series2 the abundance of the latter1 however1 in both preceding and succeeding formations1 is sufficient proof that the discovery of them in the middle ,miocene is merely a question of time4 ,mustelines were present1 and especially noteworthy is the appearance of the first ,american otters1 immigrants from the ,old ,world4 ,of the hoofed animals1 the most interesting are the ,proboscidea1 the most ancient of which that are definitely determinable in ,america occur in this horizon4 ,the place of origin and ancestry of these animals were long exasperating puzzles4 ,appearing suddenly in the ,miocene of ,europe and ,north ,america1 in which regions nothing was known that could1 with any plausibility1 be regarded as ancestral to them1 they might as well have dropped from the moon1 for all that could be told concerning their history4 ,the exploration of the ,eocene and ,oligocene beds of ,egypt has dispelled the mystery and shown that ,africa was the original home of the group1 whence they gradually spread to every continent except ,australia4 ,little is known of these earliest ,american proboscideans1 but they were doubtless small mastodons of the four-tusked type4 ,among the ,perissodactyla1 the rhinoceroses were perhaps the most conspicuous2 the native ,american stocks of this family appear to have mostly died out and to have been replaced by two or more phyla of immigrants from the ,old ,world1 some of which were hornless1 others had a small horn on the tip of the nose and others again had a second and smaller horn on the forehead4 ,tapirs1 though unquestionably present1 are rare as fossils and not well known4 ,several distinct phyla of horses may be distinguished1 which were like small ponies in size1 but of more slender form2 they were all three-toed1 but there were marked differences among them with regard to the degree to which the middle toe 7the third of the original five7 had been enlarged to carry the whole weight and the lateral toes 7second and fourth7 reduced to mere 8dew-claws40 ,while browsing horses1 with low-crowned teeth1 still persisted in large numbers1 we find also the extremely interesting beginnings of the highly complex1 cement-covered and high-crowned teeth of the grazing kinds4 ,the clawed chalicotheres were present1 though very little is known about them because of the fragmentary character of the remains4 ,the ,artiodactyla were much more varied and abundant1 though they did not rival the great assemblage of these animals found in the ,european ,miocene4 ,of the peccaries little more can be said than that they were present in these faunas4 ,the oreodonts were very numerous1 both individually and generically2 two stages of the proboscis-bearing kind are found here together1 the older1 long-faced genus 7,promerycochrus7 surviving from the ,oligocene1 while the newer ,miocene type was short-faced and had a moderate proboscis 7see ,fig4 #aif1 p4 #cgc74 ,others had more the proportions of peccaries and still others were very small and presumably aquatic in habits4 ,camels abounded1 both the grazing kinds which were ancestral to the modern forms of ,south ,america and ,asia1 and the great1 browsing giraffe-camels4 ,the hornless deer and the antlered deer-antelopes were much like those of the ,upper ,miocene1 slender and graceful little creatures1 and there were also considerably larger ruminants 7,dromomeryx7 with straight1 simple and non-deciduous horns1 which may be called antelopes4 ,illustration3 ,,fig4 #abg4--;,gigantic giraffe-camel 7,alticamelus altus7 from the middle ,miocene of ,colorado4 ,restored from specimens in the ,american ,museum of ,natural ,history4 ,the line of division between the lower ,miocene and the uppermost ,oligocene is a very obscure and difficult one to draw4 ,personally1 ,i prefer to begin the ,miocene with the widespread formation of the ,great ,plains1 which has been variously named ,arikaree1 ,harrison1 ,rosebud1 etc41 but this is a moot point4 ,concerning the lower part of these beds ,osborn says3 8,they may be either3 7#a7 ,upper ,oligocene or 7#b7 transitional from ,oligocene to ,miocene1 or 7#c7 of pure ,lower ,miocene age40 ,the upper division is referred to the ,miocene without question by any one1 but for the purposes of this rapid sketch it will be best to treat the two faunas together4 ,this many-named formation1 for which the term ,arikaree is here employed1 as having priority1 is found over extensive areas of ,south ,dakota1 northern ,nebraska and central ,wyoming4 ,the fauna was almost entirely a development from that of the ,north ,american ,oligocene1 with very little admixture of foreign elements1 so that the land communication with the eastern hemisphere must have been difficult4 ,in this1 as in most of the ,miocene formations1 the smaller mammals are not fairly represented1 and it is evident that much remains to be learned with regard to them2 this is especially true of the upper division of this stage4 ,illustration3 ,,fig4 #abh4--,most ancient ,american ,antelope 7,dromomeryx antilopina71 middle ,miocene4 ,restored from specimens in the ,carnegie ,museum and ,princeton ,university4 ,the rodents1 which were fairly numerous1 were directly continuous with those of the upper ,oligocene and included forms which were more or less distantly connected with the modern hares1 squirrels1 beavers1 sewellels1 pocket-gophers and kangaroo-rats4 ,a few ,insectivora of doubtful reference have been found4 ,among the ,carnivora there was also considerable variety3 dogs1 large and small1 were abundant1 but all of them were decidedly primitive from the modern standpoint2 the cats were represented both by the true felines1 which were probably immigrants1 and by the sabre-tooth series4 ,there were several large and powerful mustelines1 or members of the weasel family1 which were likewise immigrants1 one of which resembles in many ways the modern ,wolverene 7,gulo74 ,very interesting is the beginning of the raccoon family 7,procyonid7 or1 at least1 what is believed to be such1 which arose from a branch of the dogs2 this most ancient of the raccoons was ,phlaocyon1 a small and slender animal4 ,the earliest traces of the ,proboscidea in ,america have been reported from this formation1 but the fragmentary specimens are inconclusive4 ,the ,perissodactyla are among the commonest fossils4 ,the rhinoceroses belonged to native stocks1 including both the horned and hornless forms4 ,the horned genus 7,diceratherium7 differed from all other rhinoceroses in having a transverse pair of horns on the nose1 and the species of the lower ,miocene were quite small and light2 the hornless genus 7,cnopus7 was a larger and heavier animal4 ,tapirs are rare as fossils and consequently not well known4 ,while there were several kinds of horses1 they all agreed in having short-crowned and relatively simple grinding teeth and three-toed feet2 they were smaller and of lighter1 more slender build than those of the middle ,miocene4 ,the wonderful aberrant perissodactyls with clawed feet1 the chalicotheres 7suborder ,ancylopoda71 appear to have been more abundant in the ,arikaree than at any other time in ,north ,america1 though their history in this continent extends from the middle ,eocene to the lower ,pliocene4 ,moropus1 the lower ,miocene genus1 was as grotesque a creature as could well be imagined and1 in advance of experience1 no one ever did imagine such a beast4 ,with rather small and somewhat horse-like head1 long neck1 long fore limbs and shorter hind limbs1 these extraordinary animals united short1 three-toed feet1 which were armed with enormous claws4 ,the long persistence 7to the ,pleistocene of ,asia7 and wide geographical range of the chalicotheres are sufficient evidence that their very unusual structure must have been advantageous to them1 but the problem of their habits and mode of life is still unsolved4 ,from the character of the teeth1 the long neck and fore limbs1 it may1 however1 be inferred that they fed chiefly upon the leaves of trees4 ,illustration3 ,,fig4 #abi4--,the small1 paired-horned rhinoceros 7,diceratherium cooki7 of the lower ,miocene4 ,restored from a skeleton in the ,carnegie ,museum1 ,pittsburgh4 ,illustration3 ,,fig4 #acj4--;,a chalicothere 7,moropus elatus7 of the lower ,miocene4 ,restored from a skeleton in the ,carnegie ,museum1 ,pittsburgh4 ,even more numerous and varied were the ,artiodactyla4 ,peccaries of a primitive sort were common1 and we find the last of the series of 8giant pigs10 which had been a very conspicuous group throughout the ,oligocene4 ,the lower ,miocene genus1 ,dinohyus1 was a monstrous beast1 six feet or more in height1 with formidable canine tusks and a very long head made grotesque by bony excrescences upon the skull and jaws4 ,for a pig1 the legs were very long and the feet slender1 having but two toes4 ,the oreodonts were present in great numbers1 both small and large forms2 except for bodily stature and modifications of the head1 they all looked very much alike2 ,merycochrus1 with its incipient proboscis1 here made its first appearance4 ,the last representatives of a family 7,hypertragulid7 of small and graceful artiodactyls are found in this formation4 ,one of these 7,syndyoceras1 see ,fig4 #bae1 p4 #djc71 an animal considerably larger than the existing ,musk-,deer1 was in its way even more bizarre-looking than the chalicotheres2 with an antelope-like head1 it had four horns1 one pair over the eyes1 curving inward1 and a shorter pair1 with outward curvature1 on the muzzle4 ,another genus 7,hypertragulus7 was very much smaller and very slender4 ,the camels were beginning to diversify and give rise to several phyla4 ,one of the genera 7,protomeryx71 which did not much exceed a sheep in size1 probably represented the main stock1 which led to the camels and llamas of to-day4 ,a second 7,stenomylus7 was a still smaller animal1 with remarkably long and slender legs1 and might be called a 8gazelle-camel10 while a third 7,oxydactylus1 see ,fig4 #bji1 p4 #cib71 which was larger and apparently the beginning of the giraffe-camels1 was noteworthy for its long neck4 ,all of these lower ,miocene camels had deer-like hoofs1 the characteristic pad or cushion which gives such an exceptional appearance to the feet of modern llamas and camels not being fully developed till a later period4 ,a very important new element in the ,north ,american fauna was the appearance of the first deer 7,blastomeryx71 which came in the latter part of the ,arikaree stage and were the forerunners of a renewed immigration from the ,old ,world1 which had been broken off during the upper ,oligocene4 ,this1 however1 is a disputed point2 ,professor ,osborn and ,dr4 ,matthew believe that these animals were truly indigenous and derived from a long line of ,american ancestry4 ,the same genus continued through the middle ,miocene1 as we have already seen1 and therefore no further description of it is called for4 ,the limits of the ,south ,american ,miocene are very doubtful4 ,the ,paran formation1 here regarded as lower ,pliocene1 may prove to be more properly referable to the upper ,miocene4 ,no other upper ,miocene is known4 ,illustration3 ,,fig4 #aca4--,the gazelle-camel 7,stenomylus hitchcocki7 of the lower ,miocene4 ,restored from skeletons in the ,carnegie ,museum1 ,pittsburgh4 ,to the earlier1 probably middle1 ,miocene may be referred the wonderful ,santa ,cruz fauna of ,patagonia4 ,it is extremely difficult to convey to the reader any adequate conception of this great assemblage of mammals1 because most of them belonged to orders which have altogether vanished from the earth and are only remotely like the forms with which we are familiar in the northern hemisphere4 ,to one who knows only these northern animals1 it seems like entering another world when he begins the study of the ,santa ,cruz fossils4 ,if any ,north ,american mammals had then entered ,south ,america1 which is not probable1 they had not extended their range as far as ,patagonia4 ,marvellously rich and varied as the ,santa ,cruz fauna was1 it did not contain everything that we should expect to find in it2 several recent families of undoubtedly indigenous ,south ,american origin have left no ancestors in the early ,miocene formations4 ,for this1 there are several obvious reasons4 ,in part1 these gaps in the history are merely due to the accidents of collecting and some of them will almost certainly be filled by future exploration4 ,other absentees will probably never be found1 because the ,santa ,cruz beds are known only in the very far south1 and the ,miocene climate of the region1 though much milder and more genial than the present one1 must have been unsuitable for many tropical animals4 ,again1 the ,patagonia of that time appears to have been a country of open plains1 with few trees1 and hence arboreal forms were rare4 ,illustration3 ,,fig4 #acb4--;,diagram to illustrate the comparative sizes of the ,santa ,cruz mammals1 a modern pointer dog1 within the rectangle1 to give the scale4 #a4 ,cladosictis lustratus1 predaceous marsupial4 #b4 ,protypotherium australe1 typothere4 #c4 ,eocardia excavata1 rodent4 #d4 ,stegotherium tesselatum1 armadillo4 #e4 ,propalohoplophorus australis1 glyptodont4 #f4 ,hapalops longiceps1 ground-sloth4 #g4 ,thoatherium minusculum1 litoptern4 #h4 ,astrapotherium magnum1 astrapothere4 #i4 ,prothylacynus patagonicus1 predaceous marsupial4 #aj4 ,theosodon garrettorum1 litoptern4 #aa4 ,nesodon imbricatus1 toxodont4 ,while great numbers of large1 flightless birds1 some of them of enormous size1 were entombed in the volcanic ash and dust which were spread over such wide areas and to such great depths1 the extreme scarcity of reptiles is surprising2 a few remains of lizards have been found1 but no snakes1 crocodiles1 or tortoises1 and we have no information as to the plant-life of the region at that time4 ,the mammals were almost all of small or moderate size2 only one or two species were really large4 ,one very striking and characteristic feature of the ,santa ,cruz fauna is the great abundance of marsupials which it contained and which resembled more or less those of modern ,australia4 ,there were no true ,carnivora and their places were taken by a variety of carnivorous marsupials1 some of which 7e4g4 ,prothylacynus7 were as large as wolves and were closely similar to the so-called ,tasmanian ,wolf 7,thylacynus74 ,another genus 7,borhyna7 had a short1 bullet head1 not unlike a small ,puma in appearance and1 besides1 there were many smaller beasts of prey1 in size like badgers and minks4 ,opossums were common and there were many very small herbivorous marsupials1 which resembled1 though perhaps but superficially1 the ,australian phalangers4 ,at the present day ,south ,america contains no ,insectivora1 but in the ,santa ,cruz there was one family 7,necrolestid7 of this order which bore considerable resemblance to the 8golden moles0 of ,south ,africa4 ,an extraordinary variety of rodents inhabited ,patagonia in ,santa ,cruz times1 all of them belonging to the ,hystricomorpha1 or porcupine suborder1 and all referable to existing ,south ,american families4 ,there were none of the northern forms of rodents1 neither rats1 mice1 squirrels1 marmots1 hares1 nor rabbits1 but a very numerous assembly of tree-porcupines1 cavies1 chinchillas1 coypus and the like4 ,the genera1 though closely allied to existing ones1 are all extinct1 and the animals were very generally smaller than their modern descendants4 ,a few small monkeys of unmistakably ,neotropical type have been found1 but like other arboreal and forest-living animals1 they are very rare among the fossils4 ,the ,edentata were more abundant and diversified than at any other time in ,south ,american history of which the record is preserved4 ,two of the modern subdivisions of this order have not been certainly identified in the ,santa ,cruz collections1 the arboreal sloths and the anteaters1 and though they may be found there at any time1 it will only be as stragglers from the warmer forested regions to the north1 where these forms had doubtless long been present4 ,unfortunately1 however1 nothing is directly known concerning the life of those regions in ,miocene times4 ,on the other hand1 three groups of edentates1 two of them now extinct1 were very copiously represented in the ,santa ,cruz formation1 the armadillos1 glyptodonts and ground-sloths4 ,of the many armadillos1 some quite large1 others very small1 only a few can be regarded as directly ancestral to those now in existence2 the truly ancestral forms were probably then living in the forests of ,brazil and northern ,argentina1 in the same areas as the ancestral tree-sloths and anteaters4 ,in comparison with the giants of the ,pliocene and ,pleistocene1 the ,santa ,cruz glyptodonts were all small1 the carapace rarely exceeding two feet in length1 and1 what it is particularly interesting to note1 they departed much less widely from the armadillo type than did their gigantic successors4 ,the ground-sloths were present in actually bewildering variety and they also were very small as compared with the huge animals of the ,pleistocene1 none of them exceeding the ,black ,bear in height or length1 though proportionally much more massive1 and many were no bigger than foxes4 ,they had small heads1 long bodies1 heavy tails and short1 thick legs2 their teeth show that they were plant-feeders1 but their feet were armed with long1 sharp and formidable claws4 ,among this great host of ,santa ,cruz ground-sloths may readily be noted the probable ancestors of the gigantic creatures which were such characteristic elements of the ,pliocene and ,pleistocene faunas4 ,there was an extraordinarily rich and varied assemblage of hoofed animals1 all utterly different from those of the northern hemisphere and belonging to groups which have never been found outside of ,south and ,central ,america4 ,of these groups there were five1 which by different writers are variously regarded as orders or suborders1 a matter of very secondary importance4 ,individually1 the commonest of the hoofed mammals were the ,toxodonta1 which ranged in size from a sheep to a tapir1 heavily built and clumsy creatures1 with absurdly small1 three-toed feet2 in some of the species there was a small median horn on the forehead4 ,as with the glyptodonts and ground-sloths1 the contrast in size between the ,santa ,cruz ancestors and the ,pleistocene descendants was very striking4 ,a very numerous and varied group was that of the ,typotheria1 all small animals1 some no larger than rabbits1 others the size of small foxes4 ,it requires a decided effort to think of these typotheres as being really hoofed animals at all1 as their whole appearance must have been much more like that of rodents1 yet their structure clearly demonstrates their near relationship to the toxodonts4 ,still a third group of the same series1 the ,entelonychia1 is of great interest1 for1 as in the chalicotheres of the northern hemisphere1 the hoofs had been transformed into claws and their five-toed feet had a truly grotesque appearance1 not diminished by the long and powerful limbs and relatively small head4 ,this is the third example of that paradoxical creature1 a 8hoofed animal0 with claws instead of hoofs1 and in each of the three instances1 there is every reason to believe1 the transformation proceeded independently4 ,among the perissodactyls the chalicotheres 7p4 #bch7 underwent this change2 in ,north ,america the ,agriochrid1 a family of artiodactyls1 had a very similar history1 while in ,south ,america the ,entelonychia arose from the same stock as the toxodonts1 with which they were nearly allied4 ,they were among the largest animals of ,santa ,cruz times and ranged in size from an ox to a rhinoceros4 ,there was a fourth group1 the ,astrapotheria1 concerning which our knowledge is tantalizingly incomplete1 some species of which were the largest of known ,santa ,cruz mammals1 while others were much smaller4 ,they had short1 domed heads1 with a considerable proboscis1 and were armed with formidable tusks1 which were the enlarged canine teeth1 the only known instance of large canine tusks among the indigenous ,south ,american hoofed animals4 ,the limbs were long and not very massive1 the feet short1 five-toed and somewhat elephantine in appearance4 ,these bizarre animals would seem to have held a rather isolated position among the ,south ,american ungulates1 and though they may be traced back to the most ancient mammal-bearing beds of that continent1 their relationships are still obscure2 much more complete material must be obtained before this problem can be definitely solved4 ,both the ,astrapotheria and the ,entelonychia died out shortly after the end of the ,santa ,cruz4 ,from many points of view the most interesting members of the ,santa ,cruz fauna were the ,litopterna1 an order which also went back to the earliest ,south ,american ,tertiary4 ,in the ,miocene and ,pliocene the order was represented by two very distinct families1 the ,macrauchenid and ,proterotheriid1 which were superficially very unlike4 ,in the ,santa ,cruz beds is found a genus 7,theosodon7 which was apparently the direct ancestor of the ,pampean ,macrauchenia4 ,the ,miocene genus was a much smaller animal and had hardly more than an incipient proboscis1 but otherwise was very like its ,pampean successor2 it was somewhat larger and heavier than a ,llama and probably bore some resemblance to that animal in appearance4 ,the long1 narrow head1 with its prehensile upper lip1 must have had an almost reptilian likeness from the numerous uniform and sharp-pointed teeth with which the front of the jaws was supplied2 the neck was elongate1 the body short and rather slender and the legs long1 ending in three nearly equal toes4 ,the proterotheres1 on the other hand1 were almost the only ,santa ,cruz ungulates which had nothing outr or grotesque about them to the eye of one habituated to the faunas of the northern hemisphere4 ,they were small1 graceful animals1 very like the ,miocene horses of the north in their proportions1 though having much shorter necks and shorter1 heavier heads4 ,in some genera of this family 7e4g4 ,diadiaphorus1 ,proterotherium7 the feet were three-toed and most surprisingly horse-like in shape1 but one genus 7,thoatherium7 was absolutely single-toed1 more completely monodactyl than any horse4 ,the horse-likenesses ran all through the skeleton and are so numerous and so striking that several writers have not hesitated to incorporate the ,litopterna with the ,perissodactyla1 but this ,i believe to be an error4 ,if the proterotheres were not perissodactyls1 as ,i am convinced they were not1 they afford one of the most remarkable examples of convergent evolution among mammals yet made known4 #c4 ,oligocene ,north ,america4--,the ,john ,day formation of eastern ,oregon represents the upper ,oligocene and has yielded a very extensive series of mammals1 though with some obvious gaps that remain to be filled by future work4 ,the land-connection with the ,old ,world which had existed in the lower ,oligocene and was restored in the lower1 or at latest in the middle1 ,miocene1 was interrupted in ,john ,day times1 and so the mammals assumed a purely indigenous character4 ,no opossums or other marsupials have been found1 and nothing is known of the ,insectivora4 ,of the ,carnivora1 there were but three families1 and one of these1 the mustelines1 was represented but scantily by a few small species4 ,cats of the sabre-tooth subfamily were common and one species was quite large1 almost equalling the ,jaguar in length2 but most of the species were small1 much smaller than the ,pleistocene members of the group4 ,true cats are not definitely known to have been present1 but there were two genera 7,nimravus and ,archlurus7 which have been called the 8false sabre-tooths10 which may prove to be referable to that series4 ,the dogs1 on the other hand1 were remarkably numerous and diversified1 more so than ever before or since2 none of them was very large1 the largest but little exceeding the ,timber ,wolf in size1 and some were extremely small2 but the number of distinct genera and species and the differences among them are quite remarkable4 ,both long and short-faced forms and early stages of the 8bear-dogs10 and 8hyena-dogs10 and ancestral forms of the wolves and dholes may be distinguished1 a truly wonderful assemblage4 ,the rodents also were numerous and varied1 including ancient and extinct genera of the beavers1 squirrels1 mice1 pocket-gophers and hares and the earliest distinguishable ancestors of the sewellels 7,aplodontiid74 ,the remainder of the known ,john ,day fauna was composed of artiodactyls and perissodactyls4 ,the latter had suffered serious losses as compared with the preceding or ,white ,river stage4 ,up to and through ,white ,river times the perissodactyls had held their own in actual diversity1 though the rise of the artiodactyls had put an end to the dominant position which they had maintained in the ,eocene4 ,with the ,john ,day the actual decline may be said to have begun4 ,the rhinoceroses were represented chiefly by the diceratheres1 with a transverse pair of horns1 some species of which were much larger than those of the lower ,miocene4 ,hornless rhinoceroses have not yet been certainly found1 though there is every reason to believe that they then existed1 as they unquestionably did both before and after4 ,tapirs occurred but rarely and the horses were individually abundant1 though in no great diversity2 they were smaller and lighter than the horses of the lower ,miocene4 ,enough has been found to demonstrate the presence of the clawed chalicotheres1 but not to show how they differed from their immediate successors4 ,in the number of individuals1 species1 genera and families1 the artiodactyls of the ,john ,day much exceeded the perissodactyls4 ,the peccaries were numerous1 but smaller and more primitive than those of the succeeding age1 as were also the giant pigs1 or entelodonts1 but the latter were very large4 ,the peculiarly ,north ,american family of the oreodonts was very numerously represented1 and one genus 7,promerycochrus71 comprising animals not unlike the ,wild ,boar in size and shape1 was the probable beginning of the series of proboscis-bearing oreodonts1 which led to such grotesque forms in the middle and upper ,miocene4 ,a family closely allied to the oreodonts1 and by many writers included in the latter1 is the very remarkable group of the ,agriochrid1 which was distinguished by the long1 stout and cat-like tail and by the possession of claws instead of hoofs4 ,the family is not known to have existed later than the ,john ,day and no trace of it has been found in the succeeding formations4 ,the camels seem to be all comprised in a single genus 7,protomeryx7 which was the same as that found in the lower ,miocene4 ,a very small and dainty little creature 7,hypertragulus7 belonged to another family1 the relationships of which are not clear4 ,to the middle and lower ,oligocene is referred the great ,white ,river formation of ,south ,dakota1 ,nebraska1 ,wyoming1 etc41 which is divisible into three clearly marked substages4 ,the ,white ,river contains the best-known fauna of all of the ,north ,american ,tertiaries1 for collecting in these beds has been carried on for more than sixty years1 and a greater number of complete and nearly complete skeletons has been secured than from any of the other formations4 ,it is plainly evident that a land-connection existed with the ,old ,world1 which was interrupted in the ,john ,day1 as is shown by the intermigration of characteristic forms2 but some barrier1 presumably climatic1 prevented any complete interchange of mammals1 and very many genera and even families remained confined to one continent or the other4 ,the aspect of the ,white ,river fauna changes in accordance with the direction from which it is approached4 ,if one comes to the study of it from the ,eocene1 it displays a very modern aspect1 given by the almost complete disappearance of the archaic groups of mammals and by the great multiplication of genera and species belonging to the progressive orders4 ,these genera1 it is true1 are all extinct1 but many of them stood in an ancestral relationship to modern forms4 ,on the other hand1 if approached from the ,miocene side1 the ,white ,river mammals seem to be very ancient and primitive and very different from anything that now lives4 ,we speak of horses and rhinoceroses1 dogs and cats1 in this fauna1 but those terms can be employed only in a very wide and elastic sense to designate animals more or less distantly allied to those of the present day4 ,illustration3 ,,fig4 #acc4--a4 ,archotherium4 #b4 ,ancestral camel 7,pobrotherium74 #c4 ,merycoidodon4 #d4 ,agriochrus4 #e4 ,ancestral horse 7,mesohippus74 #f4 ,hoplophoneus4 #g4 ,bothriodon4 #h4 ,hynodon4 #i4 ,cursorial rhinoceros 7,hyracodon74 #aj4 ,protoceras4 #aa4 ,hornless rhinoceros 7,cnopus74 ,several species of opossums1 some of them very small1 were the only marsupials in ,north ,america then1 as they are now4 ,there was quite a variety of ,insectivora2 some were survivals of a family that was abundant in the ,eocene1 others1 like the hedgehogs1 moles and shrews1 were probably immigrants4 ,here we find the last of a group 7order or suborder7 of ancient and primitive flesh-eaters1 the ,creodonta1 that had played a great rle in the ,eocene and ,paleocene of ,north ,america and ,europe4 ,in ,white ,river times but a single family 7,hynodontid71 with two genera1 remained of the ,eocene host4 ,one of these genera 7,hemipsalodon71 a very large beast of prey1 which was almost identical with the ,old ,world genus ,pterodon1 was confined to the lower substage of the ,white ,river beds in the ,northwest ,territory of ,canada2 the other1 ,hynodon1 which was also an ,old ,world form1 was represented abundantly in the ,united ,states by many species4 ,in size1 these species ranged from a small fox to a large wolf1 but they all had disproportionately large heads1 and small1 weak feet1 with blunt claws1 so that they must have been very curious-looking creatures and were probably carrion-feeders rather than active catchers of prey4 ,the ,white ,river members of the family were migrants from the eastern hemisphere1 for1 though small and primitive representatives of it occurred in the ,north ,american ,eocene1 as well as in the corresponding formations of ,europe1 the family appears to have died out in ,america and to have been renewed by the ,oligocene migration4 ,illustration3 ,,fig4 #acd4--,white ,river titanothere 7,titanotherium robustum7 reduced to the same scale as ,fig4 #acc4 ,coincident with this decline of the creodonts and1 no doubt1 causally connected with it1 was the rise of the true ,carnivora1 which for the first time were numerous and were divisible into three distinct families4 ,small and primitive representatives of the wolves 7,daphnus7 and possibly also of the foxes 7,cynodictis7 were quite common1 and there were a few species of the musteline family1 evidently immigrants and the most ancient yet found in ,america4 ,there were several species of the sabre-tooth cats 7,dinictis and ,hoplophoneus7 all of which1 except in the uppermost substage1 were quite small1 few of them exceeding the ,canada ,lynx in size4 ,a much larger animal 7,eusmilus1 also ,european7 appeared in the latter part of the stage4 ,none of the true cats1 or feline subfamily1 has been obtained4 ,nothing is yet known of the time and place of origin of the sabre-tooth series1 for they appeared at approximately the same date in ,europe and ,america1 and in neither continent have any possible ancestors been found in preceding formations4 ,the problem is like that of the ,proboscidea 7see p4 #bcd71 but ,egypt has given no help in the case of the sabre-tooths1 and1 by a process of elimination1 we reach the conclusion that these strange creatures probably arose somewhere in ,asia and sent out migrants eastward and westward4 ,the ,rodentia were fairly abundant and present a strange mixture of ancient and comparatively modern types4 ,one very common genus 7,ischyromys71 which was the last remnant of a family almost limited to the ,north ,american ,eocene1 was associated with the earliest ,american mice1 arboreal and ground squirrels1 beavers and rabbits2 some1 if not all1 of these were immigrants4 ,the hoofed mammals were present in fairly bewildering variety1 but were restricted to the two orders of the ,perissodactyla and ,artiodactyla4 ,the ,perissodactyla1 while they no longer had the relatively dominant position which they held in the middle ,eocene 7see p4 #bgj71 had suffered no actual loss2 and no less than seven families of them1 or six by another scheme of classification1 had members in the ,north ,america of ,white ,river times1 a very notable difference from the present order of things1 when there are but three families in the entire world1 none of which enters ,north ,america4 ,the ,eocene family of the titanotheres became extinct at the end of the lower substage of the ,white ,river1 but in that substage there was a marvellous abundance of these huge beasts1 some of which were of almost elephantine stature and bulk4 ,the pair of great bony1 horn-like protuberances on the nose varied much in size and form in the different species1 short to very long1 triangular1 cylindrical1 flattened and shovel-shaped1 and gave these ungainly creatures somewhat the appearance of strange and very large rhinoceroses4 ,the titanotheres were a typically ,north ,american family1 but sent migrants to the ,old ,world1 at least two species reaching southeastern ,europe4 ,rhinoceroses too were extremely numerous and diversified throughout the stage and are very plainly divisible into three strongly contrasted series1 which are sometimes regarded as three subdivisions of the same family and sometimes put into two separate families4 ,one of these series1 the hyracodonts 7,hyracodon71 was composed of small1 long-necked and long-legged1 slender and lightly built1 cursorial animals1 but with short1 heavy heads1 which gave them a somewhat clumsy look2 having neither horns nor tusks1 they were entirely defenceless and depended for their safety upon speed alone4 ,the second series1 or amynodonts 7,metamynodon71 formed the very antithesis of the first1--large1 heavy1 short-necked1 and short-legged and probably amphibious in manner of life1 they were armed with formidable tusks2 and their skulls were so curiously modified as to bear a distinct resemblance to the skull of a huge carnivore4 ,the amynodonts migrated to the ,old ,world and occur in the ,oligocene of ,france1 but the hyracodonts would seem never to have left ,north ,america4 ,the third series1 that of the true rhinoceroses1 comprised several genera at different levels in the ,white ,river beds 7,trigonias1 ,cnopus1 etc472 they were of uncertain origin and it has not yet been determined whether they were immigrants or of native stock4 ,many species have been found1 varying much in size1 up to that of a modern tapir1 and not unlike one in proportions1 for they were of lighter build and had relatively longer legs than any existing rhinoceros4 ,the species of the lower and middle substages were all hornless1 but in the uppermost substage we find skulls with a pair of nasal horns in an incipient stage of development4 ,this was the beginning of the paired-horned rhinoceroses 7,diceratherium7 which so flourished in the ,john ,day and the lower ,miocene4 ,illustration3 ,,fig4 #ace4--;,hornless rhinoceros 7,cnopus tridactylus7 of the ,white ,river stage4 ,restored from a skeleton in the ,american ,museum4 ,of the horses there was no great variety and all the species so far discovered are included in a single genus 7,mesohippus71 though there was a decided increment in the size of the successive species from the earlier to the later portion of the stage4 ,looked at superficially1 it seems absurd to call these little creatures 8horses0 at all and the term can be justified only as implying that they were ancestral members of the family4 ,the largest of the ,white ,river species hardly exceeded a sheep in size and all of them had comparatively short necks1 long and slender legs and three-toed feet4 ,the low-crowned grinding teeth show that they were browsers1 not grazers4 ,the abundant ,eocene family of the ,lophiodontid made its last appearance in the ,white ,river1 where it was scantily represented by slender1 long-legged animals 7,colodon71 with feet singularly like those of the contemporary horses1 except that there were four toes in the front foot4 ,tapirs 7,protapirus7 were very much less common than rhinoceroses or horses and were hardly half as large as the existing species of the family and of relatively far more slender form2 the development of the proboscis had already begun4 ,lastly1 the presence of the clawed chalicotheres has been reported from the lower ,oligocene of ,canada1 but the material is too fragmentary for generic reference4 ,though the number of artiodactyl families yet identified among the ,white ,river fossils is no larger than that of the perissodactyl families1 the artiodactyls greatly preponderated in individual abundance4 ,the peccaries1 which were fairly common1 resembled those of the ,john ,day1 but were considerably smaller4 ,of the camels1 there were two series1 one of which 7,eotylopus71 lately described by ,dr4 ,matthew1 is of yet unknown significance1 while the other 7,pobrotherium7 was apparently the ancestor common to all the subsequent phyla of camels and llamas4 ,this extremely interesting genus had species which ranged in size from a gazelle to a sheep1 had two toes in each foot1 a moderately elongate neck and teeth which were beginning to assume the high-crowned character4 ,from this it may be inferred that those animals were1 partly at least1 of grazing habit1 which was rare among ,white ,river ungulates1 most of which fed upon leaves and soft and succulent plants4 ,an extinct family1 the ,hypertragulid1 were a greatly diversified group of dainty little creatures1 one of which 7,hypisodus7 was no larger than a rabbit and had high-crowned teeth4 ,the other genera 7,leptomeryx1 ,hypertragulus7 must have resembled in form and proportions the tiny little chevrotains or 8mouse-deer0 of the ,east ,indian islands4 ,late in the age arose a larger form of this family1 nearly equalling the ,musk-,deer in size1 the extraordinary genus ,protoceras1 which was1 especially the males1 a grotesque object4 ,the males had a pair of upper canine tusks and two pairs of prominent long protuberances on the skull4 ,this1 or some similar form1 must have been the ancestor of the still more bizarre ,syndyoceras of the lower ,miocene4 ,the oreodonts were by far the commonest of ,white ,river mammals1 and evidently they roamed the woods and plains in great herds4 ,there were several species1 larger and smaller1 of the abundant genus 7,merycoidodon7 but the largest did not surpass a modern peccary in size and was somewhat like that animal in appearance1 but had a shorter head and much longer tail4 ,in the upper substage appeared a very peculiar genus of this family 7,leptauchenia71 animals with short1 deep1 almost monkey-like heads1 and presumably aquatic in habits4 ,the agriochrids were very much less common2 they may be described roughly as oreodonts with very long1 cat-like tails and clawed feet4 ,illustration3 ,,fig4 #acf4--,merycoidodon culbertsoni1 the most abundant of ,white ,river oreodonts4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,all of the foregoing artiodactyl families were exclusively ,north ,american in ,oligocene distribution2 even the camels did not reach ,asia till the ,pliocene1 and the other families never invaded the ,old ,world at all4 ,there were1 however1 two additional families1 which also occurred in the eastern hemisphere1 whence one of them1 and possibly the other1 was derived4 ,the unquestionably ,old ,world family1 that of the anthracotheres1 was represented in the ,white ,river by two genera 7,bothriodon and ,anthracotherium71 which were short-legged1 long-snouted1 swine-like animals1 which have no near relations in the modern world4 ,the other family1 the giant pigs1 which we have already met with in the lower ,miocene and upper ,oligocene1 is of doubtful origin1 and nothing has yet been found in the preceding formations of either ,north ,america or ,europe which can be regarded as ancestral to them4 ,the ,white ,river genus 7,archotherium7 was very like the ,john ,day and ,arikaree genera1 but most of the species were much smaller and some were not so large as a domestic pig4 ,in the uppermost beds1 however1 are found huge species1 which rivalled those of the subsequent formations4 ,that these strange animals were rooters and diggers and therefore pig-like in habits is indicated by the manner in which the teeth are worn4 ,illustration3 ,,fig4 #acg4--;,giant pig 7,archotherium ingens7 from the lower ,white ,river stage4 ,restored from a skeleton in the museum of ,princeton ,university4 ,south ,america4--,the older continental ,tertiary formations of ,south ,america cannot be correlated with those of ,north ,america or ,europe1 because they have nothing in common4 ,difficult as it is to give a correct and adequate conception of the ,tertiary mammalian life of the northern hemisphere to one who has not made a study of it1 it is far more difficult in the case of ,south ,america4 ,the stock of adjectives1 such as 8peculiar10 8bizarre10 8grotesque0 and the like1 already overworked in dealing with northern forms1 is quite hopelessly inadequate where everything is strange4 ,in addition to this1 we are seriously handicapped in treating of the ,oligocene and ,eocene of ,south ,america by very incomplete knowledge4 ,many fossils have been collected and named1 but the great majority of these are known only from teeth2 a few skulls and limb-bones have been described1 but no skeletons1 and therefore much is very uncertain regarding these faunas4 ,the ,deseado formation 7,pyrotherium ,beds7 has been variously referred by different writers from the upper ,cretaceous to the lower ,miocene1 but its most probable correlation is with the ,oligocene4 ,though most of the mammalian groups are the same as those of the ,santa ,cruz1 the proportions of the various orders in the two faunas are very different1 but1 to some extent1 the difference is probably illusory and due to the conditions of fossilization1 for1 as a rule1 the small mammals are much less frequent and well preserved in the older beds4 ,as in the ,santa ,cruz1 the marsupials were the only predaceous mammals1 and some of them attained gigantic size2 but no such variety of these beasts of prey has been found in these beds as occurred in the middle ,miocene4 ,in addition1 there were numerous small herbivorous marsupials4 ,one of the most striking differences from the ,santa ,cruz fauna was in the very much smaller number of ,edentata1 which1 instead of being extremely common1 are quite rare among the fossils4 ,no doubt there was a real and substantial difference in this respect1 but it was probably not so great as it seems1 and the same three suborders are found in both formations4 ,one of the few ground-sloths that have been obtained was very large 7,octodontherium crassidens71 a much larger animal than any species of the suborder that is known from the ,santa ,cruz4 ,the glyptodonts were also rare1 and only two genera and species have been described from very scanty remains4 ,armadillos1 on the other hand1 were much more common1 and no less than eleven genera have been named1 three of which occurred also in the ,santa ,cruz4 ,among these was the remarkable genus ,peltephilus1 in which the anterior two pairs of plates of the head shield were modified into horn-like spines4 ,equally striking was the remarkable diminution of the ,rodentia1 as compared with those of the ,santa ,cruz1 though1 of course1 this is an inaccurate mode of stating the truth1 occasioned by the fact that we are following the history in reverse order4 ,it would be preferable to say that the rodents underwent a remarkable expansion in the ,santa ,cruz4 ,these rodents of the ,deseado stage are the most ancient yet discovered in ,south ,america and represent only two families1 both belonging to the ,hystricomorpha1 or porcupine group4 ,if1 as ,dr4 ,schlosser and other ,european palontologists maintain1 the ,hystricomorpha were all derived from a family of the ,european ,eocene1 this would necessitate a land-connection between ,south ,america and the ,old ,world independent of ,north ,america1 for the latter continent had no hystricomorph rodents until the connection between the two ,americas was established4 ,the great bulk of the ,deseado fauna is made up1 so far as individual abundance is concerned1 of hoofed animals belonging to the typically ,south ,american groups4 ,the ,toxodonta were represented partly by genera which were the direct ancestors of the common ,santa ,cruz genera 7,pronesodon1 ,proadinotherium71 and1 more numerously1 by a very peculiar family1 the ,notohippid1 which had highly complex1 cement-covered grinding teeth4 ,still a third family of this suborder1 the ,leontiniid1 was highly characteristic of the ,deseado fauna and is not known from the ,santa ,cruz4 ,these were large animals1 with a small horn on the tip of the nose and low-crowned1 comparatively simple grinding teeth4 ,even more abundant were the ,typotheria1 small forms which were ancestral to the ,santa ,cruz genera1 larger ones which died out without leaving successors and one quite large animal 7,eutrachytherus7 which seems to have been the ancestor of the ,pliocene and ,pleistocene ,typotherium4 ,this series is not known to have been represented in the ,santa ,cruz and may have withdrawn from ,patagonia at the end of the ,deseado stage4 ,illustration3 ,,fig4 #ach4--;,horned toxodont 7,leontinia gaudryi71 ,deseado stage4 ,restored from a skull in the ,ameghino collection4 ,the ,entelonychia1 those strange toxodont-like animals with claws instead of hoofs1 were much more numerous and varied than they were afterward in the ,santa ,cruz1 when they were on the verge of extinction1 and included both very small and very large species4 ,the ,pyrotheria1 a suborder which is not met with in the ,santa ,cruz or later formations1 likewise included some very large forms4 ,the typical genus1 ,pyrotherium1 included large1 relatively short-legged and very massive animals2 the upper incisors formed two pairs of short1 downwardly directed tusks1 and in the lower jaw was a single pair of horizontally directed tusks2 the grinding teeth were low-crowned and had each two simple1 transverse crests4 ,these grinding teeth and the lower tusks so resemble those of the ancestral ,proboscidea in the ,oligocene of ,egypt1 that the pyrotheres have actually been regarded as the beginnings of the mastodons and elephants1 but this is undoubtedly an error4 ,the ,astrapotheria1 another group which became extinct at or soon after the end of the ,santa ,cruz1 were relatively abundant in the ,deseado and counted some very large species4 ,finally1 the ,litopterna were represented by the same two families as continued through the ,pliocene and one of them far into the ,pleistocene4 ,the horse-like proterotheres were present1 but not enough of them has been obtained to show whether or not they were in a notably less advanced stage of development than those of the ,santa ,cruz4 ,the macrauchenids were quite similar to those of the latter formation1 though considerably smaller4 ,in addition1 there were a few genera1 survivals from earlier times1 which were not referable to either of these families4 ,the large number of genera1 especially among the toxodonts and typotheres1 which had high-crowned1 cement-covered teeth1 may be taken as an indication that grazing habits had already begun to be prevalent4 ,of this wonderful assemblage of hoofed animals1 divisible into six separate groups1 whether of ordinal or subordinal rank1 not a trace remains to-day4 ,not only are all the species1 genera and families extinct1 but the suborders and orders also4 ,further1 this was a very strictly autochthonous fauna1 so far as the hoofed animals were concerned1 and no member of any of the six groups has ever been found outside of the ,neotropical region4 #d4 ,eocene ,north ,america4--,in the western interior of ,north ,america the ,oligocene followed so gradually upon the ,eocene1 that there is great difficulty in demarcating them and much difference of opinion and practice obtains as to where the boundary line should be drawn4 ,not to depart too widely from the scheme used by ,professor ,osborn1 the ,uinta stage is here treated as uppermost ,eocene1 though this is a debatable procedure4 ,for several reasons1 the extraordinarily interesting and significant ,uinta fauna is far less completely known than that of the preceding ,bridger and succeeding ,white ,river stages4 ,for one thing1 it has been much less thoroughly explored1 and it may be confidently expected that future exploration will greatly enlarge our knowledge4 ,the smaller mammals of the ,uinta are particularly ill-known4 ,no ,insectivora have yet been found1 though this gap will assuredly be filled2 rodents are scanty in the collections and include only two families1 one the ischyromyids1 which were still common in the ,white ,river1 the other of doubtful position1 but not improbably to be considered as the beginning of the pocket-gophers 7,geomyid74 ,the archaic flesh-eaters1 or ,creodonta1 were represented by two families1 one comprising smaller animals with somewhat cat-like1 shearing teeth 7,oxynid71 the other1 very large beasts with crushing teeth 7,mesonychid71 neither of which continued into the ,white ,river4 ,as compared with the middle and lower ,eocene1 the creodonts had greatly diminished and1 to replace them1 the true ,carnivora were beginning to come in4 ,as yet1 however1 only small and very primitive dog-like forms are known and no trace of sabre-tooths or mustelines has been found4 ,indeed1 it is very doubtful whether members of these families ever will be found in the ,uinta1 for their presence in the succeeding ,white ,river was probably due to immigration4 ,the ,perissodactyla were the preponderant type of hoofed animals1 and ancestral forms of most of the ,white ,river genera have already been identified4 ,the titanotheres 7,diplacodon1 ,protitanotherium7 were much smaller and lighter than those of the lower ,white ,river and had much shorter horns4 ,the hyracodonts1 the lightly built1 cursorial rhinoceroses1 were represented by a genus 7,triplopus7 which was smaller and more slender than the ,white ,river form 7,hyracodon7 and its teeth were of distinctly more primitive character4 ,the heavy1 massive and presumably aquatic amynodonts 7,amynodon7 were likewise smaller and less specialized than their descendants of the ,oligocene4 ,no member of the true rhinoceros series has yet been identified in the ,uinta1 but there is some reason to think that they were nevertheless present4 ,tapirs are distinctly indicated by certain fossils1 but they are still too incompletely known to make possible any statement as to their degree of development4 ,the horses 7,epihippus71 like the other families mentioned1 were much smaller and distinctly more primitive than their successors in the ,oligocene4 ,the ,artiodactyla were1 for the first time in the history of ,north ,america1 as numerous and as varied as the perissodactyls and1 with the exception of the peccaries and anthracotheres1 representatives of all the ,white ,river families are known4 ,the finding of the peccaries is merely a question of further exploration1 but the anthracotheres were migrants from the ,old ,world1 and there is no likelihood that they will be discovered in the ,uinta at any future time4 ,fairly large1 pig-like animals1 probably referable to the giant-pigs or entelodonts1 occurred1 but nothing has yet been found which can be considered as the direct ancestor of the ,white ,river genus4 ,as was true of the perissodactyls1 the ,uinta artiodactyls were nearly all much smaller and more primitive than their ,oligocene descendants and the differences are most interesting from the evolutionary point of view4 ,the ancestral camel 7,protylopus7 was a little creature no bigger than a fox-terrier1 though the hypertragulids 7,leptotragulus7 were as large as ,leptomeryx and ,hypertragulus of the ,white ,river4 ,the most ancient known members of the oreodonts 7,protoreodon7 and the agriochrids 7,protagriochrus7 are found in the ,uinta4 ,the middle ,eocene fauna1 ,bridger stage1 though it passed upward very gradually into that of the ,uinta1 was yet1 on the whole1 very different from the latter4 ,it was exclusively indigenous and so radically distinct from the mammals of corresponding date in ,europe as to preclude the possibility of a land-bridge with that continent4 ,in the lower ,eocene1 as will be shown in a subsequent page1 the communication between the two continents was broadly open and the faunas of the two continents were much more closely similar than they have ever been since4 ,it is really remarkable to see with what comparative rapidity the two regions1 when severed1 developed different mammals under the operation of divergent evolution4 ,had the separation continued throughout the ,tertiary and ,quaternary periods1 ,north ,america would now have been as peculiar zologically as ,south ,america is1 a result which has been prevented by the repeated renewal of the connection4 ,the characteristic features of the ,bridger mammalian fauna were chiefly due to the great expansion and diversification of certain families1 which began their career at an earlier stage1 and to the disappearance of many archaic groups which had marked the more ancient faunas4 ,other archaic groups1 however1 survived and even flourished in the ,bridger1 and of these it is particularly difficult to convey a correct notion to the reader1 because they were so utterly unlike anything that now lives4 ,one of these orders1 the ,tniodontia1 which had so many points of resemblance to the ground-sloths that several writers have not hesitated to include them in the ,edentata1 survived only into the older ,bridger1 but the equally problematical ,tillodontia then reached their culmination1 though they were not very numerous4 ,though not at all related to that group1 the tillodonts looked like huge rodents1 with their chisel-like incisor teeth4 ,there was a remarkable assemblage of ,insectivora1 more numerous and varied than in any subsequent formation1 no less than six families being known4 ,one of these somewhat doubtfully represented the moles and two others modern ,asiatic groups4 ,the very unexpected discovery of an armadillo in the ,bridger has been reported1 but the propriety of referring this animal to the armadillos1 or even to the edentates1 has not yet been proved1 and it would therefore be premature to discuss its significance4 ,the only marsupials were opossums4 ,so far as our information extends1 there were no true ,carnivora in the ,bridger1 all the beasts of prey of the time belonging to the archaic ,creodonta1 which then reached their maximum development in numbers and diversity4 ,one family 7,oxynid7 included large and powerful flesh-eaters1 with cat-like dentition and short1 rounded1 lion-like heads1 long bodies and tails and short1 heavy limbs1 giving them the proportions of otters4 ,another 7the ,hynodontid7 comprised small1 long-headed1 fox-like and weasel-like animals1 which doubtless preyed upon small mammals and birds4 ,a third family 7,mesonychid7 was made up of moderate-sized1 long-jawed creatures1 which must have resembled1 rather remotely1 short-legged and long-tailed wolves and hyenas4 ,their habits and mode of life are somewhat problematical1 for their grinding teeth were blunt1 not adapted to the shearing of flesh1 and their claws were broad1 almost hoof-like4 ,such creatures could hardly have subsisted by the pursuit of living prey and were probably carrion-feeders and more or less omnivorous4 ,the ,miacid1 a family which connected the creodonts and true carnivores and might almost equally well be placed in either group1 were externally much like the small hynodonts1 but were more efficiently equipped for the capture and devouring of prey4 ,illustration3 ,,fig4 #aci4--;,a mesonychid creodont 7,dromocyon velox7 of the ,bridger stage4 ,restored from a skeleton in the ,museum of ,yale ,university4 ,of the archaic and extinct orders of hoofed animals1 the only one which persisted from earlier times into the ,bridger and greatly flourished there was the ,amblypoda1 one family of which 7,uintatheriid7 was preminently characteristic of middle ,eocene life1 becoming very rare and then dying out in the upper ,eocene4 ,the uintatheres of the ,bridger underwent considerable modification in size and appearance within the limits of the stage1 the larger and stranger species appearing toward the end of the time4 ,most of these great creatures may fairly be called gigantic1 for they equalled the largest modern rhinoceroses and smaller elephants in size4 ,the body1 limbs and feet were so elephantine in character that they were once believed to be ancestral ,proboscidea1 but the teeth and the fantastic skull were so radically different that this belief was long ago abandoned4 ,the upper canine teeth were converted1 in the males1 into formidable spear-like or scimitar-like tusks1 protected by great flange-shaped expansions of the lower jaw2 bony knobs on the end of the nose probably supported a pair of dermal horns like those of a rhinoceros and1 in addition1 a pair of high1 cylindrical1 horn-like1 bony protuberances arose above the eyes and another1 more massive pair1 near the back of the head4 ,it would be difficult to imagine more extraordinary creatures than the uintatheres1 which were the largest land-mammals of their time4 ,the family was entirely confined to ,north ,america1 no trace of them having been found in any other continent4 ,while the backward and archaic orders1 most of which have left no descendants in the modern world1 had thus a stately representation in ,bridger times1 they were outnumbered in genera1 species and individuals by the progressive orders1 which are still in more or less flourishing existence4 ,the ,primates1 whether lemurs or monkeys1 were numerous1 and this1 so far as is definitely known1 was their last appearance in extra-tropical ,north ,america4 ,they may at any time be found in the ,uinta1 but there is small probability that they will ever turn up in the ,white ,river or later formations4 ,the many rodents all belonged to the ischyromyids1 an extinct family which1 there is much reason to believe1 was ancestral to many families of the squirrel-like suborder of ,sciuromorpha4 ,most of them were species of a single genus 7,paramys7 and varied in size from a mouse to a beaver1 or even larger4 ,the ,perissodactyla may be said1 in one sense1 to have reached their culmination in the ,bridger2 not that many of them1 such as the horses and rhinoceroses1 did not advance far beyond their state of development in the ,eocene1 but at no subsequent time did the order as a whole possess such dominating importance4 ,there were five or six families of perissodactyls in the ,bridger1 and their remains are much the most abundant fossils found there4 ,individually1 the commonest perissodactyls of the time were the titanotheres1 of which there were several genera and many species1 differing chiefly in size and proportions1 though the largest hardly exceeded a modern tapir in stature and was not dissimilar in appearance4 ,these ,bridger titanotheres were considerably smaller than those of the ,uinta and therefore very much more so than the ,white ,river forms2 it was not till the latter stage that the family lived up to its name of 8titanic beasts40 ,by far the commonest of the genera in the middle and lower ,bridger was ,palosyops1 which was hornless1 while in the upper part of the beds are found genera 7e4g4 ,manteoceras and ,dolichorhinus7 in which the horns were just beginning to appear4 ,another extinct family1 the ,lophiodontid1 which was very abundant in the ,european ,eocene1 formed a very subordinate element in this fauna and included a number of small tapiroid genera 7e4g4 ,helaletes74 ,illustration3 ,,fig4 #adj4--,some characteristic mammals of the ,bridger ,eocene reduced to a uniform scale1 with a pointer dog1 in frame1 for comparison4 #a4 ,primitive rhinoceros 7,hyrachyus eximius74 #b4 ,tritemnodon agilis4 #c4 ,patriofelis ferox1 and #d1 ,dromocyon velox1 creodonts4 #e4 ,primitive rodent 7,paramys delicatior74 #f4 ,uintatherium alticeps4 #g4 ,titanothere 7,mesatirhinus superior74 ,the horses 7,orohippus7 were very small and primitive creatures1 no bigger than a fox1 with four toes in the front foot and three in the hind4 ,so completely different in appearance and proportions were these little animals from any of the modern horses1 that it requires an effort of the imagination to think of them as belonging to the same family1 and it is only by employing the family to designate a genetic series that such a classification can be justified4 ,the hyracodonts1 or cursorial rhinoceroses1 were very abundantly represented by a number of small and medium-sized animals 7,hyrachyus7 which had less specialized teeth1 shorter neck and limbs than their upper ,eocene and ,oligocene successors1 and four toes in the front foot2 one genus 7,colonoceras7 had a pair of nasal horns1 but would seem to have died out without leaving descendants4 ,in the upper part of the beds is found the ,uinta genus ,triplopus1 with three-toed fore foot2 and in the same division occurs another ,uinta genus1 ,amynodon1 the most ancient known species of the supposedly aquatic rhinoceroses4 ,true rhinoceroses1 that is animals which were directly ancestral to the modern members of the family1 have not been identified and may not have been present in ,north ,america2 that is still an open question4 ,tapirs1 all of them quite small1 were relatively common1 but are still very incompletely known4 ,the earliest known members of the clawed chalicotheres were of ,bridger date4 ,it is worth remarking that1 except a single genus in the upper and later portion of the stage 7,triplopus71 all of the ,bridger perissodactyls had four toes in the front foot and three in the hind1 while in the ,white ,river beds above the lowest substage the number three in both fore and hind feet was almost equally universal4 ,one of the most radical and striking differences between the ,uinta and ,bridger faunas was the rarity of ,artiodactyla in the latter1 which is in almost equally strong contrast with their abundance in the middle ,eocene of ,europe4 ,most significant of these rare ,bridger artiodactyls were the little creatures 7,homacodon71 hardly so large as a domestic cat1 which may fairly be regarded as a very early stage1 if not the actual beginning1 of the great camel family1 which was destined to play so conspicuous a part in the life of ,america1 ,north and ,south4 ,small pig-like animals 7,helohyus7 which were no doubt ancestral to the peccaries1 were fairly common and there were1 in addition1 relatively large animals 7,achnodon7 allied1 but not ancestral1 to the giant-pigs of the ,oligocene2 some of these were considerably larger than a full-grown ,wild ,boar 7,sus scrofa74 ,among all the many hoofed mammals of the ,uinta and ,bridger there was not a single one that had the high-crowned1 persistently growing teeth of the grazers2 all of them must have had browsing habits and have fed upon such soft vegetable tissue as did not rapidly abrade the teeth4 ,the same statement applies1 fortiori1 to the stages antecedent to the ,bridger and therefore to the entire ,eocene and ,paleocene4 ,from these facts it may be inferred that the grasses had not yet taken possession of wide areas4 ,concerning the ,bridger fauna1 ,professor ,osborn1 who has done so much to elucidate it1 says3 8,on the whole1 it is a very imposing1 diversified and well-balanced fauna1 with an equal distribution of arboreal1 cursorial1 aquatic1 fossorial1 carnivorous and herbivorous types40 ,the lower ,eocene is divisible into two stages1 in descending order1 the ,wind ,river and ,wasatch1 both extensively exposed in central ,wyoming4 ,as would be expected from its stratigraphical position1 the ,wind ,river fauna was largely transitional between that of the ,bridger above and that of the ,wasatch below4 ,unfortunately1 the fossils are far less numerous than those of the ,bridger and not so well preserved1 and therefore give us a less adequate conception of the life of that time4 ,the archaic1 non-progressive orders were strongly represented1 but already the progressive groups were in a numerical majority of species2 most of these archaic orders may be most advantageously described in connection with the ,wasatch4 ,opossums were almost certainly present1 though the available specimens are too fragmentary for assured determination4 ,the tillodonts1 tniodonts and insectivores differed little from the ,wasatch representatives of these orders1 except that the ,bridger tniodont1 ,stylinodon1 which had rootless1 persistently growing teeth1 was associated with the ,wasatch genus ,calamodon4 ,on the other hand1 the primitive flesh-eaters1 or creodonts1 which were referable to ,wasatch families1 were less numerous and varied and formed a mixture of ,bridger and ,wasatch genera4 ,the ,oxynid1 the family with cat-like teeth and head1 had both the smaller ,wasatch genus ,oxyna and the very large ,bridge ,patriofelis4 ,of the blunt-toothed ,mesonychid1 one very large animal 7,pachyna7 survived from the ,wasatch4 ,the small forms of the family ,hynodontid were common1 and there were numerous species of the progressive family ,miacid4 ,among the hoofed animals there were two of the antique orders which became extinct before the end of the ,eocene1 indeed1 one of these groups1 the ,condylarthra1 made its last appearance in the ,wind ,river4 ,this extremely primitive group1 which1 in a sense1 connected the hoofed with the clawed mammals1 will be described under the more ancient faunas4 ,the other order1 the ,amblypoda1 was represented by two very different families1 one of which1 the uintatheres1 was so flourishing in the ,bridger1 where it formed the most characteristic and by far the most striking element of the fauna4 ,the ,wind ,river genus 7,bathyopsis7 was a very much smaller animal than any of the ,bridger forms and its horn-like protuberances were in an incipient state1 while in various other respects it was decidedly more primitive than its successors4 ,the second family was represented by the genus ,coryphodon1 which did not survive into the ,bridger1 but was especially characteristic of the ,wasatch fauna1 with which it will be described4 ,turning now to the progressive orders1 we note that the rodents1 lemurs and monkeys were very similar to those of the ,bridger and belonged to the same families1 but were decidedly less numerous4 ,this difference1 however1 may be rather apparent than real and due to the much more favourable conditions for the preservation of small mammals in the middle ,eocene4 ,among the ,perissodactyla1 the horses were intermediate in size and structure between those of the ,bridger and those of the ,wasatch1 but were decidedly nearer to the latter4 ,the lophiodonts1 so far as known1 were represented by a single genus 7,heptodon7 which also occurred in the ,wasatch4 ,the modest beginnings of the titanotheres1 the family which became so very conspicuous in the middle and upper ,eocene and lowest ,oligocene1 may be noted in the ,wind ,river fauna1 in which there were two genera4 ,one of these 7,eotitanops71 the very probable ancestor of all the subsequent genera1 was quite small1 about two-thirds the size of a modern tapir1 while the other 7,lambdotherium7 was a much smaller1 lighter and more slender animal and apparently belonged to an abortive1 short-lived phylum4 ,then1 too1 the first of the hyracodonts1 or cursorial rhinoceroses1 made their appearance here in the genus ,hyrachyus1 which was afterward so common in the ,bridger4 ,no ,artiodactyla have yet been found in the ,wind ,river1 though there can be little doubt that they then inhabited ,north ,america1 as they did both before and afterward4 ,the ,wind ,river fauna was of so much less peculiar and isolated character than that of the ,bridger as to suggest a connection with the eastern hemisphere1 a suggestion which is strengthened by the unheralded appearance of the titanotheres and hyracodonts1 of which no forerunners have been found in the ,wasatch4 ,the lowest and most ancient of the ,eocene faunas is that of the ,wasatch formation1 which is extensively developed in central and southern ,wyoming1 ,utah and ,new ,mexico4 ,the fauna of this stage is plainly divisible into two groups3 7#a7 those types which were the descendants of ,american ,paleocene mammals and were therefore indigenous1 and 7#b7 the immigrants from other continents4 ,the indigenous mammals1 which almost all belonged to orders now extinct1 few of which survived later than the ,eocene1 must have given a very bizarre appearance to the assemblage1 especially as they were more numerous1 varied and1 for the most part1 larger and more conspicuous than the newcomers4 ,marsupials have not yet been found1 but the occurrence of opossums in the ,bridger and probably in the ,wind ,river gives some reason to believe that they were in ,north ,america during ,wasatch times also4 ,the ,tniodontia1 which bore a certain resemblance to ,south ,american edentates1 had one pair of incisor teeth above and below enlarged and chisel-shaped1 somewhat like those of rodents4 ,the ,tillodontia were much smaller than those of the ,bridger1 and their incisors were only beginning to take on the chisel-like form4 ,insectivora were quite abundant1 and three1 or perhaps four1 families were represented in the ,wasatch2 some of these resembled the modern aquatic insectivores of the west ,african rivers and others were more like ,european hedgehogs4 ,the flesh-eaters all belonged to the ,creodonta1 and1 though rather less diversified than those of the ,bridger1 were yet relatively abundant4 ,in size1 they ranged from little creatures not larger than a weasel up to truly enormous beasts1 and differed1 no doubt1 largely in habits and manner of life4 ,for the most part1 the families were the same as those of the ,bridger creodonts1 but the genera all were different4 ,the oxynids 7,oxyna7 were much smaller and lighter than the large and massive representatives found in the middle ,eocene1 and their teeth were not so cat-like4 ,another group of predaceous animals 7,palonictis7 which also inhabited ,europe1 but did not survive the lower ,eocene in either continent1 had short1 broad and very cat-like heads4 ,the mesonychids were far larger than those of the ,bridger1 a departure from the ordinary rule1 and the several species of the common ,wasatch genus 7,pachyna7 had grotesquely large heads4 ,a family 7,arctocyonid71 of very extensive geographical range and great antiquity1 had its last representatives here in a very curious animal 7,anacodon7 which had the flat-crowned1 tuberculated grinding teeth of the bears and the enlarged1 scimitar-like upper canines of the sabre-tooth cats4 ,such a combination seems utterly incongruous and no one would have ventured to predict it4 ,the progressive family of creodonts 7,miacid7 was already quite numerously represented1 but only by small forms1 which must have preyed upon small mammals1 birds and lizards4 ,two archaic orders of hoofed mammals were fairly numerous4 ,one1 the ,condylarthra1 comprised quite small1 five-toed animals1 with long tails and short feet and extremely primitive in structure4 ,a genus 7,phenacodus7 of this order was long regarded as being ancestral to most of the higher orders of ungulates1 but this belief has proved to be untenable4 ,more numerous were the ,amblypoda1 one genus of which 7,coryphodon71 though persisting into the ,wind ,river1 was especially characteristic of the ,wasatch4 ,the coryphodonts were the largest of lower ,eocene mammals1 and some of the species equalled a tapir or small rhinoceros in length and height1 but had heavier limbs2 as the skeleton conclusively shows1 these must have been heavy1 clumsy and exceptionally ugly brutes1 with formidable tusks1 large head1 but relatively more slender body1 short and massive limbs and elephantine feet4 ,in appearance1 these strange beasts were not altogether unlike the ,hippopotamus and were perhaps more or less amphibious in habits4 ,the other family of ,amblypoda1 the uintatheres1 have not yet been registered from the ,wasatch1 but they will undoubtedly be found there1 as they were unquestionably present at that time4 ,illustration3 ,,fig4 #ada4--,phenacodus primvus1 the best known ,wasatch representative of the ,condylarthra4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,illustration3 ,,fig4 #adb4--,the commonest of ,wasatch ungulates1 the amblypod1 ,coryphodon testis4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,all of the preceding groups were of the archaic1 non-progressive type and have long been extinct4 ,with the sole exception of one creodont family 7,miacid7 and perhaps some of the insectivores1 they have no descendants or representatives in the modern world4 ,all of them appear to have been indigenous and derived from ,north ,american ancestors1 though it is possible that a few were immigrants4 ,we now turn to the orders which were more significant of the future1 because they had within them the potency of a far higher development4 ,these progressive groups were all immigrants1 coming to ,north ,america from some region which cannot yet be positively identified1 but most probably was ,asia4 ,from the same region and at a corresponding period of time ,europe received many of the same forms1 and so many genera were at that time common to the latter continent and ,north ,america that a broad and easy way of intermigration must have been open4 ,one of these immigrant orders1 the ,rodentia1 the most ancient known members of which were these species from the ,north ,american ,wasatch1 was represented by the same family 7,ischyromyid7 and some of the same genera 7,paramys1 ,sciuravus7 as throve also in the ,bridger stage4 ,there were two orders of hoofed mammals1 which were newcomers to the western world1 ,perissodactyla and ,artiodactyla4 ,of the former was a genus 7,eohippus7 of the most ancient ,american horses4 ,these most interesting little animals1 no larger than small foxes and domestic cats1 would hardly be called horses1 were it not for the long series of gradual and successive modifications which led from ,eohippus up to the modern horses4 ,the graceful little creatures had a short neck1 curved back1 and relatively short1 slender limbs1 with four functional toes in the front foot and three in the hind2 and1 though they differed from existing horses in almost every detail of teeth and skeleton1 there was something unmistakably equine about them4 ,from the abundance of their remains it may be inferred that herds of them swarmed in the forests and glades of ,wasatch times4 ,the second perissodactyl family1 the ,lophiodontid1 which comprised considerably larger animals1 never attained to importance in ,america1 but flourished and became greatly diversified in ,europe4 ,what are believed to be the most ancient tapirs yet discovered 7,systemodon7 were individually very common in the ,wasatch4 ,this tapir was no larger than a ,coyote1 had no proboscis and was so little like a tapir in outward appearance that an observer might well be pardoned for overlooking the relationship2 even the skeleton is of so indifferent a character that the reference of this genus to the tapirs cannot be positively made4 ,of equal significance for the future was the arrival of the ,artiodactyla1 of which there were members of three families in the ,wasatch1 though individually they were much less common than the horses4 ,these were geologically the oldest known artiodactyls1 ,europe having yielded none of this date1 and are still too imperfectly known to justify any very positive statements about them4 ,one genus1 however 7,trigonolestes71 tiny little creatures1 like rabbits in size1 would seem to represent the beginnings of the great ruminant tribe1 now so very important a factor in the life of the world4 ,a second genus 7,eohyus71 considerably larger1 is very doubtfully referable to the pigs2 while a third 7,parahyus71 still larger1 was the first in the short-faced series of the entelodonts1 which persisted in ever increasing size through the whole ,eocene1 but could hardly have been ancestral to the true entelodonts1 or giant-pigs1 of the ,oligocene1 the place and time of whose origin are unknown4 ,another immigrant order of great interest1 since we ourselves belong to it1 the ,primates1 made its first appearance in ,north ,america in the ,wasatch1 but was not destined to long life or great importance in this continent1 where it did not survive the ,eocene4 ,several different kinds of small1 lemur-like and monkey-like creatures dwelt in the tree-tops of the ,wasatch forests4 ,one genus 7,anaptomorphus7 had a remarkable likeness to the modern ,tarsier 7,tarsius spectrum7 of the ,malay peninsula and islands4 ,south ,america4--,the ,eocene of ,south ,america1 referred by some writers to the upper ,cretaceous1 is very incompletely and unsatisfactorily known4 ,the ,casa ,mayor formation 7or ,notostylops ,beds71 which has yielded a great variety of mammals1 for the most part very fragmentary1 probably contains not one but several successive faunas which have not yet been fully discriminated1 and that of the next succeeding ,astraponotus ,beds is still but a scanty list4 ,this list1 however1 includes the most ancient glyptodonts yet discovered and the most ancient astrapotheres in the narrow sense of the term4 ,the ,astraponotus ,beds may be either ,eocene or ,oligocene in date4 ,taking the ,casa ,mayor faunas as a whole1 they were a very numerous and diversified assemblage of small mammals1 without a single large one among them4 ,there were no monkeys or rodents2 otherwise1 the orders were in almost all cases the same as those which made up the ,santa ,cruz fauna4 ,the marsupials were represented by the opossums and by several of the carnivorous kinds1 the only beasts of prey that ,south ,america had until the migrations from the north brought in the true ,carnivora1 late in the ,miocene or very early in the ,pliocene4 ,there were also numerous small marsupials of peculiar type1 of which the last living survivor is ,cnolestes1 of ,ecuador4 ,throughout the stage1 armadillos were present in considerable variety1 but are known only from the bony plates of the carapace1 and therefore little can be determined as to their relationships to the modern families4 ,only a single and very problematical genus of the ground-sloths1 which afterwards throve so mightily in the ,miocene and ,pliocene1 has been obtained and that in the later portion of the stage4 ,the orders of hoofed mammals were represented by many small animals1 most of which are known only from the teeth1 which show these ,casa ,mayor genera to have been far more primitive and less specialized than their descendants in the ,deseado and ,santa ,cruz stages4 ,all of them had the low-crowned grinding teeth of the browsers1 and no grazers were then in existence1 so far as is known4 ,no toxodonts1 in the more restricted sense of that term1 have been found1 but the two allied suborders of the ,typotheria and ,entelonychia were numerously represented4 ,of the former there were two families and of the latter three1 which is more than in the ,deseado or ,santa ,cruz formations4 ,one of the families of the ,entelonychia 7,notostylopid7 consisted of very small1 rodent-like animals1 with a pair of chisel-shaped incisors in upper and lower jaw1 and a second family 7,homalodontotheriid7 contained genera which would seem to have been directly ancestral to those of the ,santa ,cruz1 but were very much smaller than their successors4 ,the very large and massive ,pyrotheria of the ,deseado stage were represented by small animals1 in which the grinding teeth had two pairs of conical tubercles1 not yet united into transverse crests4 ,two families of the astrapotheres1 in the broad sense1 were far smaller than their ,oligocene and ,miocene descendants4 ,to the ,litopterna are referred a number of genera1 in which the grinding teeth were tuberculated and had very imperfectly developed crests1 so as strongly to suggest the teeth of the ,condylarthra4 ,however1 until something is ascertained regarding the skeleton1 especially the feet1 of these animals1 their relationships will remain more or less doubtful4 ,it will be observed that these ,casa ,mayor faunas not only were made up exclusively of small animals1 but also that they already were typically and characteristically ,south ,american and bore the stamp which remained essentially the same until the successive waves of migration from the north so greatly modified the composition of the ,neotropical fauna4 ,the absence of rodents and monkeys and the comparative unimportance of the ,edentata gave a somewhat different character to these ancient faunas from those of the ,santa ,cruz and later formations4 #e4 ,paleocene ,north ,america4--,a very important discovery is one lately made by ,american ,museum parties of a formation intermediate between the ,wasatch and ,torrejon4 ,the interesting fauna of these beds has not yet been described1 but it may be remarked that it contained none of the immigrant orders4 ,the vegetation of the ,paleocene was already very modern in character1 and nearly all of the common forest-trees were represented by species which differed but slightly from those of the present4 ,the grasses were already in existence1 but1 there is good reason to believe1 they had not attained to much importance and did not cover the plains and open spaces as they did in the ,miocene and still continue to do4 ,as the grasses afford the principal food-supply of so many grazing animals1 the matter of their abundance and extension is a very significant one in the history of mammalian development1 and1 as we have already learned1 eventually led to widespread and profound modifications of structure1 especially of the teeth4 ,while there is thus nothing very strange about the plant-world of ,paleocene times1 the higher animal life was almost totally different from that of modern times and made up a most curious and bizarre assemblage1 from which nearly all the familiar ,recent types were absent4 ,the reptiles had been greatly impoverished by the world-wide and1 as yet1 unexplained destruction which overtook them at the end of the ,mesozoic era1 but it is possible that in both ,north and ,south ,america a few of the huge ,dinosaurs survived the decimation of the class4 ,very characteristic of the ,paleocene in ,north ,america and ,europe were large1 lizard-like reptiles1 allied to the ,new ,zealand ,tuatara1 while crocodiles and tortoises abounded2 snakes were present1 but do not appear to have been very common4 ,it is the mammals which were the strangest element of ,paleocene life1 and our imaginary observer would find no creature that he had ever seen before4 ,the difference from modern mammalian life was not merely one of species1 genera or even families1 but of orders1 for only one1 or at most two1 of the orders now living were then to be found in ,north ,america1 and both of these 7marsupials and insectivores7 were primitive and archaic groups1 which seem like belated survivals in the modern world4 ,there were no rodents1 or true carnivores1 no lemurs1 monkeys1 artiodactyls1 perissodactyls or proboscideans4 ,in the ,torrejon1 or upper ,paleocene1 there were many herbivorous marsupials1 with very complex grinding teeth and chisel-like incisors1 but no carnivorous or insectivorous members of the order have been found4 ,insectivora were present4 ,of the creodonts1 or primitive flesh-eaters1 there were no less than five families2 the bear-like ,arctocyonid1 which died out in the ,wasatch1 were quite numerous1 and the problematical ,mesonychid were much smaller and more primitive mammals than those of the ,eocene4 ,passing over two families which did not survive the ,torrejon1 we may note the first of the ,miacid1 the progressive family which led eventually to the true ,carnivora4 ,the hoofed animals all belonged to the archaic ,condylarthra and ,amblypoda2 of the former there were many genera and species referable to three families1 one of which contained the forerunners of the ,wasatch ,phenacodus4 ,the genus ,pantolambda of the ,amblypoda may well have been ancestral to both the coryphodonts and the uintatheres of the ,eocene4 ,illustration3 ,,fig4 #adc4--,the ,torrejon forerunner 7,pantolambda bathmodon7 of ,coryphodon4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,the ,puerco fauna was much like that of the ,torrejon1 but even less advanced and diversified4 ,the herbivorous marsupials were more abundant1 and some of them 7,polymastodon7 larger than those of the ,torrejon2 ,insectivora may have been present1 but this is doubtful4 ,the creodonts1 so far as they have been discovered1 were less numerous1 varied and specialized than those of the ,torrejon and included but one of the families which passed over into the ,eocene4 ,the ,condylarthra were much less common and the ,amblypoda but doubtfully represented1 but the edentate-like ,tniodontia were conspicuous4 ,illustration3 ,,fig4 #add4--;,head of an allotherian marsupial 7,polymastodon taensis7 from the ,puerco stage4 ,restored from a skull in the ,american ,museum of ,natural ,history4 ,not only were the ,paleocene faunas radically different from the mammals of our time1 but they could not have been ancestral to the latter1 being hardly more than an advanced and diversified ,mesozoic assemblage4 ,it is true that some of its elements1 such as the ,condylarthra1 ,amblypoda and ,creodonta1 developed greatly and played an important part in the life of the ,eocene1 but of these only a few creodonts continued into the ,oligocene and all became extinct without leaving any descendants behind them4 ,another curious fact concerning the ,paleocene mammalian faunas is that they were made up entirely of small and very small animals2 not a single mammal as large as a sheep has yet been found in these beds1 and the same is true of ,europe4 ,that a land-connection with the ,old ,world existed during the ,paleocene epoch1 is indicated by the similarity of the faunas of ,north ,america and ,europe4 ,,chapter ,,viii ,,history ,,of ,,the ,,perissodactyla ,in attempting to trace the evolutionary history of the various mammalian groups1 it is necessary to bear in mind the inevitable limitations of work of this kind4 ,speaking of plants1 ,dr4 ,d4 ,h4 ,scott says3 8,our ideas of the course of descent must of necessity be diagrammatic2 the process1 as it actually went on1 during ages of inconceivable duration1 was doubtless infinitely too complex for the mind to grasp1 even were the whole evidence lying open before us4 ,we see an illustration1 on a small scale1 of the complexity of the problem1 in the case of domesticated forms1 evolved under the influence of man4 ,though we know that our cultivated plants1 for instance1 have been developed from wild species within the human period1 and often within quite recent years1 yet nothing is more difficult than to trace1 in any given instance1 the true history of a field-crop or garden plant1 or even1 in many cases1 to fix its origin with certainty40#e ,with some mammalian groups the task1 though difficult enough1 is not so hopeless1 because of more complete records1 yet in dealing with mammals a very troublesome complication is introduced by the existence within the families1 and even within the genera1 of two or more parallel phyla1 or genetic series4 ,without complete and perfect material it is impossible to make sure that we are not confusing the different phyla with one another and placing in one series species and genera that properly belong in a different one4 ,thus1 ,osborn distinguishes no less than seven such phyla among the true rhinoceroses of the ,old and ,new ,worlds1 which long followed parallel1 but quite independent1 courses of development1 and five phyla among the ,american horses4 ,while these phyla add so much to the difficulty of working out the genealogical series1 it is possible to simplify the problem and treat it in a broad and comprehensive manner that will sufficiently establish the essential steps of change4 ,illustration3 ,,fig4 #ade4--,left manus of ,tapir 7,tapirus terrestris74 ,s41 scaphoid4 ,l41 lunar4 ,py41 pyramidal4 ,pis41 pisiform4 ,td41 trapezoid4 ,m41 magnum4 ,un41 unciform4 ,the metacarpals are erroneously numbered4 ,mc4 ,i41 second metacarpal4 ,mc4 ,,ii41 third do4 ,mc4 ,,iii41 fourth do4 ,mc4 ,,iv41 fifth do4 ,ph4 #a1 first phalanx4 ,ph4 #b1 second do4 ,ung41 ungual phalanx4 ,in external appearance and general proportions the different families of existing perissodactyls have very little in common2 that tapirs and rhinoceroses should be related is not surprising1 but the horses would seem to be as far removed from both of the former as possible4 ,why1 then1 should they be included in the same order8 ,a study of the skeleton1 however1 reveals the community of structure which obtains between the three families1 a community which removes them widely from all other hoofed mammals4 ,in all existing perissodactyls1 though not in most of the ,eocene genera1 all the premolars1 except the first1 have the size and pattern of the molars4 ,the foramina of the skull1 or perforations by which blood-vessels and nerves enter and leave the cranium1 are arranged in a way characteristic of the order and different from that seen in other hoofed mammals4 ,the femur always has the third trochanter4 ,the number of digits in each foot is usually odd1 #a1 #c or #e1 but four-toed forms occur1 as the tapirs1 which have four toes in the front foot1 three in the hind2 the important character is that the median plane of the foot bisects the third digit1 which is symmetrical4 ,the third and fourth1 each asymmetrical1 together form a symmetrical pair4 ,especially characteristic is the form of the astragalus and calcaneum 7ankle and heel bones72 the astragalus has but a single1 deeply grooved and pulley-like surface1 that for the tibia1 the lower end is nearly flat and rests almost entirely upon the navicular1 covering but little of the cuboid 7see ,figs4 #adf1 #adh74 ,the calcaneum does not articulate with the fibula and its lower end is broad and covers most of the cuboid4 ,while the foregoing list includes the most important of the structural features which are common to all perissodactyls and differentiate them from other hoofed animals1 there are many others which it is needless to enumerate4 ,illustration3 ,,fig4 #adf4--,left pes of ,tapir4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cn4 #a1 ,cn4 #b1 ,cn4 #c1 first1 second and third cuneiforms4 ,mr4 ,,ii1 ,,iii1 ,,iv1 second1 third and fourth metatarsals4 ,the subjoined table gives the families and principal genera of the ,american ,perissodactyla2 extinct groups are marked 4 ,suborder ,,chelodactyla4 ,normal ,perissodactyls ,i4 ,,equid4 ,horses4 ,eohippus1 low4 ,eoc4 ,orohippus1 mid4 ,eoc4 ,epihippus1 up4 ,eoc4 ,mesohippus1 low4 ,oligo4 ,miohippus1 up4 ,oligo4 ,anchitherium1 up4 ,oligo4 ,parahippus1 low4 ,mioc4 to low4 ,plioc4 ,desmatippus1 mid4 ,mioc4 ,hypohippus1 mid4 ,mioc4 to low4 ,plioc4 ,merychippus1 mid4 ,mioc4 to low4 ,plioc4 ,protohippus1 up4 ,mioc4 ,pliohippus1 up4 ,mioc4 and low4 ,plioc4 ,neohipparion1 up4 ,mioc4 and low4 ,plioc4 ,hipparion1 ,plioc4 ,hippidion1 ,pleist41 ,s4 ,amer4 ,hyperhippidium1 ,pleist41 ,s4 ,am4 ,equus1 ,pleist41 ,n4 and ,s4 ,amer4 ,,ii4 ,,titanotheriid4 ,titanotheres4 ,lambdotherium1 low4 ,eoc4 ,eotitanops1 low4 ,eoc4 ,palosyops1 mid4 ,eoc4 ,telmatherium1 mid4 ,eoc4 ,dolichorhinus1 up4 ,eoc4 ,diplacodon1 up4 ,eoc4 ,titanotherium1 low4 ,oligo4 ,,iii4 ,,tapirid4 ,tapirs4 ,systemodon1 low4 ,eoc4 ,isectolophus1 mid4 and up4 ,eoc4 ,protapirus1 ,oligo4 ,tapiravus1 mid4 ,mioc4 ,tapirus1 ,pleist41 ,n4 ,amer41 ,pleist4 and ,recent1 ,s4 ,amer4 ,,iv4 ,,lophiodontid4 ,lophiodonts4 ,heptodon1 low4 ,eoc4 ,helaletes1 mid4 ,eoc4 ,colodon1 low4 ,oligo4 ,v4 ,,rhinocerotid4 ,true ,rhinoceroses4 ,trigonias1 low4 ,oligo4 ,cnopus1 ,oligo4 and low4 ,mioc4 ,diceratherium1 up4 ,oligo4 and low4 ,mioc4 ,aphelops1 mid4 ,mioc4 to low4 ,plioc4 ,teleoceras1 mid4 ,mioc4 to low4 ,plioc4 ,,vi4 ,,hyracodontid4 ,hyracodonts and ,amynodonts1 cursorial and aquatic ,rhinoceroses4 ,hyrachyus1 low4 and mid4 ,eoc4 ,triplopus1 mid4 and up4 ,eoc4 ,colonoceras1 mid4 ,eoc4 ,hyracodon1 low4 ,oligo4 ,amynodon1 up4 ,eoc4 ,metamynodon1 low4 ,oligo4 ,suborder ,,ancylopoda4 ,clawed ,perissodactyls ,,vii4 ,,chalicotheriid4 ,chalicotheres4 ,moropus1 up4 ,oligo4 and low4 ,mioc4 8,schizotherium1 low4 ,oligo4 ,eomoropus1 mid4 ,eoc4 ,the earliest perissodactyls of which we have any knowledge are found in the older part of the lower ,eocene 7,wasatch stage7 of ,europe and ,north ,america1 into which they must have migrated from some other region yet unknown1 for no probable ancestors of the group are found in the ,paleocene of either continent4 ,i4 ,,suborder ,,chelodactyla4 ,,normal ,,perissodactyla4 #a4 ,equid4 ,horses ,in order to make intelligible the evolutionary changes which have led up to the modern horses1 it will be necessary to say something concerning the dental and skeletal features which characterize these animals4 ,using the term horses in a broad sense to include all the existing members of the family ,equid1 true horses1 asses1 zebras and quaggas1 we find a greater uniformity in the skeleton and teeth than would be expected from the external appearance4 ,the differences in appearance are1 however1 largely due to colouring1 growth of mane and tail and the size of the ears1 which leave no record in the skeleton4 ,illustration3 ,,fig4 #adg4--;,asiatic ,wild ,horse 7,equus przewalskii74--,by permission of the ,n4,y4 ,zolog4 ,soc4 ,the teeth 7,figs4 #de1 p4 #ie2 #aed1 p4 #cjf7 are extremely high-crowned1 or hypsodont1 and do not form roots till an advanced age2 the incisors have a deep1 enamel-lined pit1 the 8mark0 in the centre of the grinding surface2 the first premolar in each jaw is very small and of no functional importance2 the other premolars have the same pattern as the molars1 which is excessively complex in the arrangement of the enamel ridges and the areas of dentine and cement4 ,the skull 7,fig4 #aed1 p4 #cjf7 is long1 especially the facial portion1 the eye-socket 7orbit7 being shifted behind the teeth1 which otherwise1 on account of their great height1 would press upon the eye itself2 the orbit is completely encircled in bone4 ,the lower jaw is deep vertically and the ascending ramus 7see p4 #ff7 very high1 on account of the hypsodont character of the teeth1 which thus necessitates a remodelling of the skull in several respects4 ,the neck is long1 each of its seven vertebr being elongate2 except in the atlas and axis1 the anterior face of each centrum is strongly convex and the posterior of all except the atlas is deeply concave2 the odontoid process of the axis 7see p4 #ga7 is spout-shaped1 concave on the upper and convex on the lower side1 lodging and protecting the spinal cord4 ,the spines of the anterior dorsal vertebr are very high1 making a low hump at the withers between the shoulder-blades2 the trunk-vertebr are so arranged as to make the back almost straight and horizontal4 ,the limbs and especially the feet are very long4 ,the two bones of the fore-arm1 the ulna and radius1 are cossified into a single piece 7,fig4 #cj1 p4 #ha71 but the limits of each are still plainly to be seen1 especially in a young animal2 and it is evident that the ulna is greatly reduced in size and has lost its middle portion1 while all the weight is borne by the radius4 ,similarly1 in the hind leg the enlarged tibia1 or shin-bone1 alone supports the weight2 and only the two ends of the fibula are preserved 7,fig4 #ch1 p4 #hg71 and these are indistinguishably fused with the tibia in the adult animal1 but may be made out in the colt4 ,the thigh-bone has a very characteristic shape1 which is difficult to describe without an undue use of technical terms1 but the unusual prominence of the great trochanter 7,fig4 #ce1 p4 #he7 and of the rotular groove is an important factor in producing this appearance4 ,illustration3 ,,fig4 #adh4--,left pes of ,horse4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cn4 #c1 third cuneiform4 ,mt4 ,,iii1 functional 7third7 metatarsal4 ,mt4 ,,ii and ,mt4 ,,iv1 splints4 ,illustration3 ,,fig4 #adi4--,left manus of ,horse1 front side2 to the right1 rear view of the metacarpus4 ,s41 scaphoid4 ,l41 lunar4 ,py41 pyramidal4 ,pis41 pisiform4 ,td41 trapezoid4 ,m41 magnum4 ,u41 unciform4 ,mc4 ,,ii1 ,mc4 ,,iv1 rudimentary second and fourth metacarpals1 or splints4 ,the very long and slender feet are so raised from the ground that the animal walks upon the very tips of the toes1 the wrist being what horsemen call the 8knee0 and the heel is the 8hock10 and the gait is thoroughly unguligrade4 ,each foot has but a single functional toe1 the third or middle one of the primitive five-toed foot2 and1 as this toe has to carry the whole weight supported by its leg1 it is necessarily much larger than in animals which distribute the weight among several digits4 ,the horses are therefore said to be monodactyl1 or single-toed1 but the term is not strictly accurate1 for on each side of the functional digit is a rudimentary or vestigial one1 the #b;d and #dth of the original five4 ,these rudimentary digits1 which are not visible externally1 have no phalanges and are merely 8splint-bones10 metapodials 7see p4 #ij7 which have very slender shafts and end below in blunt points4 ,the single functional metapodial has encircling its lower articular end a prominent ridge or keel1 which fits into a corresponding groove on the upper end of the first phalanx and serves to prevent lateral dislocation4 ,in most mammals this keel is merely a projection from the lower articular surface and is confined to the posterior side1 so as not to be visible from the front4 ,the terminal or ungual phalanx is much enlarged to carry the great weight which it supports and is enclosed in the characteristic hoof1 unlike that of any other mammal4 ,in brief1 the whole structure of the horses is pre-eminently adapted to swift running2 they are admirable 8cursorial machines10 as they have been called1 and every part of the skeleton has been modified and specialized to that end2 the narrow1 rigid hoofs fit them for walking on firm ground and they speedily are made helpless in quicksand or bog4 ,did we know nothing of their mode of life1 we might confidently infer from their teeth that the horses were grazers1 feeding principally upon grass4 ,a long-legged1 grazing animal must needs have a neck of sufficient length to enable the mouth to reach the ground easily1 unless a long proboscis is developed2 and so we shall find in the history of the horses that the elongation of the head and neck kept pace with the lengthening of the legs and feet4 ,though it can hardly be doubted that the horses passed through most of their development in ,north ,america1 yet the immediate ancestry of all the existing species must be sought in the ,old ,world1 none of the many ,pleistocene species of the western hemisphere having left any descendants4 ,in ,north ,america all of the known ,pleistocene forms belonged to the genus ,equus1 but the ,true ,horse1 ,e4 caballus1 was not among them4 ,the more abundant and important of these species have been sufficiently described in ,chapter ,,vii 7p4 #aii72 it need only be recalled that there were ten or more distinct forms1 ranging in size from the great ,e4 giganteus of ,texas to the minute ,e4 tau of ,mexico1 while the plains and forests were the feeding grounds of moderate-sized species1 about #ad hands high4 ,in the latest ,pliocene1 and no doubt earlier1 species of the modern genus ,equus had already come into existence2 and in association with these1 at least in ,florida1 were the last survivors of the three-toed horses which were so characteristic of the early ,pliocene and the ,miocene4 ,however1 little is known about those earliest recorded ,american species of ,equus1 for the material so far obtained is very fragmentary4 ,in the absence of any richly fossiliferous beds of the upper ,pliocene generally1 there is a painfully felt hiatus in the genealogy of the horses2 and it is impossible to say1 from present knowledge1 whether all of the many species of horses which inhabited ,north ,america in the ,pleistocene were autochthonous1 derived from a purely ,american ancestry1 or how large a proportion of them were migrants from the ,old ,world1 coming in when so many of the ,pleistocene immigrants of other groups arrived4 ,it is even possible1 though not in the least likely1 that all of the native ,american stocks became extinct in the upper ,pliocene and that the ,pleistocene species were all immigrants from the eastern hemisphere1 or the slightly modified descendants of such immigrants2 but1 on the other hand1 it is altogether probable that some of these numerous species were intruders4 ,unfortunately we are in no position yet to distinguish the native from the foreign stocks4 ,in the middle ,pliocene1 which also has preserved but a meagre and scanty record of its mammalian life1 we again meet with horses in relative abundance1 but of a far more primitive type4 ,they are still incompletely known1 but it is clear that they belonged to three parallel series1 or phyla1 of three-toed grazing horses1 with teeth which1 though high-crowned1 had not attained to the extreme degree of hypsodontism seen in the species of ,equus and had a somewhat less complex pattern of the grinding surface1 though distinctly foreshadowing the modern degree of complication4 ,one of the genera 7,pliohippus7 was not improbably the ancestor of a very peculiar horse 7,hippidion7 of the ,south ,american ,pleistocene4 ,these middle ,pliocene genera were much smaller animals than the ,pleistocene horses1 aside from the pygmy species of the latter1 of light and more deer-like proportions1 and with three functional toes or digits4 ,the median digit 7#c;d of the original five7 was much the largest and carried most of the weight1 on hard ground practically all of it2 the lateral digits 7#b;d and #dth7 which in existing horses are represented by the rudimentary metapodials1 or 8splints10 though much more slender than the median digit1 yet had the complete number of parts and each carried a small hoof4 ,mere 8dew-claws0 as these lateral toes were1 they may have been of service in helping to support the weight in mud or snow4 ,in all parts of the skeleton there are little details which show that these species of the middle ,pliocene were not so advanced and differentiated as are their modern successors1 but it would be unprofitable to enumerate these details1 which are of interest only to the anatomist4 ,in the lower ,pliocene the horses were very much more numerous and varied than in the middle portion of the epoch4 ,the same three genera of grazing animals1 represented by less advanced and modernized species1 are found2 and1 in addition1 there was an interesting survival 7,merychippus7 from the middle ,miocene of an intermediate type1 together with several species of browsing horses 7,parahippus and ,hypohippus74 ,in these browsing forms the teeth were all low-crowned and early formed their roots1 and the crowns were either without cement or with merely a thin film of it in the depressions of the grinding surface4 ,the pattern of the grinding surface is so very much simpler than in the high-crowned1 prismatic teeth of the grazers that it requires close analysis to detect the fundamental identity of plan4 ,such teeth imply that their possessors must have fed habitually upon a softer and less abrasive diet than grass1 probably the leaves and soft shoots of trees and bushes and other succulent vegetable substances1 very much in the fashion of existing deer1 and must therefore have been chiefly inhabitants of the woods and groves and thickets along streams1 as the grazing species were of the plains and open spaces4 8,this assemblage of the progressive and conservative types of horses was certainly one of the most distinctive features of ,lower ,pliocene time in ,north ,america0 7,osborn74 ,illustration3 ,,fig4 #aej4--,three-toed1 grazing horse 7,neohipparion whitneyi7 of the upper ,miocene4 ,restored from skeletons in the ,american ,museum of ,natural ,history4 ,in the upper ,miocene very much the same conditions prevailed and1 for the most part1 the same genera of horses1 with different and somewhat less advanced species1 were found as in the lower ,pliocene1 so that no particular account of them is needed4 ,in the middle ,miocene1 however1 there was a change1 the typically grazing horses being very rare or absent and those with intermediate forms of teeth taking their place4 ,evidently1 it was about this time that the horses with more plastic organization and capable of readjustment to radically different conditions began to take to the grazing habit1 while other phyla1 less capable of advance1 retained the ancient1 low-crowned type of grinding teeth and1 after persisting1 as we have seen1 into the lower ,pliocene1 became extinct before the middle of that epoch4 ,it is of great interest to observe that in the genus 7,merychippus7 intermediate between the browsing and grazing types1 the milk-teeth retained the older and more primitive character of low crowns without covering of cement1 while the permanent grinders had much higher1 cement-covered and complex crowns4 ,in the lower ,miocene1 the variety of horses was much diminished and all had the low-crowned1 cement-free1 browsing type of teeth4 ,reversing the statement1 we see that in the middle and still more in the upper ,miocene the primitive and more or less distinctly homogeneous phylum branched out into several series1 like a tree1 some of the branches continuing and further subdividing through the ,pliocene and ,pleistocene1 while others1 less progressive and less adaptable1 underwent but little change and had died out before the middle ,pliocene4 ,illustration3 ,,fig4 #aea4--,skeleton of ,neohipparion whitneyi1 ,american ,museum4 ,the ,oligocene horses deserve more particular attention1 for they were almost the half-way stage of development in the long backward ascent to the earliest known members of the family in the lower ,eocene4 ,we may pass over the ,john ,day horses 7,miohippus71 which were somewhat larger than those of the ,white ,river1 but otherwise very like them1 merely noting the presence of a slightly different genus 7,anchitherium7 which was the probable ancestor of ,hypohippus and the other non-progressive types of the ,miocene and ,pliocene4 ,the genus 7,mesohippus7 which characterizes the ,white ,river1 or lower ,oligocene1 was a group of species of different sizes1 becoming smaller as we go back in time1 the commonest one being considerably smaller than a sheep and differing more or less in all its parts from the horses of the upper ,miocene and all subsequent formations4 ,the teeth were very low-crowned and fitted only for the mastication of soft vegetable tissue2 but it is of particular interest to observe the beginnings of the 8mark0 in the upper incisors in the form of a low enamel-ridge arising behind the cutting edge of the tooth2 the lower incisors still had the simple chisel-like crowns of the more ancient genera2 all the premolars1 except the first1 had already acquired the molar-pattern4 ,illustration3 ,,fig4 #aeb4--,the small1 browsing1 three-toed1 short-necked horse 7,mesohippus bairdi7 of the middle ,white ,river4 ,restored from a skeleton in the ,american ,museum4 ,the skull resembled that of a very small modern horse1 but with many differences of detail1 the most obvious of which is the shallowness of the jaws1 for depth was not needed to carry the very low-crowned teeth1 and1 for the same reason1 the ascending ramus of the lower jaw was short4 ,the face was relatively short and the eye-socket1 which was incompletely surrounded by bone1 was directly above the hindmost teeth2 the cranium was proportionately large and capacious and the brain1 as is shown by the cast1 was richly convoluted4 ,the neck was relatively far shorter than in the ,miocene genera1 the ball-and-socket joints between its successive vertebr were less elaborated and the odontoid process of the axis was in the first stage of assuming the spout-like form1 being semicylindrical1 with convex lower and flat upper surface4 ,the trunk was proportionately long and the back sloped forward1 owing to the greater length of the hind legs4 ,the limbs and feet were elongate and very slender1 but the fore-arm bones are only partially cossified1 and the ulna1 though greatly attenuated1 was still complete4 ,the same is true of the bones of the lower leg2 the shaft of the fibula was hardly more than a thread of bone1 but its full length was preserved4 ,in the fore foot there were three functional digits1 the median one enlarged and supporting most of the weight1 but its hoof was much thinner and flatter than in the corresponding digit in the ,miocene and subsequent genera2 the lateral digits touched the ground and were not entirely functionless and1 in addition1 there was a small splint1 the rudiment of the fifth digit4 ,the hind foot was three-toed1 without splint4 ,the little ,uinta horse 7,epihippus7 is still very incompletely known1 but gives us one point at least of greater primitiveness than the ,white ,river genus in that only the last two premolars had taken on the molar-pattern1 the forward two being smaller and simpler4 ,the known species of the ,uinta genus was very much smaller than any of the ,white ,river forms and even smaller than some of those of the preceding ,bridger formation2 but it should be remembered that the ,uinta has been but partially explored and much remains to be learned regarding its fauna4 ,the ,bridger horses are fortunately much better known4 ,there are several species of the genus ,orohippus1 which form a connected and progressive series2 and1 though much smaller than the smallest and oldest of the ,white ,river forms1 they were somewhat larger than the known representative of the ,uinta1 ,epihippus1 but distinctly more primitive in all other respects4 ,the incisors were simple cutting teeth1 with no trace of even an incipient 8mark10 and only one premolar in each jaw1 the hindmost one1 had taken on the molar-pattern4 ,the orbit was farther forward in the skull and less enclosed behind than in ,mesohippus1 the cranium narrower and less capacious2 the neck was even shorter and the odontoid process of the axis still retained the primitive peg-like form4 ,the limbs and feet were conspicuously shorter in proportion than those of the ,white ,river genus2 the ulna and fibula were stouter and less reduced and entirely separate from the radius and tibia respectively4 ,the front foot had four functional toes2 the fifth digit1 which in ,mesohippus had been reduced to a splint1 was completely developed in the ,bridger horses1 but the hind foot was three-toed4 ,illustration3 ,,fig4 #aec4--,the 8,dawn ,horse0 7,eohippus7 of the lower ,eocene4 ,restored from a skeleton in the ,american ,museum4 ,passing over1 for lack of space1 the transitional forms of the ,wind ,river1 we come finally to the most ancient known horses1 the ,wasatch species comprised in the genus ,eohippus1 the 8,dawn ,horse10 as its name signifies2 these were little creatures ranging in size from a cat to a small fox4 ,despite an unmistakably equine look in the skeletons of these diminutive animals1 it is only the long intermediate series of species and genera1 together forming a closely linked chain1 which we have traced back from the ,pleistocene to the lower ,eocene1 that leads us to regard ,eohippus as the ancestral type of the horses4 ,were only the two ends of the chain known1 he would be a daring speculator who should venture to connect them4 ,in these little ,wasatch horses we have the evidence of a still more ancient form with five fully developed toes in each foot1 since the front foot had four functional digits and indication of a splint1 and splints1 as the whole history of the long series teaches1 always are found to be functional digits in the ancestor2 the hind foot had three toes and perhaps two splints4 ,this preceding form is hardly to be looked for in ,america or ,europe2 it will be found1 if ever1 in the region whence the great migration came4 ,in all other respects1 as well1 ,eohippus was what we should expect the forerunner of the ,wind ,river and ,bridger horses to be4 ,the premolars were all smaller and simpler than the molars and the latter in the upper jaw are particularly interesting1 for they had no crests and ridges of enamel1 but four principal conical cusps1 arranged in two transverse pairs1 and between the cusps of each pair was a tiny cuspule no bigger than the head of a pin4 ,these cuspules were the first step in the formation of the transverse crests1 which were destined to assume such importance in the subsequent members of the series4 ,the neck was very short1 the body long1 with curved or arched back1 the limbs and feet short1 and the hind limb much longer than the fore1 making the relative proportions of the various parts of the skeleton very different from what they afterwards became4 ,reviewing this marvellous history of steady and long-continued change1 beginning with the most ancient genus1 ,eohippus1 the following modifications may be noted3 7#a7 ,there was a nearly constant1 if somewhat fluctuating1 increase in size1 leading by slow gradations from the diminutive horses of the lower ,eocene to the great animals of the ,pleistocene4 7#b7 ,the molar teeth1 originally made up of conical cusps1 changed to a highly complex pattern of crests and ridges1 and the premolars1 one by one1 assumed the size and pattern of the molars2 the low-crowned1 rooted and cement-free teeth1 fitted only for browsing1 became very high-crowned1 prismatic and cement-covered1 admirably adapted to grazing4 ,beginning in the upper incisors of the ,white ,river ,mesohippus1 the 8mark0 became established as an enamel-lined pit1 growing in depth as the teeth increased their length4 7#c7 ,the face grew relatively longer1 the eye-socket being shifted behind the teeth and becoming completely encircled in bone1 and the jaws were greatly increased in depth to accommodate the very long teeth4 7#d7 ,the short neck was greatly elongated and the individual vertebr modified so as to give flexibility with no loss of strength4 ,the primitive peg-like odontoid process of the axis became first semicylindrical and then spout-shaped4 7#e7 ,the arched back was straightened and the neural spines1 especially of the anterior dorsals1 elongated4 7#f7 ,the limbs grew relatively much longer2 the bones of the fore-arm and lower leg were fused together1 the one on the inner side 7radius and tibia7 enlarging to carry the entire weight and the external one 7ulna and fibula7 becoming more or less atrophied4 ,illustration3 ,,fig4 #aed4--,series of horse skulls in ascending geological order4 ,a41 ,eohippus1 lower ,eocene 7after ,cope74 ,b41 ,mesohippus1 lower and middle ,oligocene4 ,c41 ,protohippus1 upper ,miocene 7after ,cope74 ,d41 ,equus4 ,illustration3 ,,fig4 #aee4--,right manus and left pes of ,equus4 ,illustration3 ,,fig4 #aef4--,right manus and left pes of ,protohippus4 7#g7 ,the feet were much elongated and the median 7#c;d7 digit of each gradually enlarged until it carried the whole weight1 at the same time modifying the shape of the hoof so as to fit it to be the sole support of the body4 ,the other toes gradually dwindled and became functionless1 though often retained as splints4 ,the first digit 7pollex and hallux7 was first lost1 then the fifth1 then the second and fourth were reduced to dew-claws and finally to splints4 ,thus the pentadactyl horses of the lower ,eocene were transformed into the monodactyl species of the ,pliocene and ,pleistocene4 ,in ,south ,america the story of the horses was a brief one1 for they were among the immigrants from the north and did not reach the southern continent till the ,pliocene1 probably late in that epoch1 for none of the three-toed genera have been found in ,south ,america4 ,so far as known1 these southern equines were small and medium sized animals1 with large heads1 relatively short feet and somewhat ass-like proportions4 ,there were two well-defined groups of these animals3 7#a7 species of the genus ,equus1 which thus1 at one time or another1 inhabited every one of the continents1 ,australia excepted2 7#b7 three genera peculiar to ,south ,america and developed there from northern ancestors1 probably ,pliohippus4 ,two of these genera 7,hippidion and ,onohippidium7 displayed curious modifications of the nasal bones1 which were extremely slender and attached to the skull only at their hinder ends1 instead of being1 as is normally the case1 supported for nearly their whole length by lateral articulation with other bones4 ,what can have been the significance and function of these excessively slender1 splint-like nasals1 it is difficult to conjecture4 ,the third genus 7,hyperhippidium7 was a small mountain-horse1 with extremely short feet1 which were well adapted to climbing4 ,illustration3 ,,fig4 #aeg4--,right manus and left pes of ,mesohippus4 ,illustration3 ,,fig4 #aeh4--,right manus and pes of ,eohippus4 ,this is the merest outline sketch of a most wonderful series of gradual and progressive modifications1 a sketch that might readily be expanded into a volume1 were all the details filled in4 ,while each set of organs1 teeth1 skull1 neck1 body1 limbs and feet1 might appear to advance independently of the others1 in reality there was no such independence1 for at every stage of the progression all the parts must have been so cordinated into a harmonious whole1 that the animal could thrive and hold its own in the stress of competition4 ,could we but discover all the facts of environment1 on the one hand1 and organization1 on the other1 we should doubtless learn that the little ,eohippus was as exquisitely fitted to its place in the ,wasatch world1 as are the horses1 asses and zebras of the present day to theirs4 ,it was the response to changing needs1 whether of food1 climate1 disease or competition1 that was the main factor of development4 ,illustration3 ,,fig4 #aei4--,skeleton of a ,pampean horse 7,hippidion neogum74 ,national ,museum1 ,buenos ,aires4 ,for restoration1 see ,fig4 #aai1 p4 #bad4 ,note the splint-like nasal bones attached only at the hinder end4 #b4 ,titanotheriid4 ,titanotheres ,this family1 all of whose members vanished from the earth ages ago1 was a comparatively short-lived group and nearly the whole of its recorded history was enacted in ,north ,america2 only a few belated stragglers reached the eastern hemisphere1 though the family may1 nevertheless1 have originated there4 ,illustration3 ,,fig4 #afj4--,white ,river titanothere 7,titanotherium robustum7 males fighting4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,in the lowest of the three substages of the ,white ,river ,oligocene the most conspicuous and abundant fossils are the titanotheres1 the latest members of which were huge animals of almost elephantine proportions4 ,they belonged to four parallel1 or rather slightly divergent1 phyla1 differing in the development of the horns1 in the shape of the head and in the relative length and massiveness of the limbs4 ,the teeth were all low-crowned1 or brachyodont1 the canines much too small to have been of any service as weapons and the incisors had curious little1 button-shaped crowns1 which can have had little or no functional importance1 since they show hardly any wear1 even in old animals4 ,with such front teeth1 a prehensile lip and long tongue would seem to have been necessary for gathering and taking in food4 ,illustration3 ,,fig4 #afa4--,second upper molar1 left side1 of ,titanotherium4 ,a41 masticating surface2 ,b41 outer side of crown4 ,the titanotheres were one of two perissodactyl families in which the premolars never became so large and complex as the molars4 ,the upper molars had a longitudinal outer wall1 composed of two deeply concave cusps1 and two internal conical cusps1 but no transverse ridges2 the lower molars were composed of two crescents1 one behind the other1 a pattern which was very widely distributed among the early and primitive artiodactyls and perissodactyls4 ,the so-called 8horns0 were not strictly such1 but a pair of bony protuberances from the front of the skull and1 from their shape1 could hardly have been sheathed in horn4 ,the long1 immensely broad and massive head resembled that of some fantastic rhinoceros1 as did also the body and limbs4 ,the brain was quite absurdly small1 the cavity for it1 lost in the huge skull1 would hardly contain the fist of an ordinary man2 these great beasts must have been incredibly dull and stupid1 surpassing even the modern rhinoceroses in this respect4 ,as is generally true in mammals which have horns1 antlers1 or similar weapons borne upon the skull1 or very large tusks1 the bones of the brain-case were made enormously thick and yet lightened by an intricate system of communicating cavities or 8sinuses10 separated by many bony braces and supports connecting the inner and outer denser layers1 which form the surfaces of the bones4 ,in this way the skull is made strong enough without any proportionate increase of weight to endure the severe shock of impact1 when the horns or tusks are made use of4 ,the principle is the same as the engineer employs in designing a steel truss-bridge4 ,the upper profile of the head was deeply concave1 just as it is in those rhinoceroses which are armed with nasal horns4 ,illustration3 ,,fig4 #afb4--,skull of ,titanotherium elatum4 ,american ,museum4 ,the neck was of moderate length and the body1 as indicated by the long1 arched ribs and the greatly expanded hip-bones1 was extremely bulky and massive4 ,the spines of the anterior dorsal vertebr were excessively long1 forming a great hump at the withers4 ,the limbs and feet were columnar1 like those of an elephant2 the feet were supported on a great pad1 while the hoofs were mere excrescences on the periphery of the foot4 ,the bones of the fore-arm were entirely separate and the ulna was very stout2 in the lower leg also the bones were not cossified1 but the fibula was but moderately heavy4 ,this is a sharp contrast to the arrangement found in the horses and in those hoofed animals generally which are swift runners and have slender1 elongate limbs and feet1 such as deer1 antelopes1 camels1 etc4 ,heavy1 slow-moving animals1 like elephants1 tapirs1 rhinoceroses1 etc41 almost always have separate fore-arm and leg-bones and generally a heavy ulna4 ,the number of digits was four in the front foot and three in the hind4 ,the genera differed in the proportions of limbs and feet1 one having them longer and less ponderous than another1 and1 no doubt1 the former was of swifter gait4 ,at a certain level in the ,white ,river beds the titanotheres abruptly cease1 disappearing with what seems like startling suddenness4 ,in all probability1 however1 the extinction was more gradual and its apparent abruptness was due1 partly at least1 to the break in the deposition of the beds1 which is very obvious4 ,such a break1 or 8unconformity10 as geologists call it1 almost always implies an unrecorded lapse of time1 which may have been very long4 ,however it came about1 gradually or suddenly1 the extinction of these great animals is difficult to explain2 no ,carnivora of the time could have been formidable enemies and they had no rivals in their own walk of life4 ,their stupidity may have been a factor1 but it seems more likely that the onset of some new infectious disease1 perhaps imported by incoming migrants from the eastern hemisphere1 gave the coup de grace4 ,in the lower substage1 beneath the unconformity1 where the remains of titanotheres are so abundant1 successive changes may be observed4 ,the species with great 8horns10 rounded1 flattened or triangular1 are confined to the upper levels2 in the middle section other species1 somewhat smaller and with shorter 8horns10 are found1 while in the bottom levels the animals are much smaller and have still smaller 8horns40 ,the ,uinta titanotheres were much more numerous and varied than those of the ,white ,river2 in the upper part of these beds are found two genera 7,diplacodon and ,protitanotherium7 which already had quite prominent bony protuberances on the nose2 their canines were large enough to be of value as weapons and the incisors were well developed and functional4 ,evidently1 there was a change here in the manner of feeding1 the front teeth were used for cropping and browsing1 a function which in the ,white ,river members of the family must have been largely taken over by the lips and tongue1 while the growth of the horn-like protuberances on the skull rendered the canines superfluous as weapons4 ,this latter change is one which recurs frequently in different phyla of the hoofed animals1 in which the earlier and more primitive members had canine tusks1 and the later1 more advanced representatives developed horns1 the tusks diminishing as the horns increased4 ,while this rule is a general one1 it is not entirely without exceptions4 ,in the lower ,uinta and in the ,bridger the titanotheres were extremely abundant and numerically they are the commonest of all fossils in those beds2 no less than five series or phyla may be distinguished1 three of them being added in the upper ,bridger4 ,the differences between the phyla1 however1 principally concern the forms of the teeth and the shape of the skull2 in some the head was short and broad1 in others long and narrow1 and in others again of medium proportions2 some had broad and extremely low-crowned grinding teeth1 which in others were higher and more erect4 ,but these are matters of minor detail1 useful as they are in pointing the way to a proper arrangement of the various species2 in essentials1 the forms all agreed and constituted several series of closely allied genera4 ,comparing these ,bridger animals with the great titanotheres of the lower ,white ,river1 the first and most obvious difference that strikes the observer is the very much smaller size of the more ancient types4 ,with some variation in this respect1 hardly any of the ,bridger species exceeded a modern tapir in stature and very much resembled one in proportions4 ,the canine teeth were tusks as large as those of a bear and must have been very effective weapons2 the molar-pattern was identical with that found in the great ,oligocene beasts1 but the premolars were simpler and relatively smaller4 ,illustration3 ,,fig4 #afc4--,titanothere 7,mesatirhinus superior7 with long1 narrow head2 ,bridger stage4 ,restored from a skeleton in the ,american ,museum4 ,illustration3 ,,fig4 #afd4--,second upper molar1 right side of a ,bridger titanothere 7,palosyops74 ,the skull had a straight upper profile1 though in several of the phyla small bony protuberances were developed over the eyes1 and must clearly be regarded as incipient stages of the 8horns0 which were subsequently to become so long and prominent4 ,instead of being broad on top as it was in the ,white ,river genera1 the cranium carried a high ridge of bone1 the sagittal crest1 which served for the attachment on each side of the great temporal muscle1 one of the most important of the muscles of mastication4 ,the trunk was less massive and the limbs were lighter than in the ,oligocene genera1 but the number of digits was the same1 four in the front foot and three in the hind1 and the hoofs were much better developed1 serving actually to carry the weight and not being mere excrescences upon the periphery of a pad4 ,aside from the proboscis1 which lends such a characteristic appearance to the existing tapirs1 the titanotheres of the ,bridger must have looked much like tapirs1 and in early days1 when the mutual relationships had not been satisfactorily determined1 they were frequently described as 8tapiroid40 ,the term is unobjectionable in so far as it is understood that a merely superficial likeness is implied1 not any real relationship other than that which unites all the perissodactyl families4 ,as noted above1 the phyla of the titanotheres were much more numerous in the later than in the earlier part of the ,bridger stage1 when they were reduced to two4 ,in the still older ,wind ,river stage these two united into one4 ,the ,wind ,river animals 7,eotitanops7 were similar1 but much smaller1 and occurred in incomparably less variety and abundance4 ,indeed1 one of the most striking differences between the ,wind ,river and the ,bridger faunas consists in the great increase and diversification of the titanotheres in the latter4 ,there was1 it is true1 a second phylum of the family in the ,wind ,river1 represented by the genus ,lambdotherium1 but this was a short-lived series1 which left no descendants in the ,bridger or subsequent formations4 ,these were the smallest known members of the family and were light1 slender-limbed animals1 a very notable difference from the others4 ,with the ,wind ,river the history of the titanotheres breaks off short1 and from present information1 can be carried no farther back4 ,possibly1 there was a ,wasatch ancestor1 which only awaits discovery1 but it seems more likely that these earliest known genera were belated immigrants from the same as yet unknown region1 whence came the modernized and progressive elements of the ,wasatch fauna4 ,except for its obscure beginning1 the family was pre-eminently characteristic of ,north ,america1 and only two representatives of it have been found outside of that continent1 one in ,hungary and one in ,bulgaria4 ,no doubt others will yet be found in ,asia4 ,both in its resemblances and its differences1 as compared with the far longer and more complex story of the horses1 the history of the titanotheres has instructive bearings upon evolutionary theory4 7#a7 ,starting with two phyla1 one of which speedily died out1 the other ramified into four or five1 which continued until the disastrous end1 pursuing a nearly parallel course of development4 7#b7 ,there was a great increase in size and especially in bulk and massiveness from species no bigger than a sheep in the ,wind ,river stage to those which rivalled small elephants in the lower ,white ,river4 7#c7 ,the teeth underwent comparatively little change2 the incisors dwindled and lost functional importance and the canines were reduced1 horn-like growths taking their place as weapons2 the premolars grew larger and more complicated1 but never attained the full size and complexity of the molars1 as they did in other perissodactyl families4 7#d7 ,horn-like1 bony protuberances appeared first as small humps and knobs over the eyes and steadily enlarged1 at the same time shifting their position forward1 until they finally attained great size and were on the nose4 7#e7 ,the skull was modified so as to support these weapons and endure the shock of impact when they were put to use1 7a7 by making the upper profile strongly concave from before backward2 7b7 by greatly widening the top of the cranium1 where in the older and more primitive genera the high and thin sagittal crest was placed2 7c7 by immensely increasing the thickness of the cranial bones and at the same time hollowing them by means of an intricate system of cavities2 in this way sufficient strength was secured without undue increase in weight4 ,illustration3 ,,fig4 #afe4--,series of heads of titanotheres in ascending geological order4 ,a41 ,palosyops1 lower ,bridger4 ,b41 ,manteoceras1 upper ,bridger4 ,c41 ,diplacodon1 ,uinta4 ,d41 ,titanotherium1 extreme development of horns1 ,white ,river4 ,from models in the ,american ,museum and ,princeton ,university4 7#f7 ,the growth of the brain did not keep pace with the increase in the size and weight of the body and head1 and this deficiency may have been a factor in determining the early extinction of the family4 7#g7 ,to support the huge head1 stout ligaments and powerful muscles were needed in the neck and trunk and these in turn required large bony1 surfaces for their attachment4 ,to meet this need1 the spines of the anterior trunk-vertebr were very much lengthened1 so as to form a hump at the shoulders1 and this elongation of the spines went on in proportion to the growing weight of the head4 7#h7 ,the limb-bones increased in thickness until they became extremely massive1 to carry the immense weight of the body1 and they eventually lost the marrow-cavities1 which were filled up with spongy bone1 a great gain in strength4 ,as is generally1 though not universally1 true of the large and heavy mammals1 there was no cossification between the limb-bones and no great increase in their proportionate length4 ,the thigh-bone1 or femur1 lost the cylindrical shape of the shaft1 becoming flattened and very broad1 and acquiring something of the appearance of the same bone in the elephants4 ,illustration3 ,,fig4 #aff4--,right manus of titanotheres4 ,a41 ,titanotherium1 ,white ,river 7after ,marsh74 ,b41 ,palosyops1 ,bridger1 ,princeton ,university ,museum4 7#i7 ,there was no loss or cossification of elements in wrist 7carpus7 or ankle 7tarsus7 and no reduction of digits within the limits of the family4 ,in the latest1 largest and most specialized genera1 as well as in the earliest1 smallest and most primitive1 there were four toes in the front foot and three in the hind4 ,we have the most cogent reasons for assuming that all mammals were derived from ancestors which had five toes in each foot1 neither more nor less4 ,if this be true1 then the most ancient known titanotheres1 which were small and light1 had already suffered the loss of the first digit in the fore foot and of the first and fifth digits in the hind foot1 but there reduction ceased4 ,with the growing body-weight1 long1 narrow and slender feet would have been a detriment1 whereas in swift-running animals1 like horses and deer1 long and very slender feet are a great advantage4 ,the contrast is both striking and instructive1 showing the importance of a short1 broad1 polydactyl and pillar-like foot to very large and heavy mammals1 all of which have feet of this character4 7#aj7 ,the hoofs1 as shown by the terminal bones 7ungual phalanges7 which formed their bony cores1 were reduced in size until they became mere nail-like excrescences around the border of the massive foot4 #c1 #d4 ,tapirid and ,lophiodontid4 ,tapirs and ,lophiodonts ,the history of the tapir family is not at all satisfactorily known1 partly because tapirs are comparatively rare as fossils in all of the ,tertiary formations1 and still more for the reason that the specimens so far collected are so fragmentary1 not a single half-complete skeleton among them4 ,had these animals actually been as rare in ,north ,america as the fossils would seem to indicate1 they could not possibly have maintained themselves for so long a time1 throughout nearly the whole of the ,tertiary and ,quaternary periods4 ,for some reason1 probably because they have always been forest-haunting animals1 their habits must have kept them in places remote from the areas where the accumulation of sediments was in progress1 and thus only occasional stragglers were buried and preserved4 ,the rarity and incompleteness of the material render it impossible to give any such full account of the tapirs as is practicable for the horses and titanotheres1 but the circumstance is less unfortunate in the case of the tapirs than in that of many other families4 ,this is because these creatures have been so conservative and unprogressive1 that they have undergone comparatively little change since their earliest recorded appearance4 ,they have been aptly termed 8living fossils0 and seem like belated survivors from some older world1 out of place in the modern order of things4 ,attention has already been directed 7p4 #acg7 to the remarkable geographical distribution of the tapirs at the present time2 ,central and ,south ,america1 southeastern ,asia and the adjoining islands4 ,illustration3 ,,fig4 #afg4--;,american ,tapir 7,tapirus terrestris74 ,by permission of ,w4 ,s4 ,berridge1 ,london4 ,the tapirs are all of moderate size1 going back to very small forms at the beginning of their history and never at any period developing into large animals4 ,the only striking and unusual feature about any of the existing members of the family is the long proboscis1 a flexible1 dependent snout1 and1 were they all extinct and nothing known of them but the skull1 this proboscis could have been confidently predicated of them from the great shortening of the nasal bones4 ,small tusks1 not showing when the mouth is closed1 are formed in an exceptional way by the enlarged external upper incisor and the lower canine1 the upper canine being much reduced and without function4 ,the grinding teeth have very low crowns1 premolars 7except the first7 and molars are all alike and of a very simple pattern1 which has been independently repeated in several different orders of herbivorous mammals2 in both upper and lower teeth1 there are two elevated1 straight1 transverse crests4 ,illustration3 ,,fig4 #afh4--,skull of ,american ,tapir1 right side4 ,except for the modification of the skull which is conditioned by the development of the proboscis1 the skeleton might belong to any one of several ,eocene or ,oligocene families1 and it is this generalized1 indifferent character which has led to the dubbing of many early perissodactyls as 8tapiroids40 ,the limbs are short and moderately heavy1 the bones of the fore-arm and lower leg all separate and the number of toes is four in the front foot and three in the hind4 ,the toes end in well-formed separate hoofs1 but behind them is a pad1 which carries most of the weight4 ,the body is covered with smooth1 short hair1 which in the ,american species is of a uniform dark brown1 but in the ,asiatic species the head1 neck and limbs are black and the body is white4 ,in both1 however1 the young have longitudinal1 light-coloured stripes and spots on a dark ground 7see ,fig4 #f1 p4 #dg7 indicating what the colour-pattern of the ancestral forms must have been4 ,as might be inferred with certainty from the low-crowned teeth1 the tapirs are browsing1 not grazing1 animals1 feeding upon leaves and shoots and other soft vegetable tissues4 ,they are shy and solitary in habit and live usually in thick forests and near water1 which they frequently enter1 both for bathing and as a place of refuge when pursued4 ,under modern conditions1 the only perissodactyls of the western hemisphere are the tapirs of the ,neotropical region1 ,north ,america proper1 which for ages was the principal home of the order1 not having a single representative now4 ,in the ,pleistocene1 tapirs were apparently more abundant than in any of the ,tertiary epochs1 but this was probably due to the fact that the ,pleistocene of the forested regions is far more fully recorded than is any ,tertiary stage4 ,one species1 which was hardly distinguishable from the ,recent ,central ,american form1 was common in the forested region east of the ,mississippi and in ,california1 and a second species 7,tapirus haysii7 was larger and heavier than the other4 ,except in ,texas1 none have been found in the ,great ,plains area1 nor are they likely to be1 for that region1 then as now1 appears to have been devoid of forests4 ,no doubt1 these ,pleistocene species had substantially the same habits as the existing ones1 but they were adapted to a colder climate and a different vegetation1 for1 except the ,pinchaque ,tapir 7,t4 roulini7 of the high ,andes1 all the modern species are tropical in distribution4 ,concerning the ,pliocene and ,miocene tapirs1 but meagre information has been obtained4 ,enough material has been gathered by the collectors to demonstrate the continuous presence of the family in ,north ,america throughout those epochs1 but the broken and fragmentary specimens are insufficient to show what the structural changes were4 ,it should be remembered1 however1 that it is only in the region of the ,great ,plains and the ,great ,basin of ,nevada that any considerable quantity of ,miocene and ,pliocene mammals have been found1 and in those regions tapirs probably never were common4 ,if the ,peace ,creek formation of ,florida is properly classified as latest ,pliocene1 then at that time the ,american tapirs were essentially what they are to-day1 for the ,florida species is hardly separable from the modern ,t4 terrestris4 ,not till we reach the lower ,oligocene1 or ,white ,river beds1 do we get material which permits the making of definite statements regarding the course of developmental changes4 ,the ,white ,river genus1 ,protapirus1 which is also found in the middle ,oligocene of ,europe1 was a much smaller animal than any of the known ,pleistocene or ,recent species1 barely more than half the size1 in fact4 ,the teeth show that the small tusks were canines1 both above and below1 and that the curious substitution of the external upper incisor for the canine had not yet taken place4 ,the grinding teeth were identical in pattern with those of the existing genus1 but not all the premolars had yet acquired the form and size of the molars4 ,in the skull the nasal bones had begun to shorten1 but the change had not yet made much progress1 and the proboscis must have been in merely an incipient stage of development4 ,what little is known of the skeleton other than the skull was like that of the modern genus1 but the bones were much smaller and proportionately lighter4 ,illustration3 ,,fig4 #afi4--,skull of ,white ,river tapir 7,protapirus validus71 left side4 ,princeton ,university ,museum4 ,n4,b4 ,this figure is much less reduced than ,fig4 #afh4 ,the ,eocene tapirs are still very imperfectly known2 all that can be said of them is that they become successively smaller as they are traced backward in time1 and that in them the premolar teeth were all smaller and simpler than the molars4 ,the ,wasatch genus 7,systemodon7 is the most ancient member of the series yet discovered4 ,dating from the ,eocene immigration1 the tapirs are to be regarded as a ,north ,american family1 for there is here a complete continuity from the lower ,eocene to the ,pleistocene1 while in ,europe they first appeared1 probably by migration from ,north ,america1 in the middle ,oligocene4 ,illustration3 ,,fig4 #agj4--;,head of the ,white ,river tapir 7,protapirus validus74 ,restored from a skull in the museum of ,princeton ,university4 ,in ,south ,america the history of the tapirs is even shorter and less eventful than that of the horses2 the latter1 as we have seen1 reached the southern continent in the ,pliocene and there gave rise to a number of peculiar and characteristic genera1 but the tapirs have been found only in the ,pleistocene of ,argentina and ,brazil and only the modern genus is represented4 ,wofully broken and incomplete as the developmental history of the tapirs still is1 the fragments are nevertheless sufficient to show a mode of evolution differing in certain important respects from that followed by the horses or titanotheres4 ,certain features are common to all three groups1 such as the increase in size and in proportionate stoutness from stage to stage and the gradual enlargement and complication of the premolar teeth4 ,on the other hand1 the tapirs have been very conservative1 and they underwent far less radical changes than did either of the other families4 ,aside from the proboscis and the modifications of the skull which the development of that organ necessitated1 these animals remain to-day very nearly what they were in ,oligocene times4 ,this1 then1 is an example of development practically restricted to a few organs1 while all the other parts of the structure changed but little4 ,illustration3 ,,fig4 #aga4--,upper teeth1 left side1 of tapirs1 showing comparative sizes4 ,a1 ,protapirus validus1 ,white ,river ,oligocene4 ,b1 ,tapirus terrestris1 modern4 i#c1 external incisor4 c1 canine4 m#a1 first molar4 ,the extinct lophiodonts1 like the tapirs1 of which they would seem to have been near relatives1 are known only from incomplete material1 and comparatively little has been learned regarding their history4 ,while they were abundant and varied in ,europe1 during the ,eocene epoch1 they never were a striking or prominent element among the mammals of ,north ,america1 where they persisted one stage later1 and they did not reach ,south ,america4 ,in ,north ,america they are found from the ,wasatch to the ,white ,river4 ,the ,white ,river genus 7,colodon71 which is fairly well known1 might almost be described as combining the characters of horses and tapirs2 but such an expression is not to be interpreted as meaning that this genus is in any sense a connecting link or transition between the two families1 but merely that in certain important respects its course of development ran parallel with that followed by the horses4 ,the teeth were very tapir-like1 especially those of the lower jaw1 which1 indeed1 are hardly distinguishable from those of a tapir1 and the premolars had the molar-pattern4 ,the limbs were very light and slender and the feet long and narrow2 the fore foot retained a small fifth digit2 the feet1 especially the hinder one1 had a resemblance to those of the contemporary horses 7,mesohippus71 though the median digit was not so much enlarged1 nor the lateral ones so far reduced4 ,it is highly probable that1 had this family persisted till the ,pleistocene1 instead of dying out in the lower ,oligocene1 it would have eventually terminated in monodactyl forms4 ,the lophiodonts of the ,eocene are represented by very fragmentary material2 so far as that material goes1 it does not show much change from the ,white ,river genus1 except that the premolar teeth were smaller and simpler1 the limbs and feet retaining the same characteristics of length and slenderness4 ,the ,wasatch genus 7,heptodon7 had a similar lightness of limb and narrowness of feet1 these characters thus appearing at the very beginning of the family history1 so far as their ,north ,american career is concerned4 #e4 ,rhinocerotid4 ,true ,rhinoceroses ,the history of the great group of rhinoceroses and rhinoceros-like animals is a very long and complicated one1 inferior in its completeness only to that of the horses4 ,the complexity of the story arises from the large number of phyla into which the families are divisible1 and1 despite the great wealth of material and the admirable preservation of much of it1 it is extremely difficult to find a clew through the mazes of this labyrinthine genealogy4 ,from the standpoint of the existing geographical distribution of animals1 few mammals could seem more foreign and exotic to ,north ,american life than do the rhinoceroses1 and yet for a very long time that continent was one of the chief areas of their development1 so far1 at least1 as that development can be followed4 ,it is even probable1 though not clearly demonstrable1 that the family originated here and subsequently spread to the ,old ,world1 but not to ,south ,america1 where no member of it has ever been found4 ,the later history of the rhinoceroses ran its course in the ,old ,world entirely1 and the highest specializations within the family are to be found there2 in ,north ,america these animals are not known to have persisted beyond the lower ,pliocene1 and if they did survive1 it was only as a few stragglers in out of the way places4 ,the modern rhinoceroses are restricted to ,africa1 southern ,asia and some of the larger ,malay islands1 ,borneo1 ,sumatra and ,java1 and within these wide geographical limits are to be found the terminal representatives of at least three separate and quite distinct phyla1 the ,african1 ,indian and ,sumatran genera respectively 7,opsiceros1 ,rhinoceros1 ,dicerorhinus74 ,it will be advisable to begin the study of this peculiarly interesting family with a brief examination of its modern members1 even though none of these are found in the western hemisphere4 ,illustration3 ,,fig4 #agb4--,skull of the ,javan ,rhinoceros 7,r4 sondaicus74 ,note the single upper incisor1 and the rough surface on the nasal bones for the attachment of the single horn4 ,all the existing rhinoceroses are large and massive animals1 ranging from four feet to six feet six inches in height at the shoulder1 and all have solid dermal horns1 except in most females of the ,javan species#f 7,r4 sondaicus74 ,the ,indian and ,javan species have a single horn on the nose1 while those of ,africa and ,sumatra have1 in addition to the nasal horn1 a second one on the forehead4 ,the horns1 thus1 do not form a transverse pair1 but are placed in the median line of the head1 one behind the other2 it should also be noted that these horns are solid1 dermal structures1 made up of agglutinated fibres or hairs and not having a bony core formed by outgrowths of the skull1 as do the horns of most ruminants1 such as oxen1 sheep and antelopes1 which are therefore called 8hollow-horned0 7,cavicornia74 ,the skull1 however1 betrays the presence of horns by the extremely rough areas which serve for their attachment and thus the presence or absence of these weapons may be readily determined in the case of an extinct species of which only the skeleton remains4 ,the skin is very thick and coarse1 typically 8pachydermatous10 and is quite naked in most of the species2 but in the ,sumatran form there is a sparse coat of hair1 which is quite thick in the young animal4 ,in the ,indian ,rhinoceros unicornis the enormously thick skin has conspicuous and regularly arranged folds1 which make the creature look as though encased in armour2 the ears and tail are tufted with hair4 ,in the ,african and ,sumatran genera the folds are obscurely marked and not definitely arranged1 giving the body a smoother appearance4 ,all the existing species1 except one1 are browsers and feed upon leaves and twigs1 and they frequent forests and marshes where their food is abundant4 ,not that these and other browsing animals do not occasionally eat grass1 but it is not their principal diet4 ,the exception noted is the largest of all the living species1 the ,broad-,lipped ,rhinoceros 7erroneously called 8,white07 of ,africa1 ,opsiceros simus1 which is strictly a grazing animal and therefore frequents more open country than the other ,african species1 ,o4 bicornis4 ,there are considerable differences in proportions and general appearance among the various species1 but they all have short necks1 very long and massive bodies1 short and heavy limbs and short1 columnar feet1 which look much like those of elephants1 but have only three toes each4 ,in all but two of the living species the upper lip is prehensile and characteristically pointed and can be used to pick up very small objects1 like the 8finger0 on an elephant's trunk2 in the ,sumatran species 7,dicerorhinus sumatrensis7 the lip1 though pointed1 is horny and inflexible1 while in the ,african ,o4 simus it is broad and straight-edged4 ,the teeth of the modern rhinoceroses are extremely characteristic and may always be recognized at a glance4 ,in the ,african genus 7,opsiceros7 there are no front teeth1 all the incisors and canines being lost2 the other genera have on each side a single large and trenchant upper incisor1 in shape like a broad1 obliquely edged chisel1 which shears against a still larger elongate and tusk-like lower incisor1 that is procumbent and points directly forward4 ,the ,indian ,rhinoceros 7,r4 unicornis7 is said to use its tusks as weapons in very much the same fashion as the ,wild ,boar4 ,between the large lower tusks there is a pair of very small incisors1 which can have little or no functional value2 the third lower incisor has been suppressed1 as have also the canines of both jaws4 ,the dental formula then is3 i #a_/b or #j_/j1 c #j_/j1 p #d_/d1 m #c_/c1 #b #bh or #cd 7see p4 #ic74 ,the premolars1 except the first1 though somewhat smaller than the molars1 have essentially the same pattern4 ,the upper molars have moderately high crowns1 yet they are purely brachyodont1 except in the grazing1 broad-lipped ,african species 7,o4 simus71 in which they may fairly be called hypsodont4 ,the external wall of the tooth is broad and nearly smooth1 not divided into cusps1 as it is in the horses and tapirs1 and the two transverse crests1 which in the tapirs are directly transverse1 are very oblique4 ,in all the existing species additional complications are given by the short spurs1 which project inward from the outer wall or from the transverse crests4 ,the lower molars are formed each of two crescents1 one behind the other1 but their arms or horns are angulate1 not curved as they are in other perissodactyls which have crescentic lower teeth4 ,the upper surface of the skull is very concave in the antero-posterior direction and very broad over the cranium1 where there is no sagittal crest4 ,the nasal bones are immensely thick and strongly arched1 with the convexity upward2 both this arching of the nasals and the fore-and-aft concavity of the skull are devices for giving a strong and solid attachment to the great nasal horn1 for the attachment of which these bones have an extremely rough surface1 and in the two-horned species1 a second roughened area on the forehead marks the place of attachment of the frontal horn4 ,the bones of the cranium are very thick1 but lightened by the many chambers which traverse them4 ,the articulation of the lower jaw with the skull is in some respects unique among mammals2 the postglenoid process is a long spike1 which fits inside of a bony lump 7the postcotyloid process7 behind the condyle of the lower jaw1 and the posterior margin of the latter is greatly thickened4 ,the neck is short and stout1 the trunk very long1 broad and deep1 the long and strongly arched ribs and the widely expanded hip-bones providing space for the great mass of viscera4 ,the bones of the limbs are short and very massive2 the humerus has a very prominent deltoid ridge and the femur an unusually large third trochanter2 the bones of the fore-arm and lower leg are separate1 as in the massive ungulates generally4 ,the foot-bones are likewise extremely short and heavy1 and the number of digits is three in each foot4 ,each of the five or more existing species has its skeletal peculiarities1 every portion of the bony structure showing characteristic features2 but these are only minor modifications of the general plan and may be neglected in any comprehensive account of the living representatives of the family4 ,illustration3 ,,fig4 #agc4--,left manus of ,indian ,rhinoceros 7,r4 unicornis74 ,in order to find any ,american members of this family1 it is necessary to go back to the lower ,pliocene1 where a great abundance of them is encountered1 representing1 according to ,osborn's view1 four or five phyla2 and just as in the case of the horses of the same formation1 they were an assemblage curiously made up of progressive and old-fashioned1 conservative genera1--some were persistent native stocks1 others the descendants of immigrants from the ,old ,world1 which reached ,america in the middle ,miocene4 ,there was great variety of form1 size and proportions among these animals1 ,north ,america at that time having a larger number of genera and species than ,africa and ,asia combined have now4 ,some were quite small1 some large1 though none equalled the larger modern species4 ,some of the genera had relatively long legs1 but in one genus1 ,teleoceras 7,fig4 #abe1 p4 #bcj71 an ,old ,world type1 they were most grotesquely short1 the belly almost touching the ground1 as in a hippopotamus4 ,most of these rhinoceroses were hornless1 but ,teleoceras had a small horn on the very tip of the nose4 ,in consequence of the lack of horns1 the nasal bones were thin and weak1 in marked contrast to the massive1 convex nasals of the modern species1 and1 for the same reason1 the upper profile of the skull was nearly straight4 ,except for minor details1 the dentition was in very nearly the modern stage of development2 there was a single trenchant upper incisor on each side1 a procumbent lower tusk and between the tusks a pair of small incisors2 the other incisors and the canines were already lost4 ,one genus 7,peraceras7 had lost all the upper front teeth4 ,the grinding teeth had the same character as in the existing species1 but were somewhat simpler1 owing to less development of the accessory spurs4 ,in the more progressive types the teeth were rather high-crowned1 though in none were they actually hypsodont2 while the persistent ancient genera had teeth with much lower crowns4 ,aside from the differences in the skull1 which are obviously to be correlated with the absence or very small size of the horn1 the skeleton in these ,pliocene genera differed but little from the type common to the existing rhinoceroses1 and in all the species the feet were three-toed4 ,in short1 the dentition and skeleton1 except the skull1 had already attained to substantially the modern conditions4 ,while the ,old ,world at that time had both horned and hornless rhinoceroses in abundance1 none of the genera with large and fully developed horns ever migrated to the western hemisphere4 ,this is the more remarkable in that the great ,woolly ,rhinoceros 7,opsiceros antiquitatis7 of the ,pleistocene1 which had two very large horns1 inhabited ,siberia with the ,mammoth 7,elephas primigenius74 ,the latter extended its range through ,alaska and the northern ,united ,states1 but the rhinoceros1 for some unknown reason1 did not accompany it in its eastward wanderings4 ,the rhinoceroses of the upper ,miocene did not differ sufficiently from those of the lower ,pliocene to call for particular attention4 ,needless to say1 there were differences between the species of the two epochs1 but in such a sketch as this only the broader and more obvious changes can be taken into account4 ,even in the middle ,miocene the only feature which calls for notice was the first appearance in ,north ,america of the ,old ,world genus ,teleoceras1 which became so abundant in the upper ,miocene and lower ,pliocene4 ,the middle ,miocene species 7,t4 medicornutus7 would seem to have been descended from ,t4 aurelianensis of the lower ,miocene of ,france2 the two species agreed not only in having a small horn on the tip of the nose1 but also in the presence of a still smaller one on the forehead4 ,in the lower ,miocene but two phyla of rhinoceroses have been found1 both of which were the comparatively little changed descendants of ,oligocene ancestors2 and there was thus a notable difference from the rhinoceroses of the middle ,miocene and subsequent stages1 which were decidedly more modern in character4 ,one of these phyla was constituted by those rhinoceroses 7,diceratherium1 ,fig4 #abi1 p4 #bci7 which had a transversely placed pair of horns on the nose1 not one behind the other1 as in all of the subsequent two-horned species1 of which ,north ,america had but the one middle ,miocene form 7,t4 medicornutus7 mentioned above4 ,the lower ,miocene species of ,diceratherium was a very small animal1 and smaller than any member of the family from later formations4 ,the diceratheres originated in ,north ,america1 and the stages of their development may be clearly made out2 they also migrated to the eastern hemisphere and have been found in ,france1 though it is possible that the genus was not truly monophyletic and arose independently in both hemispheres4 ,the second phylum is that of the hornless forms 7,cnopus7 which were so abundantly represented in the ,oligocene and persisted with little change into the ,pliocene4 ,in the upper ,oligocene1 or ,john ,day1 the diceratheres are the only rhinoceroses certainly yet obtained1 and of these there were several species1 large and small4 ,the hornless forms may have been present in ,oregon1 but this has not been clearly demonstrated4 ,that they continued to exist somewhere during that stage is hardly open to question1 for they reappeared in the lower ,miocene4 ,from the ,white ,river1 or lower ,oligocene1 many well-preserved rhinoceroses1 including complete skeletons1 have been gathered in the various collections and display very interesting differences in the three substages of the ,white ,river beds4 ,in the uppermost substage is found the apparent beginning of the dicerathere phylum1 though it may be traced back to the middle substage2 the nasal bones had become much thickened so as to serve as a support for the horns1 and these are indicated by a small1 but very rough1 area on the outer side of each nasal4 ,comparing this ,white ,river species with those of the upper ,oligocene and lower ,miocene1 two differences may be observed3 in the later species the horn-supports were well defined bony knobs or prominences1 and these knobs were close to the anterior ends of the nasals2 while in the ,white ,river animal the places for the attachment of the horns were mere roughened areas1 and these were well behind the tips of the nasals4 ,this is not an infrequent sort of change1 that horns should shift their position forward or that the portion of the nasals in front of the horns should be shortened4 ,parallel changes occurred among the titanotheres4 ,in the middle ,white ,river all the rhinoceroses were hornless1 but the same two phyla may be distinguished2 the actual starting point of the diceratheres had no indication of the nasal horns1 but may be identified as such by their close resemblance in other respects to the species of the upper substage in which the incipient horns appeared4 ,much commoner were the members of the typical hornless line 7see ,fig4 #ace1 p4 #bef71 which1 though true and unmistakable rhinoceroses1 were yet far removed in many details of structure from the progressive genera of the middle and upper ,miocene4 ,there are several species in this phylum1 which constitute a series of diminishing size almost in proportion to their increasing antiquity4 ,the dentition was already thoroughly and characteristically rhinoceros-like1 but a more primitive feature was the presence of a second upper incisor1 a small tooth placed behind the trenchant one1 making the incisor formula #b_/b2 the third incisor and the canines of both jaws were already lost4 ,the assumption of the molar-pattern by the premolars varied much in degree of completeness in the different species2 the upper molars1 while having all the essentials of the rhinocerotic plan of structure1 had a much less complex appearance than in the ,recent genera1 because of the absence of the accessory spurs2 and all the grinding teeth were very low-crowned1 in strong contrast to the high-crowned 7yet not properly hypsodont7 teeth of the middle ,miocene and subsequent genera4 ,illustration3 ,,fig4 #agd4--,skull of hornless rhinoceros 7,cnopus tridactylus72 middle ,white ,river stage4 7,after ,osborn47 ,illustration3 ,,fig4 #age4--,second upper molar1 left side1 of ,cnopus1 showing the masticating surface4 ,as already mentioned1 there was much variation in size among the species1 but none was as large as those of the ,miocene and ,pliocene genera1 not to mention the enormous animals of the ,pleistocene and ,recent epochs in the ,old ,world4 ,the commoner species of the middle ,white ,river substage 7,cnopus occidentalis7 was an animal nearly equalling in size the ,american ,tapir 7,t4 terrestris7 and quite like that species in its proportions1 the limbs being relatively longer and less heavy and the feet narrower than in the rhinoceroses of the subsequent geological epochs4 ,the skull1 being hornless1 had thin1 pointed and nearly flat nasal bones1 an almost straight and horizontal upper profile1 and a short and low1 but distinct1 sagittal crest2 the cranial bones were quite thin1 there being no extensive development of sinuses within them4 ,the articulation of the lower jaw with the skull was only beginning to take on the characteristic peculiarities seen in the later genera1 and the hinder margin of the lower jaw was not much thickened4 ,thus1 many of the features which distinguish the skull in all ,recent and ,pleistocene and most ,pliocene1 and upper and middle ,miocene rhinoceroses were entirely lacking in ,cnopus1 yet no anatomist could doubt that the ,white ,river animal was a genuine rhinoceros4 ,the neck was short1 but not very heavy1 the trunk elongate1 but not massive1 the ribs not being inordinately long nor strongly arched1 and the hip-bones so little expanded that they were tapiroid rather than rhinocerotic in appearance4 ,the limb-bones were relatively much more slender than in any existing species1 and1 although every one of them was characteristically that of a rhinoceros1 yet the comparative lightness of body and slenderness of limb gave to these bones a certain resemblance to those of tapirs4 ,the feet1 which were moderately elongate and rather narrow1 were three-toed1 as in all subsequent ,north ,american species and in all existing members of the family4 ,the most ancient and primitive representative of the true rhinoceroses so far discovered occurs in the lowest division of the ,white ,river beds and is of particular interest as throwing light upon the origin of the family4 ,the genus 7,trigonias7 differed from that 7,cnopus7 which was so abundant in the middle ,white ,river substage in several highly significant particulars1 though on a merely casual inspection one might easily be misled into thinking that the two animals were nearly identical1 for ,trigonias was an undoubted rhinoceros4 ,such an identification1 however1 would be a great mistake1 for the differences1 though not striking1 are very important4 ,in the upper jaw the first or anterior incisor had already assumed the characteristic trenchant1 chisel-like shape1 but two other incisors were present also1 thus bringing the number up to the original three1 common to all early perissodactyls2 even more interesting is the presence of a small upper canine4 ,the lower jaw likewise had three incisors on each side1 the first and third small1 the second enlarged and tusk-like1 but the canine had already been suppressed1 and thus the dental formula was3 i #c_/c1 c #a_/j1 p #d_/d1 m #c_/c1 #b #db1 or #ad more than the formula of the existing ,african species4 ,the premolars were smaller and less complex than the molars4 ,illustration3 ,,fig4 #agf4--,skull of ,trigonias osborni1 lower ,white ,river4 7,after ,hatcher47 ,illustration3 ,,fig4 #agg4--;,anterior end of right upper jaw of ,trigonias osborni 7after ,lucas74 c41 canine4 i #c1 external incisor4 i #b1 middle incisor4 i #a1 first incisor4 ,from this ancient genus may readily be inferred the steps by which the peculiar characters of the anterior teeth in the true rhinoceroses were attained4 ,the first stage was undoubtedly an animal in which1 as in all other ,eocene perissodactyls1 there were three well-developed incisors on each side of both jaws1 #ab in all1 and moderately prominent canine tusks2 all these teeth were erect4 ,the second stage was the enlargement of the first upper and second lower incisors1 the latter becoming less erect and beginning to assume the recumbent position2 at the same time the other incisors and the canines were reduced in size and were so little used that they lost their functional importance4 ,the third stage1 in which the first and second lower incisors were horizontal and pointed directly forward1 and the first upper and second lower teeth were still further enlarged1 the non-functional teeth reduced in size and the lower canine suppressed1 was realized in the genus ,trigonias4 ,there were thus but two hypothetical stages between this lower ,white ,region genus and the tapir-like forms of the middle ,eocene1 so far1 at least1 as the anterior teeth are concerned4 ,illustration3 ,,fig4 #agh4--;,anterior end of left upper jaw of ,cnopus1 ,a1 adult2 ,b1 immature animal 7after ,osborn74 ,i #a1 first incisor2 ,i #b1 second incisor2 ,c1 canine4 ,the skeleton of ,trigonias was1 on the whole1 very much like that of the succeeding genus1 ,cnopus1 of the middle substage of the ,white ,river1 but with the important exception that the front foot had four digits instead of three4 ,the pollex1 or first of the original five1 almost always the first to disappear1 had been suppressed1 the third or median digit was already the largest of the series1 both in length and breadth2 the second and fourth1 somewhat shorter together made a symmetrical pair1 while the fifth1 though much the most slender of all1 was still functional and had retained all of its parts4 ,in the hind foot the digits had been reduced to three4 ,this arrangement1 four toes in the manus and three in the pes1 is the same as is found in the existing tapirs and in the ,eocene perissodactyls generally1 with only two or three known exceptions4 ,in the ,oligocene1 on the other hand1 all the genera except the titanotheres1 tapirs1 lophiodonts and amynodonts were tridactyl both before and behind4 ,illustration3 ,,fig4 #agi4--,left manus of ,trigonias osborni4 7,after ,hatcher47 ,with ,trigonias the definitely known history of the true rhinoceroses breaks off abruptly1 and it is possible that that genus was an immigrant1 though it is perhaps more likely that its ancestors existed in the upper and middle ,eocene 7,uinta and ,bridger stages7 of ,north ,america4 ,some fragmentary specimens from the ,uinta beds1 too imperfect for any definitive identification1 are an encouragement to hope that the forerunner and direct ancestor of ,trigonias may yet be discovered in that formation4 ,it is also quite possible that one of the larger species of the genus ,hyrachyus1 so abundant in the ,bridger and going back to the ,wind ,river1 may take its place in the same series4 #f4 ,hyracodontid4 ,cursorial and ,aquatic ,rhinoceroses ,the luxuriant diversification of the rhinoceros-stem was not exhausted by the many phyla of what we have called the true rhinoceroses4 ,two other series1 very distinctly marked and rather distantly connected with the first1 are yet to be considered4 ,these two series1 the hyracodonts 7in the narrow sense7 and the amynodonts1 ran courses which1 in certain respects1 were singularly alike2 both were of ,north ,american origin and one1 the hyracodonts1 was entirely confined to that continent1 while the other sent out late migrants1 which entered ,europe1 no doubt through ,asia1 and both ended their careers before the close of the ,white ,river time4 ,their history was thus a brief one when compared with that of the true rhinoceroses1 three phyla of which persist to the present day1 though their geographical range is greatly restricted in comparison with what it was in the ,miocene and ,pliocene1 when they ranged over every continent except ,australia and ,south ,america4 ,just how to classify these three series of rhinoceroses and rhinoceros-like animals1 so as most accurately to express their mutual relationships1 is a question that has received several answers4 ,one method suggested is to include them all in a single family and to make a subfamily for each of the three well-distinguished series2 this is the arrangement which personally ,i should prefer4 ,a second plan is to accord family rank to each of the three groups2 while the most elaborate scheme1 that of ,professor ,osborn1 is as follows3 for the rhinoceroses1 in the broader sense1 he makes two families1 the ,rhinocerotid and the ,hyracodontid1 and divides the former into four subfamilies1 which include all of the true rhinoceroses1 living and extinct1 of the ,old and ,new ,worlds1 and the latter into two subfamilies1 the ,hyracodontin and ,amynodontin4 ,it is not a matter of very great moment as to which of these three schemes is followed1 and ,i shall therefore adopt the one proposed by ,professor ,osborn1 in order to avoid1 so far as possible1 the confusing effect of different methods of classification4 ,illustration3 ,,fig4 #ahj4--;,cursorial rhinoceros 7,hyracodon nebrascensis71 ,white ,river stage4 ,restored from a skeleton in the ,museum of ,princeton ,university4 ,as before mentioned1 the subfamily of the hyracodonts 7,hyracodontin7 became extinct in ,white ,river times1 during most of which it was represented by the single genus ,hyracodon1 whence are derived the names for the family and subfamily4 ,the series was purely ,north ,american1 and no member of it has ever been found in any other continent4 ,the species of ,hyracodon were altogether different in appearance and proportions from the true rhinoceroses1 being lightly built1 slender1 cursorial creatures1 suggestive rather of horses than of rhinoceroses1 to which they bore much the same relation as the slender-limbed1 narrow-footed lophiodonts did to the tapirs 7see p4 #cbf72 in size1 they were somewhat taller and considerably heavier than a sheep4 ,the low-crowned grinding teeth had the unmistakable rhinoceros-pattern1 and between them and the teeth of the contemporary ,cnopus the difference was merely one of size1 except for one small1 but not insignificant feature4 ,the last upper molar had not perfectly acquired the triangular form characteristic of all the true rhinoceroses1 caused by the complete fusion of the outer wall with the posterior crest1 but the wall projected a little behind the crest1 as in perissodactyls generally4 ,premolars 7except the first7 and molars were alike in structure and of nearly the same size4 ,while the grinding teeth were thus hardly to be distinguished from those of the true rhinoceroses1 the anterior teeth1 incisors and canines1 were totally different2 they were very small and had simple1 pointed and slightly recurved crowns1 and were all very much alike in size and form4 ,thus1 there were in the front of the mouth eight small1 hook-like teeth1 above and below1 which were obviously quite useless as weapons2 and as the skull had no horn1 the animal was defenceless1 and must have depended entirely upon speed for its safety from the attacks of the larger and more powerful beasts of prey4 ,the skull was short1 deep and thick1 and the head must have been heavy and clumsy1 quite out of keeping with the body and limbs4 ,the neck was surprisingly long1 longer indeed proportionately than in the contemporary genus of horses 7,mesohippus71 but the neck-vertebr were relatively stout and strong1 as was required for the muscles to move and control the heavy head4 ,the body was rather elongate1 but not deep or massive1 and the limbs were proportionately much longer than in any of the known rhinoceroses4 ,the limb-bones1 one and all1 despite their length and slenderness1 bore an unquestionable likeness to those of the true rhinoceroses4 ,in this elongation of the limbs the fore-arm and thigh were the parts most affected1 and the slenderness1 though in notable contrast to the proportions both of the true rhinoceroses and the amynodonts1 was yet much less marked than in the middle ,eocene representatives of the hyracodonts themselves4 ,the feet were long and narrow1 approximating1 though not actually attaining the proportions of the feet in the ,white ,river horses 7,mesohippus74 ,there were three digits in each foot1 and the median toe 7third of the original five7 was so much enlarged and the lateral toes 7second and fourth7 so reduced1 though still functional1 as strongly to suggest a monodactyl foot as the outcome of this course of development1 had not the early extinction of the subfamily put an end to it4 ,it is interesting to reflect that1 had the lophiodonts and hyracodonts continued their existence to the present time and had persisted in advancing along their particular lines of specialization1 we should1 in all probability1 have had monodactyl tapirs and rhinoceroses1 as well as horses4 ,illustration3 ,,fig4 #aha4--,left manus of cursorial rhinoceroses4 ,a1 ,triplopus cubitalis 7after ,cope71 upper ,bridger4 ,b1 ,hyracodon nebrascensis1 ,white ,river4 ,as in the case of so many other mammalian series1 the hyracodonts of the but partially explored ,uinta formation are still very imperfectly known4 ,almost all that can be positively stated about them is that they were smaller than their ,white ,river successors and that the assumption of the molar-pattern by the premolars was incomplete4 ,in the upper ,bridger beds also not very much is known regarding the then representatives of the series1 7,triplopus74 ,so much is clear1 however1 that they were still smaller and lighter animals1 that the limbs were very light1 and that the number of digits in the fore foot had already been reduced to three1 the only known ,bridger perissodactyl of which this is true1 all the others having four digits in the manus and three in the pes4 ,illustration3 ,,fig4 #ahb4--,primitive cursorial rhinoceros 7,hyrachyus eximius71 lower ,bridger4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,in the middle and lower ,bridger1 and even in the ,wind ,river1 occurs a genus 7,hyrachyus7 which contained a large number of species1 ranging in size from a full-grown modern tapir to creatures no larger than foxes4 ,it is among these smaller species that the most ancient member of the hyracodont line is to be sought1 though it is not yet practicable to select any particular one4 ,hyrachyus1 indeed1 may very possibly have contained among its many species the ancestors of all three lines of the rhinoceroses and rhinoceros-like animals1 and thus formed the starting point from which they developed in diverging series4 ,it is always a very significant fact when two or more groups approach one another the more closely1 the farther back in time they are traced1 because that can only be interpreted to mean that ultimately they converged into a common term1 even though that common ancestor should elude discovery4 ,hyrachyus may be described as a generalized1 relatively undifferentiated perissodactyl1 from which almost any other family of the order1 except the horses and the titanotheres1 might have been derived4 ,the incisors1 present in undiminished number1 were well developed and functional1 but not large1 and the canines were moderately enlarged1 forming small tusks4 ,the premolars were all smaller and less complex than the molars1 which had a strong resemblance to those of the tapirs2 in the lower jaw they were identical with the latter1 but in the upper jaw there was more than a suggestion of likeness to the rhinoceroses4 ,the skull was long1 narrow and low1 hornless1 and with thin1 slender nasals and straight1 horizontal upper contour4 ,the neck was short1 the body very long and the limbs of medium length and weight2 though relatively stouter than in ,triplopus of the upper ,bridger and ,uinta beds1 they cannot be called heavy4 ,the feet were not especially elongate and rather slender2 the manus had four toes and the pes three4 ,illustration3 ,,fig4 #ahc4--,skull of ,hyrachyus4 7,after ,osborn47 ,a brief and short-lived branch of this stock existed in the ,bridger stage1 but was not1 so far as is known1 represented in any of the subsequent stages1 and was made up of a single genus 7,colonoceras7 which had a small pair of dermal horns upon the nasal bones4 ,in other respects1 it was like ,hyrachyus4 ,it is surprising to find that the horned series should have so speedily died out1 while the defenceless forms not only persisted1 but actually became more defenceless through the reduction of the canine tusks4 priori1 one would have expected the opposite result1 but the key to the enigma is probably to be found in the more perfect adaptation of the surviving kinds to swift running4 ,the second subdivision 7,amynodontin7 of this family contains a series of animals which developed in a very divergent fashion and went to quite the opposite extreme from the cursorial hyracodonts1 resembling the latter 7aside from the fundamental characteristics common to all rhinoceroses1 in the broadest sense of that term7 only in the pattern of the molar teeth and in the absence of horns4 ,the terminal member of the amynodont series was a ,white ,river genus 7,metamynodon7 of which the remains have been found almost exclusively in the consolidated and cemented sands filling the old river-channels of the middle substage of the ,white ,river beds4 ,this fact1 together with certain structural features of the skull and skeleton1 leads at once to the suggestion that these animals were chiefly aquatic in their habits and somewhat like hippopotamuses in mode of life4 ,metamynodon was quite a large animal1 the heaviest and most massive creature of its time1 after the disappearance of the giant titanotheres1 but was low and short-legged4 ,the true rhinoceroses1 save those which1 like the existing ,african species1 have lost all the front teeth1 all agree in the peculiar differentiation of the incisors1 which was fully described in the preceding section of this chapter4 ,the hyracodonts had a second scheme1 the incisors and canines being all similar in shape1 small1 pointed and recurved1 while still a third mode of development was exemplified by the amynodonts1 in which the canines became large and formidable tusks1 a very notable difference from all other rhinoceroses whatever4 ,illustration3 ,,fig4 #ahd4--,supposedly aquatic rhinoceros 7,metamynodon planifrons7 of the ,white ,river4 ,restored from a skeleton in the ,american ,museum4 ,in ,metamynodon the incisors were not enlarged1 but were unreduced and functional2 the upper canine was a short1 heavy tusk1 obliquely truncated by the abrasion of the lower tusk1 which was very large4 ,another striking difference from all the other groups of rhinoceroses was the reduction of the premolar teeth1 which1 instead of equalling the molars in size1 were much smaller and were diminished to three in the upper1 two in the lower jaw4 ,the molars were of the characteristic rhinoceros-pattern1 but were very narrow1 especially the inferior ones1 in which the enamel did not surround the whole crown1 as it normally does1 but was lacking along vertical bands1 where the dentine formed the surface4 ,the skull was extremely peculiar and1 with its very long and high sagittal crest and immensely expanded and heavy zygomatic arches1 had a surprising likeness to the skull of some great beast of prey4 ,the face was very much shortened and the skull depressed1 so that the head was remarkably low1 broad and flat1 proportions which did not recur in any other group of rhinoceroses4 ,the neck was short1 the body very long and very massive1 as is shown by the long and strongly arched ribs4 ,the limbs were short and stout and the feet quite primitive in character1 the front foot retaining four fully developed and functional digits4 ,no other perissodactyls of the middle ,white ,river beds1 except the lophiodonts and tapirs1 had more than three digits in the manus1 and thus ,metamyodon was a belated exception to the general rule4 ,the ,uinta member of this series was ,amynodon1 a similar but smaller and lighter animal4 ,the canine tusks were of more moderate size and none of the premolars had been lost1 but were considerably smaller than the molars1 and the last two had assumed the molar-pattern4 ,the face was not conspicuously shortened and the zygomatic arches of the skull were not so heavy or so widely expanded as in the ,white ,river genus1 and the skeleton was less massive4 ,the genus ,amynodon is also represented in the upper ,bridger beds1 but by a species different from that of the ,uinta stage4 ,this more ancient species was a smaller animal than its upper ,eocene successor and had less enlarged canine tusks1 but it already possessed the typical rhinoceros molar teeth1 the only ,bridger mammal of which this is true4 ,beyond this species the line1 as at present understood1 cannot be traced1 though probably some species of ,hyrachyus1 or an allied genus1 will prove to be the ancestor sought2 but the connecting link has not yet been brought to light4 ,the history of the rhinoceroses and rhinoceros-like animals1 of which a very much simplified sketch has just been given1 is a highly complex one1 much more so than that of the horses1 titanotheres1 or tapirs1 and is less fully recorded1 the earlier chapters of the story being still missing4 ,however1 in the progress of discovery these chapters will almost certainly be recovered1 and it is already possible to draw close inferences as to what they will reveal4 ,the complexity of the history is chiefly due to the fact that1 as compared with the other perissodactyl groups1 the rhinoceros stem ramified more widely and gave rise to more divergent and diversified forms4 ,at one extreme1 we find huge1 massive1 slow-moving types2 and1 at the other1 light1 slender1 cursorial creatures1 almost horse-like in appearance1 with intermediate forms of moderate size4 ,some were long and others short legged1 mostly adapted to terrestrial life1 but some with aquatic habits4 ,the three very different sorts of modification which the anterior teeth 7incisors and canines7 underwent in the three principal series may be taken as an illustration of this divergent development1 and to these may be added a fourth1 the complete suppression of all the incisors and canines above and below1 as is exemplified by the modern ,african species4 ,of the three rhinoceros groups1 whatever rank be assigned them1 family or subfamily1 much the most prolific in divergent forms was that of the true rhinoceroses 7,rhinocerotid7 of which seven or more phyla have been distinguished1 three of them surviving to the present time4 ,only in this series were horns frequently present1 the brief experiment1 as it might be called1 of the ,bridger genus ,colonoceras1 being the only known instances of horns among the hyracodonts1 and the amynodonts were all hornless4 ,in making the comparison as to degree of ramification among the three series1 it should be borne in mind that the true rhinoceroses were the only long-lived group1 the other two dying out before or at the end of the ,white ,river stage4 ,within the series or family of the true rhinoceroses1 there was no great divergence of type1 and all the members were much alike1 heavy and slow animals1 but with very great variety in the details of structure4 ,take1 for instance1 the matter of horns2 we find both hornless and horned genera1 the former preceding the latter in time1 but1 so far as ,north ,america is concerned1 continuing in association with them till the end4 ,among the horned genera1 the horn may be single1 double in a transverse pair 7,diceratherium7 or arranged one behind the other in the median line of the head 7,dicerorhinus1 ,opsiceros1 etc474 ,the single horn may be on the nose or the forehead2 if on the nose1 it may be on the upper side of the nasal bones 7,rhinoceros7 or on the extreme tip and pointing obliquely forward 7,teleoceras74 ,the single frontal horn was much less common1 but in the extraordinary ,elasmotherium1 of the ,european and ,siberian ,pleistocene1 the horn was of gigantic size and the surface for its attachment an enormous1 dome-like boss on the forehead4 ,all three of the series had their most ancient known representatives in ,north ,america1 and it seems probable1 though by no means certain1 that they all originated here by divergence from a common stock1 which was represented more or less closely by the genus ,hyrachyus of the ,bridger and ,wind ,river stages of the ,eocene4 ,however that may be1 true rhinoceroses flourished exceedingly in the ,old ,world from the upper ,oligocene to the ,pleistocene1 the events of the latter epoch restricting them to their present range4 ,the significance of the ,american genera for the ancestry of the modern types can be found only in the most ancient forms1 ,trigonias and ,cnopus2 the subsequent development which led up to the existing species of ,asia and ,africa went on entirely in the eastern hemisphere4 ,the hyracodont subfamily had no known representatives outside of ,north ,america1 but the amynodonts sent out emigrants1 which appeared for a brief time in the ,oligocene of ,europe4 ,in the varied history of the rhinoceroses1 the principles of evolutionary change which may be deduced from the recorded development of the horses1 tapirs and titanotheres are found to be applicable4 7#a7 ,there was the same gradual increase in size from the earlier to the later geological stages4 ,not that all the phyla kept equal pace in this respect1 and even within the same phylum it was the rule rather than the exception to find larger and smaller contemporary species4 7#b7 ,in all of the early forms1 up to the middle ,miocene1 the teeth were low-crowned2 after that time there was a decided increase in the height of the teeth1 though only in ,elasmotherium was the fully hypsodont1 cement-covered crown attained4 ,in the existing ,african ,broad-,lipped ,rhinoceros 7,opsiceros simus71 which is a grazing animal1 the high1 cement-covered teeth may also fairly be called hypsodont4 7#c7 ,in all of the lines1 as in the other perissodactyl families1 the premolars gradually took on the pattern of the molars2 only in the amynodonts were the premolars notably reduced in number and size4 7#d7 ,the three different modes of development of the anterior teeth1 exemplified by the true rhinoceroses1 the hyracodonts and amynodonts respectively1 need not be recapitulated here4 ,it is sufficient to call attention to the fact that the three kinds of modification diverged from a common starting-point such as may be seen in the middle ,eocene perissodactyls generally1 and that in each series the transformation was gradual4 7#e7 ,the modification of the skull followed several different courses1 as designated by the major and minor subdivisions of families1 subfamilies and phyla4 ,the development of horns1 whether single or double1 in transverse or longitudinal pairs1 was the most important single influence in transforming the skull1 as determined by the mechanical adjustment necessary to make these weapons effective1 but even in the hornless forms changes went on1 and in all the phyla the skull departed more and more widely from the primitive ,eocene type in each succeeding geological stage4 ,the most aberrant form of skull was that of the hornless and presumably aquatic ,metamynodon1 in which the greatly shortened face1 high sagittal crest and extremely wide zygomatic arches were altogether exceptional4 7#f7 ,when the history of any horned phylum is at all complete1 the development of the horns may be followed step by step from the marks which they left upon the skull4 ,as a rule1 the story was one of gradual enlargement1 but1 in one case at least1 an incipient horn apparently failed to enlarge and was eventually lost4 7#g7 ,in the light1 slender and cursorial hyracodonts the mode of development resembled that of the horses1 as appears in the elongation of the neck1 limbs and feet1 in the enlargement of the median toe and concomitant reduction of the lateral digits4 ,also1 as in the horses1 the elongation of the limbs began to be noteworthy while the body-weight was small and was consequently accompanied by great slenderness2 as the body-weight increased1 the limbs became stouter1 to yield the necessary support4 7#h7 ,in the phyla composed of massive animals the principle of change agreed with that exemplified by the titanotheres1 increasing body-weight being the determining factor in both cases4 ,when this increase began to be decided1 the reduction of digits ceased at the point which had already been reached in any particular series1 three in both manus and pes in the true rhinoceroses1 four in the manus and three in the pes in the amynodonts4 ,very heavy animals require broad1 columnar feet to support them1 and hence the similarity of appearance in such widely separated groups as elephants1 rhinoceroses and hippopotamuses1 not to mention several extinct orders and families4 ,among the larger and heavier rhinoceroses1 as in those of the present time1 there was great variety in the proportionate lengths of the limbs1 body and feet4 ,in brief1 the great complexity of the history of the rhinoceroses is due to the many divergent and parallel phyla into which these animals may be grouped4 ,broadly speaking1 they may be subdivided into the slender1 cursorial types and the heavy1 slow-moving types1 the former developing in a manner similar to that shown by the horses1 while the latter were modified after the fashion of the titanotheres4 ,obviously the load to be supported by the legs and feet was a very important factor in determining the character of evolutionary change4 ,,ii4 ,,ancylopoda4 ,,clawed ,,perissodactyls ,the very extraordinary and aberrant animals which are referable to this suborder have been understood only since the year #ahhh1 for1 as was shown in an earlier chapter 7p4 #da7 their scattered parts had been assigned to two different mammalian orders1 the skull to the perissodactyls and the feet to the pangolins1 or scaly anteaters 7,pholidota7 of the ,old ,world1 since it occurred to no one that the same animal could have such a skull and teeth in combination with such feet4 ,the history of the ,ancylopoda is still very incomplete1 only four genera1 of the lower ,pliocene1 middle and lower ,miocene1 and the middle ,eocene respectively1 being at all adequately known1 but even in this imperfect form the story is worth telling4 ,the suborder was probably of ,american origin and its most ancient known member existed in the middle ,eocene4 ,both in ,europe and ,north ,america the group persisted into the lower ,pliocene and it is believed1 though not clearly demonstrated1 that in eastern ,asia it continued even into the ,pleistocene4 ,all the genera of the suborder may be included in a single family4 #g4 ,chalicotheriid4 ,chalicotheres ,the specimens which so far have been found in the ,american middle and upper ,miocene and lower ,pliocene are very fragmentary1 consisting of little more than teeth1 and give no information other than to demonstrate the presence of the family in ,north ,america during that period of time4 ,on the other hand1 the ,european genera of the middle ,miocene and lower ,pliocene are well known and may or may not have been closely similar to their ,american contemporaries1 though they were undoubtedly larger4 ,in these most peculiar and grotesque animals 7,macrotherium and ,chalicotherium7 the head was relatively small1 the teeth were very low-crowned and adapted only to a diet of soft vegetable substances and the mode of feeding must have been that of browsing upon leaves and shoots of trees and bushes2 the premolars had not acquired the molar-pattern1 which was very exceptional for perissodactyls of so late a time1 such a difference between the two classes of teeth being characteristic of the ,eocene members of the order2 the incisors and canines were reduced1 but the formula is not definitely known4 ,the neck was of moderate length1 the body very long1 and the limbs were also elongate1 especially the anterior pair1 in consequence of which the back sloped downward from the shoulders to the rump2 the two fore-arm bones were fused together1 and these1 with the thigh-bones1 were the longest segments of the limbs4 ,the special peculiarity of these animals was in the character of the feet1 which had three toes1 each armed with a huge claw1 instead of terminating in a hoof1 as it does in all normal perissodactyls4 ,the external digit1 which1 in the absence of the fifth1 was the fourth1 was the largest of the series and apparently bore the most of the weight1 a notable departure from the normal perissodactyl symmetry1 in which the third or median toe is the largest4 ,the hind feet were considerably smaller than the fore1 but had similar claws4 ,many suggestions have been offered as to the manner in which these great claws were employed4 ,the teeth demonstrate that these animals could not have had predaceous habits1 but must have been inoffensive plant-feeders4 ,as no such herbivorous creatures are living now1 it is impossible to reach a definitive solution of the problem1 which is further complicated by the fact that in two other orders of hoofed mammals1 ,artiodactyla and ,toxodontia1 a more or less similar transformation of hoofs into claws took place1 and among the edentates the large1 herbivorous ground-sloths 7,gravigrada7 had enormous claws4 ,it is inadmissible to suppose that these great chalicotheres could have been burrowers1 or tree-climbers1 or that they pursued and slaughtered prey of any kind1 for1 aside from the character of the teeth1 such heavy and slow-moving beasts would have been utterly inefficient at work of that sort4 ,no doubt1 the claws were used1 to some extent1 as weapons of defence1 as the existing ,south ,american ,ant-,bear 7,myrmecophaga jubata7 uses his formidable claws2 probably also some1 if not all1 of these clawed ungulates would employ the fore feet in digging for roots and tubers1 as is done by the bears generally4 ,many years ago1 the late ,sir ,richard ,owen suggested with reference to the ground-sloths that the principal use of the fore feet1 other than that of locomotion1 was to draw down within reach of the long tongue and prehensile upper lip the branches upon which they browsed4 ,this explanation may perhaps be applicable to all of these aberrant and exceptional groups of hoofed animals4 ,illustration3 ,,fig4 #ahe4--,left manus of lower ,miocene chalicothere 7,moropus74 7,after ,peterson47 ,in the lower ,miocene 7,arikaree stage7 of ,north ,america well-nigh complete skeletons of a large chalicothere 7,moropus1 ,fig4 #acj1 p4 #bdj7 have been obtained1 an animal which considerably exceeded a large horse in bulk and stature4 ,in structure this genus had departed less widely from the normal perissodactyl type than the genera of the ,european ,miocene and ,pliocene above described and was in many respects more primitive4 ,it could not1 however1 have been directly ancestral to the ,european forms1 though indicating in a general sort of way what the ancestral type must have been4 ,moropus had a relatively small1 slender and pointed head1 a long neck1 much longer than in the ,european genera1 and long fore legs2 the shorter hind legs gave the back a steep inclination from the shoulders to the rump4 ,the proportions of the head1 neck and limbs suggest those of a giraffe1 in less exaggerated form1 but the likeness is more marked in the skeleton than in the restoration and is at best a distant one4 ,the feet were armed with the great claws characteristic of the suborder1 but the fore foot1 in addition to the three functional toes1 had a long splint1 representing the rudimentary fifth digit2 of the first1 or pollex1 no trace remained4 ,the perissodactyl plan of symmetry had not yet been lost1 the third or median digit being the longest of the series4 ,in the hind foot1 which had only three toes1 the departure from the perissodactyl arrangement had already begun1 and the third and fourth digits 7i4e4 of the original five7 were of nearly equal size1 both in length and thickness1 while the second was smaller4 ,the family is represented in the ,john ,day1 or upper ,oligocene1 by specimens which are sufficiently characteristic to prove that they are properly referable to this group4 ,they have been assigned to the same genus as that of the lower ,miocene1 but whether the identification is justified remains to be determined4 ,in the lower ,white ,river beds of ,canada is found a much smaller animal of this family1 but the material is too fragmentary for generic identification4 ,something more is known of a genus 7,schizotherium7 from the ,european ,oligocene1 likewise much smaller than the ,miocene and ,pliocene forms1 which had four1 or possibly even five1 functional digits1 in the manus1 but it has not been ascertained whether the transformation of hoofs into claws had already taken place4 ,it is not yet practicable to determine the relationships of the ,european and ,american chalicotheres to one another1 because of the imperfect nature of most of the material4 ,the molar teeth of the chalicotheres were suggestively like those of the titanotheres1 and1 were the teeth alone to be taken into account1 no one could hesitate to regard the two families as closely related4 ,the most ancient known member of the family is the genus ,eomoropus1 from the ,bridger ,eocene1 which will be described by ,professor ,osborn in a paper soon to appear4 ,eomoropus was much nearer to the normal perissodactyls than were the genera from the ,oligocene and ,miocene above described4 ,,chapter ,,ix ,,history ,,of ,,the ,,artiodactyla ,the artiodactyls are and for a very long time have been a very much larger and more variegated group than the perissodactyls1 and the ,old ,world has been and still is their headquarters and area of special development1 where they are represented in far greater number and variety than in the ,new2 the perissodactyls1 on the other hand1 flourished especially in ,north ,america1 as was shown in the preceding chapter4 ,at the present time the artiodactyls are the dominant ungulate order1 far outnumbering all the others combined1 and include an assemblage of varied types1 which1 when superficially examined1 appear to be an arbitrary and unnatural group4 ,what could seem more unlike than a dainty little mouse-deer1 no larger than a hare1 a stag1 a camel1 a giraffe1 a bison and a hippopotamus8 ,yet1 in spite of this wonderful diversity of size1 proportions1 appearance and habits1 there is a genuine unity of structure throughout the order1 which makes their association in a single group altogether natural and proper1 especially as these structural characters are not found united in any other group4 ,it would be superfluous to enumerate all of the diagnostic characters which1 on the one hand1 unite all the living and extinct artiodactyls and1 on the other1 distinguish them from all other hoofed animals1 and it will suffice to mention a few of the more significant of these features4 ,as the name implies1 the artiodactyls typically have an even number of toes in each foot1 four or two2 though this rule may be departed from and we find members of the order with five digits or three1 just as the tapirs and nearly all the ,eocene genera of perissodactyls had four toes in the manus4 ,much more important is the fact that the plane of symmetry1 which in the perissodactyls bisects the third digit and is therefore said to be mesaxonic1 passes between the third and fourth digit and is paraxonic4 ,the third and fourth digits always form an equal and symmetrical pair and are the 8irreducible minimum10 beyond which the number of toes cannot be diminished4 ,a single-toed artiodactyl would seem to be an anatomical impossibility2 at all events1 such a monstrosity was never known4 ,hence the term 8cloven0 or 8divided0 hoof1 which seems to take the solid hoof of the horse as the norm2 but 8cloven or divided10 while expressing the appearance of the foot with sufficient accuracy1 is erroneous1 if taken to mean the splitting of what was once continuous4 ,illustration3 ,,fig4 #ahf4--,left fore-arm bones of the ,domestic ,pig 7,sus scrofa74 ,r41 radius4 ,u41 ulna4 ol41 olecranon4 ,illustration3 ,,fig4 #ahg4--,left manus of ,pig4 ,s41 scaphoid4 ,l41 lunar4 ,py41 pyramidal4 ,pis41 pisiform4 ,td41 trapezoid4 ,m41 magnum4 ,u41 unciform4 ,mc4 ,i1 second1 ,mc4 ,,ii1 third1 ,mc4 ,,iii1 fourth1 ,mc4 ,,iv1 fifth1 metacarpals4 ,illustration3 ,,fig4 #ahh4--,left pes of ,pig4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cb41 cuboid4 ,cn4 #b1 ,cn4 #c1 second and third cuneiforms4 ,mt4 ,,ii-,v1 second to fifth metatarsals4 ,illustration3 ,,fig4 #ahi4--;,bunodont upper molar of peccary 7,tagassu74 ,illustration3 ,,fig4 #aij4--,selenodont upper molar of deer 7,odocoileus74 ,especially characteristic of the order is the structure of the ankle1 or 8hock-joint0 of the hind limb4 ,the ankle-bone1 or astragalus1 has a double pulley1 the upper and lower ends being of quite similar shape2 its lower end is almost equally divided between the cuboid and navicular1 which are made concave to receive it4 ,this type of astragalus is altogether peculiar to the artiodactyls1 all of which possess it2 it is unlike that of any other mammal whatever and may be recognized at a glance4 ,the calcaneum1 or heel-bone1 has a large convex facet1 by means of which it articulates with the fibula1 or external leg-bone2 there is no such articulation in the perissodactyls4 ,the lower end of the calcaneum is narrow and fits into a step cut in the cuboid1 which is thus every whit as peculiar and characteristic as the calcaneum and astragalus4 ,the femur never has the third trochanter1 which is always present in the perissodactyls4 ,another respect in which the artiodactyls differ from all perissodactyls except the horses is in the much more complex mode of articulation between the vertebr of the lumbar and posterior dorsal regions1 which the former display1 and even the horses have no such elaborate arrangement4 ,finally1 another very marked difference from the perissodactyls is in the teeth1 for the premolars and molars are never alike1 and only in very rare instances does the last premolar assume the molar-pattern4 ,of this pattern1 there are two principal kinds1 one exemplified by the peccaries1 in which the crown supports a series1 fundamentally two pairs1 of conical cusps1 and called bunodont1 and the other1 to be seen in all the ruminating animals1 in which the crown is composed of two pairs of crescents and is therefore said to be selenodont4 ,the bunodont was the primitive type1 whence the other was derived1 and many transitional forms are known4 ,the classification of the immense horde of living and extinct genera and species which are referable to the artiodactyls is an extremely difficult problem1 which has found no thoroughly satisfactory solution and will not until much more is learned concerning the history of the order and conflicting opinions can be reconciled4 ,the most important ,american families and genera are given below1 though the arrangement is but tentative4 ,suborder ,a4 ,,artiodactyla ,,primitiva4 7,extinct genera of doubtful affinities7 ,i4 ,,trigonolestid4 ,trigonolestes1 low4 ,eoc4 ,,ii4 ,,leptoch,,rid4 ,leptochrus1 low4 ,oligo4 ,stibarus1 low4 ,oligo4 ,,iii4 ,,dichobunid4 ,homacodon1 mid4 ,eoc4 ,bunomeryx1 up4 ,eoc4 ,,iv4 ,,anthracotheriid4 ,anthracotherium1 low4 ,oligo4 ,bothriodon1 do4 ,arretotherium1 do4 ,v4 8,,oreodontid4 ,protoreodon1 up4 ,eoc4 ,merycoidodon1 low4 ,oligo4 ,eporeodon1 up4 ,oligo4 ,promerycochrus1 up4 ,oligo4 to up4 ,mioc4,merycochrus1 ,mioc4 and low4 ,plioc4 ,pronomotherium1 up4 ,mioc4 ,mesoreodon1 low4 ,mioc4 ,merychyus1 low4 ,mioc4 to low4 ,plioc4 ,leptauchenia1 low4 ,oligo4 to low4 ,mioc4 ,cyclopidius1 mid4 ,mioc4 ,,vi4 ,,agrioch,,rid4 ,protagriochrus1 up4 ,eoc4 ,agriochrus1 ,oligo4 ,suborder ,b4 ,,suina4 ,swine-like ,animals ,,vii4 ,,tagassuid1 ,peccaries4 ,helohyus1 mid4 ,eoc4 ,perchrus1 low4 ,oligo4 ,thinohyus1 up4 ,oligo4 ,desmathyus1 low4 ,mioc4 ,prosthennops1 up4 ,mioc4 and low4 ,plioc4 ,platygonus1 mid4 ,plioc4 to ,pleist4 ,tagassu1 ,recent1 ,pleist4 in ,s4 ,a4 ,,viii4 ,,entelodontid4 ,giant ,pigs4 ,parahyus1 low4 ,eoc4 ,achnodon1 mid4 and up4 ,eoc4 ,arcotherium1 low4 ,oligo4 ,bochrus1 up4 ,oligo4 ,dinohyus1 low ,mioc4 ,suborder ,c4 ,,tylopoda4 ,camels and ,llamas ,,ix4 ,,camelid4 ,protylopus1 up4 ,eoc4 ,eotylopus1 low4 ,oligo4 ,pobrotherium1 ,oligo4 ,pseudolabis1 low4 ,oligo4 ,protomeryx1 up4 ,oligo4 and low4 ,mioc4 ,oxydactylus1 low4 ,mioc4 ,miolabis1 mid4 ,mioc4 ,protolabis1 mid4 and up4 ,mioc4 ,alticamelus1 mid4 ,mioc4 to low4 ,plioc4 ,stenomylus1 low4 ,mioc4 ,procamelus1 up4 ,mioc4 and low4 ,plioc4 ,pliauchenia1 up4 ,mioc4 to mid4 ,plioc4 ,camelus1 ,pleist4 ,lama1 ,plioc4 to ,recent1 ,s4 ,a4 ,x4 ,,hypertragulid4 ,leptotragulus1 up4 ,eoc4 ,leptoreodon1 up4 ,eoc4 ,leptomeryx1 low4 ,oligo4 ,hypertragulus1 ,oligo4 ,hypisodus1 low4 ,oligo4 ,protoceras1 low4 ,oligo4 ,syndyoceras1 low4 ,mioc4 ,suborder ,d4 ,,pecora4 ,true ,ruminants ,,xi4 ,,cervid4 ,deer4 ,blastomeryx1 low4 ,mioc4 to low4 ,plioc4 ,cervus1 ,pleist4 and ,rec4 ,rangifer1 ,pleist4 and ,rec4 ,alce1 ,pleist4 and ,rec4 ,cervalces1 ,pleist4 ,odocoileus1 ,pleist4 and ,rec41 ,n4 and ,s4 ,a4 ,mazama1 ,pleist4 to ,rec41 ,s4 ,a4 ,,xii4 ,,merycodontid4 ,deer-,antelopes4 ,merycodus1 mid4 ,mioc4 to low4 ,plioc4 ,capromeryx1 ,pleist4 ,,xiii4 ,,antilocaprid4 ,prong-,bucks4 ,antilocapra1 ,pleist4 and ,rec4 8,dromomeryx1 mid4 and up4 ,mioc4 ,,xiv4 ,,bovid4 ,antelopes1 ,sheep1 ,goats1 ,oxen1 etc4 ,neotragocerus1 ,ilingoceros1 ,sphenophalus1 low4 ,plioc4 ,preptoceras1 ,euceratherium1 ,symbos1 ,pleist4 ,ovibos1 ,pleist4 and ,rec4 ,bison1 ,pleist4 and ,rec4 ,this list of families and genera1 portentous as it is1 would be greatly increased by the addition of the ,old ,world forms1 which outnumber those of the western hemisphere4 ,,suborder ,,suina4 ,,swine-,,like ,,animals ,the history of the ,american types of pig-like forms is1 in one sense1 very full and complete in that the successive genera may be traced back to the ,eocene1 but1 in another sense1 the story is exasperatingly imperfect1 because so much of the material is fragmentary4 ,of most of the genera1 nothing is known but teeth and jaws1 and these1 though sufficient for identification1 tell but little of the structural changes which it is desirable to know4 ,it is merely a question of time1 when more adequate material will be obtained4 #a4 ,tagassuid4 ,peccaries ,the peccaries1 or ,american swine1 are now chiefly of ,neotropical distribution1 extending into the ,sonoran region only as far as ,arkansas2 but this has been true only since the ,pleistocene1 for nearly the entire history of the family has been enacted in ,north ,america4 ,in many points of structure the peccaries of the present day are more advanced and specialized than the far more varied and diversified true swine of the ,old ,world1 for it is a singular fact that such a long-lived and persistent stock as the peccaries should have given rise to so few variants and side-branches4 ,existing peccaries all belong to a single genus 7,tagassu7 and are relatively small animals1 of unmistakably pig-like character and appearance1 but far smaller than the ,wild ,boar 7,sus scrofa7 of ,europe1 or the ,wart ,hog 7,phacochrus thiopicus7 of ,africa1 to mention only two of the ,old ,world swine4 ,illustration3 ,,fig4 #aia4--;,dentition of the ,collared ,peccary 7,tagassu tajacu7 left side4 i #c1 external incisor4 ,c1 canine1 p #b1 second premolar 7the first is lost71 m #a1 first molar4 ,one characteristic and thoroughgoing difference between the peccaries and the swine is the shape of the canine tusks4 ,in the former1 the tusks1 though very effective weapons1 are not very large and are straight and have a vertical direction1 while in all the true swine the upper tusk is curved upward and outward1 projecting strongly from the side of the jaw1 and the great1 curved lower tusk wears against its anterior side4 ,the peccaries further have smaller and simpler molars1 each with four principal1 conical cusps 7quadrituberculate pattern7 arranged in two transverse pairs1 with numerous very small cuspules around and between them1 obscuring the plan4 ,in the true swine the teeth are much larger and covered with innumerable wart-like cusps1 large and small1 seldom arranged according to any definite plan4 ,in the following particulars the modern peccaries show advance over the ,old ,world swine3 7#a7 the last lower premolar has taken on the molar-pattern1 a very exceptional feature among the artiodactyls2 7#b7 the ulna and radius are cossified2 7#c7 there are but two functional digits in each foot2 the fore foot has1 in addition1 two complete1 but very reduced and slender1 lateral digits and the hind foot only one1 whereas in all the pigs of the eastern hemisphere there are four functional toes in each foot2 7#d7 in the hind foot the two functional metatarsals1 the third and fourth1 have coalesced to form a 8cannon-bone10 a structure which is not found in any other family of the suborder2 7#e7 the stomach is complex1 approximating that of a ruminant4 ,in the ,north ,american ,pleistocene the predominating kind of peccary was a genus 7,platygonus7 which was more advanced than the existing form 7,tagassu71 and1 to all seeming1 better fitted to survive1 though for some inexplicable reason it failed to do so4 ,it was a considerably larger animal1 with proportionately longer and heavier legs4 ,its molar teeth are of special interest because they reproduced a type which has been so often repeated and independently acquired in so many different groups of mammals4 ,in this molar the two conical cusps of each pair were fused into a high1 transverse ridge or crest4 ,precisely the same modification took place among the true swine in the genus ,listriodon of the ,french middle ,miocene4 ,platygonus first appeared in the middle ,pliocene1 and its predecessor in the lower ,pliocene and upper ,miocene showed the crests of the molars in process of formation4 ,in the latter stage it was accompanied by a true peccary with tuberculated teeth1 which differed from the modern species in the simplicity of the hindmost premolar1 which had not taken on the molar-pattern4 ,if the feet and limbs of this upper ,miocene peccary were known1 they would doubtless prove to be much more primitive than those of ,tagassu1 but they still await discovery4 ,little can be said of the peccaries of the middle and lower ,miocene other than to record the fact of their presence in those formations1 but those of the upper ,oligocene 7,john ,day7 are1 however1 represented by well-preserved skulls1 which show that more than one phylum of the family had arisen1 though there was no great difference between them2 they were considerably smaller animals than those of the ,pliocene and ,pleistocene4 ,still smaller was the ,white ,river genus 7,perchrus7 of which some fragmentary skeletons have been obtained4 ,although an undoubted peccary1 this animal was not far from what the common progenitor of the peccaries and the true swine might be expected to resemble4 ,the molars were quadrituberculate without the numerous accessory cuspules of the modern genus2 the bones of the fore-arm were separate and the feet had four functional digits each1 while there was no cannon-bone in the pes1 the metatarsals remaining free4 ,no peccaries have yet been found in the ,uinta1 but probably this is a mere accident of collecting4 ,it is1 however1 possible that the ,white ,river genus was not of ,american derivation1 but an immigrant from the ,old ,world4 ,in the middle ,eocene1 or ,bridger stage1 this series is known only from teeth and jaws and a very few scattered foot-bones1 and these1 though probably referable to the family1 cannot be definitively assigned to it without more complete material4 ,several species1 larger and smaller1 of the genus ,helohyus occurred in the ,bridger1 where they were not uncommon1 considering the general rarity of artiodactyls in that stage4 ,thus1 the peccaries1 though none of them were large1 followed the usual law of mammalian development1 and1 beginning with very small forms1 increased in size with each succeeding geological stage down to the ,pleistocene4 #b4 ,entelodontid4 ,giant ,pigs ,the giant pigs1 a most remarkable group of swine-like forms and of as yet unknown origin1 appeared for the last time in ,north ,america in the lower ,miocene1 where the genus of that date 7,dinohyus7 was the largest of known suilline animals1 the hippopotamuses excepted4 ,in nearly every part of the skeleton these great beasts displayed an unusual and aberrant kind of development4 ,the incisors were long and pointed1 and the canines formed stout and heavy1 though not very long1 tusks1 which in shape were more like those of a bear than those of either peccaries or swine4 ,the premolars were very simple1 of compressed conical and trenchant shape1 and occupied a very long space in the jaws1 while the molars were relatively small and quadrituberculate1 the crowns covered with very thick1 coarsely wrinkled enamel4 ,the skull was immensely elongate1 especially the facial region in front of the eyes1 while the brain-case was so absurdly small as to give the skull a reptilian aspect1 when viewed from above4 ,evidently1 these great pigs were profoundly stupid1 in this respect rivalling the titanotheres of the ,white ,river 7p4 #caa74 ,beneath each eye-socket was a long1 descending1 bony flap1 or process1 and on the under side of the lower jaw were two pairs of prominent knobs1 the function of which1 as of the flaps beneath the eyes1 is quite problematical4 ,the eye-sockets themselves were completely encircled in bone1 a rare character in the suborder4 ,the neck was short1 as in the pigs generally1 the body not very elongate and the tail of moderate length2 at the shoulders1 the spines of the dorsal vertebr were very long1 making a decided hump1 and in the lumbar and posterior dorsal region the processes for articulation between the vertebr were extremely elaborate4 ,for one of the pigs1 the limbs were very long and gave quite a stilted look to the animal4 ,as in the modern peccaries1 the fore-arm bones were indistinguishably fused together and the feet had only two toes each1 the only members of the suborder in which digital reduction had proceeded so far1 though the existing peccaries approximate this condition4 ,there were1 however1 nodular vestiges of two other digits1 which prove the derivation of this form from at least a four-toed type2 no cannon-bone was formed4 ,in view of the size of the animal1 the hoofs were surprisingly small1 which suggests that the weight was chiefly borne upon a pad4 ,dinohyus was a very large animal1 six feet or more in height at the shoulder4 ,illustration3 ,,fig4 #aib4--,right manus of entelodont 7,archotherium ingens7 from lower ,white ,river beds4 ,princeton ,university ,museum4 ,illustration3 ,,fig4 #aic4--,skull of ,white ,river entelodont 7,archotherium mortoni74 ,princeton ,university ,museum4 ,for restoration1 see ,fig4 #acg1 p4 #bfj4 ,in the upper ,oligocene were very large species of another1 but closely similar1 genus 7,bochrus7 though somewhat smaller than those of ,dinohyus1 and the species of the upper ,white ,river beds 7,archotherium7 were little1 if at all1 smaller than those of the ,john ,day4 ,a number of specimens in the museum of ,princeton ,university throw a welcome light upon the habits of these strange creatures4 ,in one1 the external1 or third1 upper incisor tooth has a deep1 triangular notch worn in its postero-external face1 and the lower canine has a well-defined groove worn on the posterior side at the base of the crown2 other individuals show less distinct marks of similar kind4 7,see ,fig4 #aid47 ,it is out of the question to suppose that these grooves and notches could have been produced by abrasion with other teeth1 for no other teeth could reach the worn areas1 and it is altogether probable that they were made in digging up roots4 ,the root1 held firmly in the ground at both ends and looped over the teeth which pulled until it broke1 and being covered with abrasive grit1 would wear just such marks as the teeth actually display4#g ,while the entelodonts were thus rooters1 they were doubtless omnivorous1 like other pigs1 and did not disdain a meal of carrion when they could get it4 ,it is likely that the heavy canine tusks were also used as weapons1 both in defence against the attacks of carnivores and in fighting between the males of the same species4 ,it must have been in some such encounter that the animal represented by a complete skeleton in the ,princeton ,museum received its broken rib2 that the fracture was made during life is demonstrated by the large callus growths on the broken ends1 but the pieces did not knit4 ,illustration3 ,,fig4 #aid4--,specimen showing characteristic grooves of wear in the anterior teeth of entelodont 7,archotherium7 from upper ,white ,river beds4 ,princeton ,university ,museum4 ,in the middle and lower substages of the ,white ,river the genus 7,archotherium7 was the same as in the upper substage of these beds1 but the species were all smaller and some of them very much so1 not exceeding an ordinary pig in size4 ,throughout the series1 as we now have it1 from the lower ,oligocene into the lower ,miocene1 there is very little change except in size1 all the essential features of structure remaining the same2 the genera are therefore distinguished by modifications of very secondary importance1 and it is a question whether all the species should not be included in a single genus4 ,the ,european genus ,entelodon1 which gives its name to the family1 is so like the ,american forms that by most writers the ,white ,river species are referred to it4 ,it is of interest to note that the giant pigs have also been found in the marine ,miocene of ,new ,jersey1 one of the few records of the ,tertiary land mammals of the ,atlantic seaboard4 ,at present1 the entelodonts proper cannot be traced back of the lower ,white ,river beds1 nor are they found in any more ancient formations in ,europe4 ,it is1 therefore1 probable that they were immigrants in both of these continents1 presumably from ,asia4 ,illustration3 ,,fig4 #aie4--,skull of short-faced pig 7,achnodon robustus7 from the ,bridger ,eocene4 ,princeton ,university ,museum4 ,the whole ,eocene of ,north ,america had a series of pig-like animals1 called the achnodonts or short-faced pigs1 which seem to have been related to the entelodonts4 ,they ended their career in the ,uinta just before the appearance of the entelodonts1 and it would be natural to suppose that the latter were descended from them4 ,if1 however1 the principle that an organ or structure once lost can never be regained1 is valid1 then there can be no relation of ancestor and descendant between the two groups1 for of the achnodonts1 even their most ancient representatives had lost the first premolar1 giving the formula p #c_/c1 while in the entelodonts it is constantly p #d_/d4 ,the achnodonts1 which are much less fully known than the entelodonts1 had teeth very similar in form to those of the latter2 and their most conspicuous feature was the shortness of the face and jaws1 as contrasted with the extreme elongation of these parts in the entelodonts1 nor did they have the bony flaps under the eyes or the knobs on the lower jaw which gave such a fantastic appearance to the entelodont skull4 ,little is known of the skeleton except that there were four functional digits in the manus4 ,the ,uinta and ,bridger genus 7,achnodon7 was larger than the ,wasatch form 7,parahyus71 which was an immigrant1 probably from the same region as afterwards sent out the entelodonts to ,america and ,europe2 this would account for the similarity and probable relationship of the two subfamilies4 ,,suborder ,,artiodactyla ,,primitiva4 ,,primitive ,,artiodactyls ,no doubt1 this suborder is an artificial assemblage of unrelated families1 a sort of waste-basket1 into which are thrown the groups of which no other disposition can be made in the present state of knowledge4 ,as information becomes more complete1 the various families will be redistributed among the groups with which they had a genuine relationship4 #c4 ,anthracotheriid4 ,anthracotheres ,this family was abundantly represented in ,europe from the middle ,eocene through the ,oligocene1 in ,asia persisting even into the ,pliocene1 and were abundant in the ,oligocene of ,egypt4 ,migrants from the ,old ,world reached ,america in ,white ,river times1 but speedily died out1 as they did not survive into the upper ,oligocene4 ,the most fully known of these animals is an ,american species of a ,european genus ,bothriodon4 ,almost complete skeletons of this genus have been obtained in the channel sandstones of the upper ,white ,river substage4 ,in size and proportions1 ,bothriodon was not unlike a domestic pig1 but had a very long head with slender1 pointed snout2 it had also a short neck1 long body1 short limbs and feet4 ,the primitive character of this genus is made clear by many features of its structure2 the molar teeth were extremely low-crowned and their cusps were so imperfectly crescentic in form as to be called buno-selenodont1 as indicating their transitional nature1 and the upper molars had five cusps instead of four1 a very primitive feature4 ,another very significant character was the five-toed manus2 the first digit1 or pollex1 was much smaller than the others4 ,illustration3 ,,fig4 #aif4--;,bothriodon brachyrhynchus1 upper ,white ,river stage4 ,restored from a skeleton in the museum of ,princeton ,university4 ,the second genus of the family which had ,american representatives was ,anthracotherium1 which was much like ,bothriodon1 but even more archaic in character2 the molars could hardly be called selenodont at all4 #d4 ,oreodontid4 ,oreodonts ,this was one of the most characteristic of ,north ,american artiodactyl families1 and its members were exceedingly abundant throughout the upper ,eocene1 the whole ,oligocene and ,miocene1 ending their long career in the lower ,pliocene4 ,in distribution the family was exclusively ,north ,american1 and no trace of it has been found in any other continent4 ,in the course of their long history the oreodonts underwent many transformations and branched out into several distinct phyla1 yet through all these changes they remained singularly conservative1 for the transformations1 some of them sufficiently bizarre1 affected chiefly the teeth and skull1 the remainder of the skeleton changing but little4 ,the oreodonts were all small or of moderate size1 none of them surpassing the ,wild ,boar in stature1 nor was there any decided increase in size from stage to stage4 ,one and all1 they were strange beasts4 ,dr4 ,leidy1 who first described and named most of the genera1 spoke of them as combining the characters of camel1 deer and pig1 and called them 8ruminating hogs10 a conception expressed in the names which he gave to some of them1 such as ,merychyus and ,merycochrus1 both of which mean ruminant swine4 ,the general proportions of most of the species were quite as in the peccaries1 though1 for the most part1 with much longer tails2 they had a short neck1 elongate body1 short limbs and feet4 ,in one genus 7,mesoreodon7 of the lower ,miocene a rudimentary collar-bone has been found1 and probably all of the more ancient genera possessed it1 but only by an unusually lucky chance would so small and loosely attached a bone be preserved in place4 ,as the collar-bone is superfluous in hoofed animals1 in which the limbs are used only for locomotion and move in planes parallel with that of the backbone1 it is almost universally absent in them1 and in only one other group of ungulates1 the extinct ,typotheria of ,south ,america1 has its presence been demonstrated4 ,in all of the oreodonts the bones of the fore-arm and lower leg remained separate4 ,the teeth were in continuous series1 and there was a peculiar feature in the dentition common to nearly every one of the genera4 ,on casual examination1 one would say that the animals had four lower incisors on each side and that the lower canine closed behind the upper one1 a most exceptional arrangement4 ,more careful study shows that the apparent fourth incisor was the canine1 a transformation which has also taken place in all of the ruminants except the camels1 and the tooth which had assumed the form and function of the lower canine was really the first lower premolar2 this latter change is not found among the ruminants1 but was repeated in a few other extinct families4 ,illustration3 ,,fig4 #aig4--;,head of ,merycochrus proprius1 lower ,miocene to lower ,pliocene4 ,restored from a skull in the ,american ,museum of ,natural ,history4 ,only two genera of oreodonts 7,merychyus and ,merycochrus7 survived into the lower ,pliocene4 ,both had the proportions common throughout the family1 but ,merychyus was much more slender and lightly built1 its lateral digits were reduced in size and very thin and it had hypsodont grinding teeth2 while ,merycochrus was of larger size 7about that of a large domestic pig7 and stouter build and had low-crowned teeth2 its head1 however1 had a very different appearance1 given by the possession of a short proboscis1 the presence of which is indicated by the greatly reduced nasal bones2 the jaws and face were also much shortened4 ,the eye-sockets presented obliquely forward and upward1 instead of laterally1 as is usual among mammals1 and were placed high in the head4 ,this position of the eyes and of the entrance to the ear renders it probable that ,merycochrus was largely aquatic in its habits4 ,both genera had short1 four-toed feet1 as was general throughout the family and in no genus did the reduction of digits proceed beyond the loss of the first of the original five1 the pollex and hallux4 ,the two genera above described1 representatives of two distinct phyla within the family1 held over1 as it were1 from the upper ,miocene without essential change4 ,the phylum of the hypsodont and slender ,merychyus went back1 with only minor modifications1 into the upper substage of the lower ,miocene1 but cannot as yet be traced to an ,oligocene ancestry2 it is therefore still impossible to say just where and when it branched off from the main stem of the family4 ,future discoveries in the ,oligocene will no doubt clear up this problem4 ,the real terminal and most highly specialized member of the ,merycochrus phylum and the most extraordinary member of the entire family was confined to the upper ,miocene4 ,the extreme peculiarity of this genus 7,pronomotherium7 was displayed only in the head1 which was an exaggeration of the ,merycochrus type1 the face being excessively shortened and the nasals so reduced as to show that the proboscis was much better developed than in the parent genus4 ,the shortening of the face and the great vertical height of the skull and lower jaw gave a decided likeness to the skull of a great ape1 though the proboscis would mask any such resemblance in the living head4 ,merycochrus itself went back to the upper division of the lower ,miocene1 but in the lower division it was replaced by an ancestral genus1 ,promerycochrus1 which had an elongate face and jaws and no proboscis2 but in other characteristic features1 such as the extreme thickness and roughness of the zygomatic arches1 it was like its descendant4 ,promerycochrus contained the largest known species of oreodonts1 some of them equalling a ,wild ,boar in stature1 and its remains are found so abundantly in the middle and lower ,miocene and upper ,oligocene1 that there must have been great herds of these animals over the plains4 ,probably it was itself derived from some of the larger species of ,eporeodon of the upper ,white ,river beds1 but there is a gap in the history1 due to the fact that the lower part of the ,john ,day is almost barren of fossils and the connecting link has not been recovered4 ,illustration3 ,,fig4 #aih4--;,head of ,pronomotherium laticeps1 upper ,miocene4 ,restored from a skull in the ,carnegie ,museum1 ,pittsburgh4 ,it is an interesting and significant fact that ancestral and derivative genera may continue to live side by side in the same region4 ,promerycochrus1 it is believed1 gave rise to ,merycochrus1 but survived with it into the middle ,miocene4 ,merycochrus1 in its turn1 produced ,pronomotherium1 and1 so far from being replaced by the latter1 actually outlived it and persisted into the lower ,pliocene4 ,illustration3 ,,fig4 #aii4--,promerycochrus carrikeri1 lower ,miocene4 ,restored from a skeleton in the ,carnegie ,museum1 ,pittsburgh4 ,a third phylum of the oreodonts1 which appeared for the last time in the middle ,miocene 7genus ,cyclopidius71 was a series of small and very small species1 of which the skull was almost as peculiar as that of ,pronomotherium1 but in a different fashion4 ,the face was very much shortened and on each side a great vacuity reduced the nasal bones to mere splints2 the elevated position of the eye-sockets1 which projected above the forehead1 and of the tubular entrance to the ear is an evidence of an aquatic or amphibious mode of life1 such as is illustrated by the hippopotamuses1 which can float almost completely submerged1 with only the ears1 eyes and nostrils above the surface of the water4 ,the tympanic bull 7see p4 #ff7 or bony chambers into which the ear-tubes opened1 were of relatively enormous size and added much to the unusual appearance of the skull4 ,the incisors were very small and the grinding teeth narrow and completely hypsodont1 this and the ,merychyus series being the only two phyla of the family in which the hypsodont molar was fully acquired4 ,the remainder of the skeleton differed but little from the type common to the whole family1 except for a somewhat shorter tail4 ,illustration3 ,,fig4 #bjj4--,skull of ,leptauchenia nitida1 upper ,white ,river4 ,the animals of this series were common in the middle and lower ,miocene and in the upper substage of the ,white ,river1 but have not been found in the intermediate ,john ,day4 ,this may have been a matter of geographical distribution1 these creatures not extending west of the main ranges of the ,rocky ,mountains4 ,in the upper ,white ,river the genus ,leptauchenia is extremely common1 but below that level they suddenly and completely vanish and1 as in the case of the ,merychyus phylum1 it is not yet practicable to determine the point in time or space of their branching off from the main stem of the family4 ,were the oreodonts not entirely confined to ,north ,america1 we should1 as a matter of course1 explain the seemingly sudden appearance of ,leptauchenia as due to immigration1 and it is entirely possible that the series did actually originate in some part of ,north ,america which has left no record of its ,eocene or ,oligocene terrestrial life4 ,on the other hand1 no one can imagine that everything that can be known of the mammals of the middle and lower ,white ,river has already been learned1 and at any time the sought-for ancestor of ,leptauchenia may be found in those beds4 ,illustration3 ,,fig4 #bja4--,leptauchenia nitida1 upper ,white ,river4 ,restored from a skeleton in the ,museum of ,princeton ,university4 ,the fourth phylum may be regarded as the main or central stem of the family and was the one which underwent the least change1 though it probably gave rise to all the other phyla1 which branched off from it at various stages in its history4 ,this series terminated in the middle ,miocene and comprised several genera1 all very much alike1 in the lower stages of that epoch4 ,one of these genera 7,mesoreodon7 displayed a very remarkable peculiarity of structure in the ossification of the great cartilage of the larynx1 which seems to point to the possession of uncommon vocal powers4 ,it is impossible to say whether this feature was confined to the single genus1 or was general in the family1 for only in rare instances would so extremely delicate a structure be preserved4 ,in the ,john ,day the genus ,eporeodon1 which was very abundant1 was the representative of this phylum1 and the same1 or a closely similar1 genus lived in the latter part of the ,white ,river stage4 ,in the middle and lower ,white ,river substages oreodonts are the commonest of fossils1 so that the collector soon wearies of them 7see ,fig4 #acf1 p4 #bei72 they must have lived in great herds in the forests and along the streams4 ,there were several species1 varying principally in size1 the largest about as long as a wolf1 but with shorter legs1 and the smallest not so much as half of that size4 ,all belonged to a single genus1 for which the rigid law of priority compels us to use a most cumbrous name 7,merycoidodon71 the widely used term ,oreodon being a synonym4 ,this genus was the central stock of the family1 from which most1 if not all1 the others were directly or indirectly derived1 though1 as previously pointed out1 we cannot in all cases trace the connection4 ,in these ,white ,river animals the grinding teeth were very low-crowned and had considerable resemblance to those of a deer2 the molars were typically selenodont and made up of two pairs of crescentic cusps4 ,the skull differed little from that of the succeeding genera of this phylum2 the neck was short1 body and tail long4 ,an especially interesting fact is that the fore foot had five digits1 the first1 or pollex1 very small and of no functional value1 but complete in all its parts2 the hind foot was four-toed4 ,in all of the subsequent genera of the family the number of digits was uniformly four in both manus and pes4 ,illustration3 ,,fig4 #bjb4--,skull of ,merycoidodon culbertsoni1 middle ,white ,river4 7,after ,leidy47 ,in the ,uinta stage of the upper ,eocene lived the most ancient and primitive member of the family yet discovered1 the genus ,protoreodon1 which is in every respect what the ancestor of the ,white ,river genus should be4 ,the functional transformation of the lower canine into a fourth incisor and the replacement of the canine by the first lower premolar had already taken place1 but the molars were much more primitive than those of the ,white ,river and succeeding genera2 the crescents were thicker and less complete1 plainly indicating their derivation from conical cusps1 and a small fifth cusp was present between the anterior pair of the upper molars1 as in the anthracotheres and other ,european families of the ,artiodactyla ,primitiva4 ,before the discovery of ,protoreodon1 the character of its molars was predicted by ,dr4 ,schlosser1 of ,munich4 ,the skull resembled that of the ,white ,river genera1 except that the eye-socket was open behind1 and there was no glandular pit in front of the eye4 ,the skeleton is but partially known1 but it has been ascertained that there were five toes in the manus and probably also in the pes4 ,illustration3 ,,fig4 #bjc4--,skull of ,protoreodon parvus1 ,uinta ,eocene4 ,princeton ,university ,museum4 ,n4,b4 ,this skull is actually much smaller than that shown in ,fig4 #bjb4 ,nothing has yet been discovered in formations older than the upper ,eocene which can be regarded as ancestral to the oreodonts1 and this is not surprising in view of the extremely meagre and unsatisfactory nature of our information regarding the artiodactyls of the ,bridger4 ,on the whole1 however1 it seems rather more probable that the ,uinta genus was an immigrant 7whence1 we cannot say7 than that the ,bridger will ever yield the desired ancestral forms4 ,so long as the early ,tertiary mammals of northern and central ,asia remain unknown1 this and many similar problems can find no definitive solution4 ,the question of relationship with other families is bound up with that of the origin of the oreodonts2 many characters point to a connection with the anthracotheres and1 from the standpoint of present knowledge1 that appears to be the most probable affinity2 but1 on the other hand1 there are structural features which suggest relationship with the primitive camels4 ,between these and other alternatives1 only the recovery of the middle and lower ,eocene forms can finally decide4 ,reviewing the long history of the oreodont family from the evolutionary point of view1 we find a course of development which differs in several respects from that exemplified by most of the families previously considered3 7#a7 ,there was a general increase in size1 though it was far from steady1 and almost every genus had larger and smaller species1 and in some of the phyla the species were far larger than in others4 ,the members of the ,leptauchenia phylum were very small and no member of the family ever attained to more than moderate size4 7#b7 ,the upper molars early lost the fifth cusp1 and after that there was little change in the dentition1 except that in the ,merychyus and ,leptauchenia phyla the grinding teeth became hypsodont4 7#c7 ,there was great variety in the modifications of the skull1 each phylum having its own peculiarities4 ,the orbit1 which was open behind in the ,uinta ,protoreodon1 was closed in the ,white ,river and all succeeding genera4 ,in the ,merycochrus series1 the skull first enlarged1 with little change in proportions1 then elongated the facial region1 then shortened the face and so reduced the nasals as to indicate the presence of a proboscis1 culminating in the grotesque1 ape-like skull of ,pronomotherium4 ,in the ,leptauchenia phylum the skull became depressed and flattened and the face was invaded by great openings1 or vacuities2 the tympanic bull were enormously inflated and the orbits and ear-openings raised1 presumably in adaptation to an amphibious mode of life4 ,these were the extremes of change within the family2 the other phyla need not be considered4 7#d7 ,at an early stage the digits were reduced from five to four1 first in the pes and then in the manus1 and there reduction ceased2 though in ,merychyus1 especially in the upper ,miocene species1 the lateral digits were very slender and1 had this series survived1 it would probably have led to didactyl forms4 ,illustration3 ,,fig4 #bjd4--,left manus of oreodonts4 ,a1 ,merycoidodon culbertsoni1 ,white ,river4 ,b1 ,merycochrus proprius1 upper ,miocene4 ,in other respects there was very little difference in the skeletons of the various phyla and herein lies the peculiarity in the history of the family1 great variety in the form of the skull1 and1 relatively speaking1 hardly any change in the body1 limbs or feet4 ,in the horses1 rhinoceroses and titanotheres the modifications of the successive genera affected all parts of the structure1 but in the oreodonts1 except for the loss of one digit in manus and pes and variations in the length of the tail1 the skeletons of the latest genera did not differ in any important respect from those of the earliest4 ,such a combination of mutability and plasticity in the skull with extreme conservatism in the remainder of the bony structure is an exception to the usual mode of development1 though something of the same sort has already been pointed out in the case of the tapirs 7p4 #cbe7 and will recur in that of the elephants 7,chap4 ,x74 #e4 ,agriochrid4 ,agriochrids ,this family1 one of the strangest and most aberrant of ungulate groups1 was very closely allied to the oreodonts and by many authorities is included in the same family4 ,the history of the successive steps of discovery1 by which the structure of these extraordinary animals was gradually made plain1 is much the same as in the case of the even more peculiar perissodactyl family of the chalicotheres 7p4 #cef74 ,the various parts1 found scattered and at long intervals of time1 had been referred to no less than three different mammalian orders6 for1 until the discovery of chalicothere skeletons gave the clue1 no one imagined that such discordant parts could belong to the same animal4 ,illustration3 ,,fig4 #bje4--,skull of ,agriochrus latifrons1 ,white ,river4 7,after ,wortman47 ,illustration3 ,,fig4 #bjf4--;,agriochrus antiquus1 ,white ,river4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,the agriochrids had a very much shorter career than the allied family of the oreodonts1 extending only through the upper ,eocene and the ,oligocene 7,uinta to ,john ,day1 inclusive72 and only two genera of the family are yet known1 ,agriochrus of the ,john ,day and ,white ,river1 and ,protagriochrus of the ,uinta4 ,in the former the teeth were not in a continuous1 closely crowded series1 but there were open spaces behind the upper canine and first lower premolar2 the same exceptional character of the lower teeth which was found in the oreodonts was repeated in the present family1 the canine assuming the form and functions of an incisor and the first premolar those of the canine2 the upper incisors were extremely small and were shed in the adult1 just as in the true ruminants4 ,the molars had the selenodont pattern1 but the upper molars were very different in shape from those of the oreodonts1 resembling rather those of the anthracothere ,bothriodon 7see p4 #cgj74 ,another difference from the oreodont dentition was that the last lower premolar had acquired the molar form and the last upper one nearly so1 a very unusual feature among the artiodactyls4 ,the skull was almost exactly like that of the ,white ,river oreodonts1 save in a few details2 the face was somewhat longer1 the orbit was open behind and there was no glandular pit on the face in front of the eye4 ,the neck was short and the body long1 and the backbone in the region of the loins very stout1 the vertebr of this region having much resemblance to those of the great cats1 as though ,agriochrus were an agile and powerful leaper4 ,another likeness to the cats was in the very long and heavy tail1 which was much longer than in the oreodonts1 and its vertebr were hardly distinguishable from those of a ,leopard4 ,the limbs were relatively longer than those of the oreodonts and the separate bones had a suggestive likeness to those of carnivores1 and1 more specifically1 of cats4 ,the feet1 save in one particular1 were not only artiodactyl1 but also characteristically oreodont in structure and1 as in the earlier members of that family1 there were five toes in the manus and four in the pes4 ,the exception was that1 instead of narrow and slender hoofs1 the feet were armed with sharp1 though not very large claws1 which were not comparable in relative size to the great claws of the chalicotheres4 ,altogether1 a strange jumble of incongruous characters was united in this skeleton4 ,were only the skeleton known without the skull1 one would be tempted to call it that of a carnivorous artiodactyl1 but the teeth make such a suggestion absurd1 since they could have been used only for masticating a diet of soft vegetable substances4 ,no flesh-eater has1 or ever had1 teeth in the remotest degree like these1 which were of characteristically herbivorous type4 ,how such a creature lived and what were its habits1 are questions to which no satisfactory answer has been found4 ,illustration3 ,,fig4 #bjg4--,right manus of ,agriochrus latifrons1 ,white ,river4 7,after ,wortman47 ,protagriochrus of the upper ,eocene is1 unfortunately1 known only from very imperfect and fragmentary specimens1 which1 however1 are sufficient to determine some significant points4 ,these remains show that1 while the two families of the agriochrids and the oreodonts were already distinct in the ,uinta1 they were decidedly nearer together than they became in the ,oligocene4 ,in other words1 it is clear that the two groups were converging back to a common ancestry4 ,this may be discovered in the ,bridger1 but it seems more probable that these forms were immigrants4 ,another fact concerning the ,uinta genus1 which is important1 is that the upper molars possessed the fifth or unpaired cusp which also occurred in the contemporary oreodonts1 as well as in the anthracotheres and other ,old ,world families4 ,,suborder ,,tylopoda4 ,,camels ,,and ,,camel-,,like ,,animals ,existing ,tylopoda are all included in a single family1 the ,camelid1 and by several authorities no other family1 even of extinct forms1 is admitted to the suborder4 ,my own preference1 however1 is to refer the problematical little hypertragulids to this group1 as will be shown subsequently4 #f4 ,camelid4 ,camels and ,llamas ,under modern conditions1 no mammals could seem more completely foreign to ,north ,america than those of the camel family1 which1 now restricted to two well-defined genera1 inhabit central ,asia and the colder parts of ,south ,america4 ,yet1 as a matter of fact1 this family passed through nearly the whole of its development in ,north ,america and did not emigrate to the other continents before the late ,miocene or early ,pliocene1 and it is this ,north ,american origin of the family which explains its otherwise inexplicable distribution at the present time4 ,to all appearances1 the whole family had completely disappeared from this continent in the later ,pleistocene1 but in the middle and earlier portions of that epoch both true camels and large llama-like animals were very abundant on the ,great ,plains and in ,california1 while they seem to have avoided the forested regions4 ,in order to appreciate the changes through which the camels and llamas have passed1 it will be necessary to consider briefly the skeletal and dental structure which characterizes the modern genera4 ,in the true camels 7,camelus7 the first and second upper incisors have been lost1 but the third remains as a large1 sharp-pointed tooth1 as are also the upper canine and first premolar2 thus there are three pointed1 spike-like teeth in a row1 with spaces between them1 constituting with the lower canine a very effective lacerating apparatus4 ,behind the first premolar is a long gap1 the second being suppressed2 the third and fourth are grinding teeth1 but unusually small4 ,the molars are selenodont and high-crowned1 though not extremely hypsodont4 ,the lower incisors are large and shovel-shaped1 the canine large and erect and there are but two lower premolars4 ,the dental formula thus is3 i #a_/c1 c #a_/a1 p #c_/b1 m #c_/c4 ,the skull is long1 with the facial region much and abruptly narrowed1 which gives a triangular appearance to the head when seen from above2 the orbit is completely encircled with bone and the sagittal and occipital crests are very prominent4 ,the tympanic bull are large and filled with spongy bone4 ,the condyle of the lower jaw is hemispherical and not1 as it is in most ungulates1 semicylindrical1 and a curious1 hook-like angulation is on the posterior border of the bone4 ,the neck is very long1 and the vertebr have the exceptional peculiarity that the canal for the vertebral artery runs through the side of the neural arch1 instead of perforating the transverse process1 and thus is invisible externally2 the odontoid process of the axis is spout-like4 ,the legs and feet are very long2 the humerus has a double bicipital groove and the fore-arm bones are cossified1 and the ulna is so reduced that the radius carries the whole weight2 in the lower hind leg the tibia supports the weight1 and of the fibula only the lower end remains as the malleolar bone4 ,there are but two digits in each foot1 the third and fourth1 the metapodials of which have coalesced to form a cannon-bone1 which differs from that of the true ruminants1 or ,pecora1 in the curious way in which the lower ends1 separated by a -shaped notch1 diverge from each other1 and by the fact that the keels of the lower articular surfaces are confined to the posterior side1 not visible from the front4 ,the ungual phalanges are small and nodular1 and the hoofs1 which carry no part of the weight1 are hardly more than nails4 ,under the other phalanges is a broad pad of elastic tissue1 upon which the weight rests1 and the separation of the toes is very partial4 ,the peculiar external appearance of the camels is largely due to structures which leave no trace in the skeleton1 and especially to the great humps1 one or two according to the species1 which are accumulations of fat2 the ears are short and rounded and the hair is not woolly1 but almost straight4 ,the teeth and skeleton of the llamas 7,lama7 are closely similar to those of the camels1 but the absence of humps1 the long1 pointed ears1 the woolly hair and the much smaller size and lighter build give to the living animals a more marked difference of appearance from the camels than one would expect from a comparison of the skeletons alone4 ,the dental formula is3 i #a_/c1 c #a_/a1 p #b_/b1 m #c_/c4 ,the remaining upper incisor1 the third1 is recurved1 as is also the canine1 but the spike-shaped first premolar of the camels is absent and the other premolars are much smaller than in the latter4 ,in the skull the brain-case is larger1 and the sagittal and occipital crests are much less prominent4 ,the skeleton differs hardly at all from that of the camels1 except for its smaller size and more slender proportions4 ,the toes are more distinctly separated1 each having its own pad4 ,thus1 among the existing representatives of the family are two very well-defined phyla1 each characteristic of a different continent4 ,illustration3 ,,fig4 #bjh4--;,guanaco 7,lama huanacus74--,by permission of the ,new ,york ,zological ,society4 ,the ,blanco stage of the middle ,pliocene1 which has preserved but a meagre representation of the life of its time1 has yielded a number of very large1 llama-like species1 not1 however1 ancestral to the modern species1 for they had but one premolar in each jaw4 ,from the lower ,pliocene we have fuller information4 ,in the ,snake ,creek stage the separation of the two modern phyla was complete1 and there was a third one1 now extinct1 that of the browsing or 8giraffe-camels0 7,alticamelus7 7see ,fig4 #abg1 p4 #bcf71 a term which must not be taken as implying any relationship with the giraffes1 but merely a resemblance to them in proportions4 ,these browsing camels were very large animals1 but with relatively small heads and low-crowned teeth not suited for grazing2 the neck was extremely long1 made so by the great elongation of five of the vertebr 7second to sixth1 inclusive71 and the legs were also very long1 fitting their possessors to browse upon trees4 ,much of the description of the appearance and habits of the ,giraffe given by ,flower and ,lydekker would no doubt be applicable to these extinct camels4 8,to produce the extremely elongated neck the seven cervical vertebr are proportionately long1 which gives a somewhat stiff and awkward motion to the neck4444 ,the ,giraffe feeds almost exclusively on the foliage of trees 444 for browsing on which its prehensile tongue and large free lips are specially adapted40#h ,in teeth and skeleton the phyla of the true camels and of the llamas in the lower ,pliocene did not differ very strongly from the living forms2 the upper incisors were already reduced to one1 but the premolars were not so small2 the ulna and radius had coalesced and of the fibula only the lower end remained2 the cannon-bones were completely formed1 and that the pads of the feet had already been developed is shown by the phalanges1 especially the irregular1 nodular unguals4 ,the most ancient known camels of the ,old ,world are found in the ,pliocene of ,india1 and the first llamas recorded in ,south ,america are also ,pliocene4 ,since both camels and llamas existed together in ,north ,america1 it may reasonably be asked why only one phylum migrated to ,asia and only the other to ,south ,america4 ,why did not each continent receive migrants of both kinds8 ,without knowing more than we are ever likely to learn about the details of these migrations1 it will not be possible to answer these questions1 though plausible solutions of the problem suggest themselves4 ,it is to be noted1 in the first place1 that a migration from the central portion of ,north ,america to ,asia was by way of the far north and thus involved very different climatic conditions from those which must have been encountered in passing through the tropics to ,south ,america4 ,it is perfectly possible that animals which lived together in temperate ,north ,america should have had very different powers of adaptation to heat and cold respectively1 and the northern route may have been impassable to one and the southern route to the other4 ,to this it might perhaps be objected that the llamas are cold-country animals1 but this is true only of the existing species1 for fossil forms are found abundantly in the ,pleistocene of ,ecuador1 ,brazil and ,argentina4 ,another possibility is that both phyla did actually migrate to both continents and that only the camels succeeded in permanently establishing themselves in ,asia and only the llamas in ,south ,america1 though for this solution the fossils afford no evidence4 ,the camels of the upper ,miocene did not differ sufficiently from those of the lower ,pliocene to call for special notice other than to remark that the two phyla of the true camels and the llamas were hardly distinguishable and one genus 7,procamelus7 may have been ancestral to both4 ,in the middle ,miocene the browsing camels 7,alticamelus7 reached the acme of their importance and made no great progress subsequently4 ,the generalized stock1 from which the upper ,miocene and lower ,pliocene ,procamelus descended1 was represented by ,protolabis and ,miolabis1 smaller animals1 which had a full set of upper incisors and premolars and the grinding teeth were not so high-crowned4 ,in most of the species the metapodials had not fused to form cannon-bones and probably there were no pads on the feet1 though ,alticamelus1 the ,giraffe-,camel1 had already developed both cannon-bones and pads4 ,illustration3 ,,fig4 #bji4--,lower ,miocene giraffe-camel 7,oxydactylus longipes74 ,restored from a skeleton in the ,carnegie ,museum1 ,pittsburgh4 ,in the lower ,miocene the giraffe-camels were represented by the genus ,oxydactylus1 which was a considerably smaller animal than its successor ,alticamelus1 of the middle ,miocene and later formations1 and had shorter neck and legs4 ,the teeth1 though brachyodont1 were not very low-crowned4 ,there was no cannon-bone1 the two metapodials of each foot remaining separate4 ,an especially noteworthy feature in this genus is to be observed in the character of the hoofs1 which1 as the ungual phalanges demonstrate1 were narrow and pointed1 like those of antelope and deer1 and carried most of the weight4 ,the member of the grazing series 7,protomeryx7 was smaller in every way than its contemporary 7,oxydactylus7 of the browsing line and had shorter neck and legs1 though these were already long4 ,the teeth were present in undiminished number1 and the grinders1 while not properly to be called hypsodont1 showed a decided tendency to assume that character4 ,the feet were in the same stage of development as in ,oxydactylus1 that is to say1 with two free digits and pointed1 deer-like hoofs4 ,we have thus the remarkable and most significant fact that1 while the grazing and browsing camels of the lower ,miocene were already distinctly separated1 neither had yet attained to the type of foot-structure which both of them afterwards independently acquired4 ,this is a very instructive example of parallel evolution in closely related series4 ,illustration3 ,,fig4 #baj4--,skeleton of ,oxydactylus longipes4 ,lower ,miocene4 7,after ,peterson47 ,for restoration1 see ,fig4 #bji4 ,of still another phylum of the camel family1 the lower ,miocene contains the only representatives yet discovered1 the little 8gazelle-camels10 as they may be called4 ,the single known genus 7,stenomylus1 ,fig4 #aca1 p4 #bdb7 of this series was quite a small animal1 much smaller than its contemporaries of the grazing or browsing series4 ,stenomylus was an extremely slender1 cursorial creature and had a very exceptional feature in its dentition in the apparent presence of ten lower incisors1 five on each side1 the canine and first premolar having assumed the form and functions of the incisors2 the molars were low-crowned4 ,the head was rather small and rounded1 the neck long and light1 the limbs and feet elongate and excessively slender4 ,the feet had two digits each1 which were separate1 not forming a cannon-bone1 and the hoofs were narrow1 pointed and deer-like4 ,these delicate and graceful little animals had but a brief career1 which seems to have reached its close in the lower ,miocene4 ,perhaps their complete defencelessness made it impossible for them to maintain themselves against their enemies1 despite their evident capacity for swift running4 ,the camels of the upper ,oligocene 7,john ,day7 are still incompletely known1 but appear all to have belonged to the series of grazers which led up to the modern genera4 ,future discovery may bring to light in the ,john ,day earlier members of the giraffe-camel series1 of which a possible member is found in the uppermost substage of the ,white ,river1 or perhaps both phyla united in the upper ,oligocene1 a question which remains to be determined4 ,at all events1 in the middle substage of the ,white ,river1 or lower ,oligocene1 there is no evidence of more than a single phylum1 from which the others were almost certainly derived1 branching off from the main stem at different levels4 ,first was given off the branch of the giraffe-camels1 then 7or perhaps even earlier7 that of the little gazelle-camels1 and1 finally1 the main stem bifurcated into the two phyla of the llamas and the true camels4 ,the point of origin of the gazelle-camels is still uncertain4 ,illustration3 ,,fig4 #baa4--,the ,white ,river camel 7,pobrotherium labiatum74 ,restored from a skeleton in the museum of ,princeton ,university4 ,the typical ,white ,river genus 7,pobrotherium7 included a series of species which increased in size from the earlier to the later portions of the stage1 but showed no such structural changes as to call for special notice4 ,the larger of these species was somewhat taller than a sheep1 but of much lighter proportions1 with small1 pointed head1 long neck and body and long1 very slender limbs and feet4 ,the teeth were present in undiminished number1 #dd in all2 the lower incisors were small1 simple1 nearly erect and chisel-shaped1 very different from the large1 procumbent and shovel-like teeth of the modern genera1 and the trenchant canines were much smaller than in the latter4 ,the first premolar had an isolated position1 the second and third were trenchant and much extended antero-posteriorly1 quite as in many other groups of primitive artiodactyls4 ,the molars1 which were typically selenodont1 were low-crowned in the upper jaw1 but in the lower showed an incipient tendency to hypsodontism4 ,the skull1 by its shape and the characteristic narrowing of the face1 immediately suggests the modern type1 but differed in many details of structure1 the most obvious of which were the incompletely closed orbits1 the shallow and slender jaws1 and the very large1 hook-like process from the angle of the lower jaw1 which1 in greatly reduced form1 is present in both of the ,recent genera4 ,the neck was relatively long1 though by no means so long proportionately as it subsequently became1 and the vertebr had already acquired the peculiarity found in all the succeeding camels1 of the exceptional position of the canal for the vertebral artery1 save in the sixth vertebra1 where it pierced the transverse process1 as in mammals generally2 the odontoid process of the axis was neither spout-like nor peg-like1 but of intermediate form1 convex below and flat above4 ,the body was long and light1 and the ribs were much more slender than in the ,recent genera4 ,the fore and hind limbs1 which were of nearly equal length1 were very slender2 the humerus had a single bicipital groove2 the fore-arm bones were fully cossified and in the lower leg only the two ends of the fibula remained4 ,the feet were already in the stage of development which persisted through the lower ,miocene in all of the phyla1 with two separate digits and nodular remnants of two others1 and deer-like hoofs4 ,it would be of interest to compare this little ,white ,river camel with its contemporary genus of horses1 ,mesohippus1 and to observe in how many respects they have followed a parallel course1 and how nearly ,pobrotherium occupied the same position with reference to the modern camels and llamas as ,mesohippus did to the ,recent horses2 but such a comparison would involve too many technicalities to be profitably undertaken here4 ,suffice it to say that in many details there was a genuine parallelism in the progress of these two widely separated families from a polydactyl ancestry towards an extreme of digital reduction1 ending in the horses in the single-toed and in the camels in the two-toed foot4 ,the members of the two series kept nearly equal pace in their slow progress1 with the camels a little in advance1 since they were the first to attain the modern state of development in the height of the teeth and the structure of the feet1 though eventually the horses surpassed them in both respects4 ,in the upper ,eocene 7,uinta stage7 there were at least two kinds of camels1 the time-relations of which to each other are not known1 that is1 whether they were contemporary or successive4 ,the best-known genus1 ,protylopus1 may perhaps not be in the direct line of camel descent1 but it so nearly represents the proper ancestral stage that1 for all practical purposes1 it will serve nearly as well4 ,it was a much smaller animal than the smallest of the ,white ,river species1 and was hardly larger than a 8jack-rabbit40 ,the teeth of each jaw were in continuous series and the canines were but slightly longer than the incisors2 the premolars had less antero-posterior extension than in ,pobrotherium1 and all the molars above and below were very low-crowned4 ,the skull was almost a miniature copy of that of ,pobrotherium1 but more primitive in a number of details1 the most important of which was that the tympanic bull were much smaller and hollow1 not filled with spongy bone4 ,the neck1 concerning which it would be very desirable to have information1 is almost the only part of the skeleton that is not known4 ,the fore limb was considerably shorter than the hind1 making the back slope downward from the rump to the shoulders2 in the fore-arm the two bones were entirely separate and in the lower leg the fibula1 though very slender1 was still complete4 ,in the manus there were four functional digits1 the laterals not very much smaller than the median pair2 but in the pes the lateral metatarsals were reduced to mere bony threads1 to which small phalanges1 in full complement1 were attached1 making tiny dew-claws4 ,with ,protylopus ends the genealogy of the camels so far as it can be definitively traced1 but in the middle of the ,bridger stage is found a genus1 ,homacodon 7family ,dichobunid71 which is a probable member of the series4 ,however1 until the connecting link can be found in the upper ,bridger1 this conclusion cannot be demonstrated and ,homacodon itself is incompletely known4 ,it was a very small animal1 even less in size than ,protylopus1 and had not yet acquired the selenodont molars4 ,these teeth were quadritubercular1 i4e4 with four principal cusps arranged1 in the upper molars1 in a square1 and with a minute cuspule between each transverse pair1 while the lower molars were narrower and had only the four principal cusps4 ,the cusps were not conical1 as they are in the pigs1 but angular and pyramidal1 the first step toward the assumption of the selenodont form4 ,the skull was not specifically cameline in appearance1 but rather indifferent1 as though almost any kind of an artiodactyl might have been derived from it4 ,the feet were decidedly more primitive than those of the ,uinta genus1 having four functional digits each1 perhaps five in the manus4 ,while it cannot be positively stated that ,homacodon was the actual ancestor of ,protylopus1 it nearly represents what we should expect that ancestor to be4 ,illustration3 ,,fig4 #bab4--;,diagram to illustrate the development of the skull and molar teeth in the camel tribe1 in ascending geological order4 ,a1 ,protylopus petersoni1 ,uinta ,eocene4 ,b1 ,pobrotherium wilsoni1 ,white ,river4 7,after ,wortman47 ,c1 ,procamelus gracilis1 upper ,miocene4 7,after ,cope47 ,d1 ,lama huanacus1 the modern ,guanaco4 ,in the lower ,eocene 7,wasatch stage7 lived a tiny creature1 ,trigonolestes 7family ,trigonolestid71 smaller even than ,homacodon of the ,bridger1 and one of the most ancient and primitive of known artiodactyls1 but1 unfortunately1 still represented only by very imperfect specimens1 so that much which it would be highly desirable to learn must await the finding of better material4 ,the upper molars were triangular and tritubercular1 i4e4 with three principal cusps arranged in a triangle1 and are hardly to be distinguished from those of other early mammalian orders4 ,from the teeth alone the artiodactyl nature of the animal would not have been suspected1 and1 in fact1 they were1 when first discovered1 referred to primitive monkeys4 ,the feet probably had five toes each1 but this is not certain1 and the femur had the third trochanter1 the only known artiodactyl of which this is true4 ,as this little ,wasatch genus is so imperfectly known1 it would be premature to claim it as the starting point of the camel family1 and yet it may very well have been so4 ,better material of this genus and the links of the chain which belong in the upper ,bridger and the ,wind ,river respectively must be recovered before this earliest portion of the family history can be written in more than tentative fashion4 ,illustration3 ,,fig4 #bac4--,right manus of camels4 ,a1 ,protylopus1 ,uinta4 ,b1 ,pobrotherium1 ,white ,river4 ,c1 ,procamelus1 upper ,miocene4 7,after ,cope47 ,d1 ,recent ,guanaco4 ,illustration3 ,,fig4 #bad4--,right pes of camels4 ,a1 ,protylopus4 ,b1 ,pobrotherium4 ,c1 ,procamelus4 7,after ,cope47 ,d1 ,guanaco4 ,the mode of evolution displayed by the camels does not differ in any significant respect from that seen in the horses4 ,there was the same increase in bodily stature and in the relative lengths of the limbs and feet1 the same kind of diminution in the number of digits from the original five1 the same reduction of the ulna and its coalescence with the radius and the loss of the fibula save for its two ends4 ,there was also a similar development of the high-crowned1 or hypsodont1 grinding teeth1 from the low-crowned1 or brachyodont1 type4 ,in still another respect there was a similarity in the mode of development of the two families1 namely1 in the way in which the several phyla of each originated4 ,for the earlier portion of their history there was in each but a single distinguishable series1 though it is very possible that fuller knowledge and more complete material would enable us to distinguish more than one4 ,this monophyletic condition continued through the ,eocene and most of the ,oligocene1 but in the upper portion of the latter and1 more markedly in the lower ,miocene1 the two families branched out1 each in its own fashion4 ,of course1 there were differences in the development of the camels and horses1 some conditioned by the fundamental distinction between artiodactyl and perissodactyl1 such as the didactyl foot as the possible minimum and the formation of cannon-bones in the camels4 ,other differences are characteristic of the latter family1 such as the great elongation of the neck and the peculiar structure of its vertebr1 the formation of pads on the feet and concomitant reduction of the hoofs4 ,in a general way1 the two families kept quite an even pace in their advance from the more primitive to the more specialized condition and1 though the camels were the first to acquire certain modifications1 the horses ultimately surpassed them4 ,even more close was the parallelism in evolution between the camels and the true ruminants 7suborder ,pecora71 and this case is of particular importance as clearly demonstrating the development1 in two independent but related lines1 of similar structures not derived from a common ancestry4 ,this comparison must naturally await the description of the ,pecora4 #g4 ,hypertragulid4 ,hypertragulids ,this was a very peculiar family1 of exclusively ,north ,american distribution and of doubtful systematic position1 the known history of which extended from the upper ,eocene into the lowest ,miocene and then abruptly terminated4 ,none of its members attained to considerable size1 the largest hardly surpassing a sheep1 and some were extremely small4 ,in view of its comparatively brief career1 this family was surprisingly ramified1 and no less than four phyla may be distinguished within its limits4 ,illustration3 ,,fig4 #bae4--,syndyoceras cooki1 lower ,miocene4 ,restored from a skeleton in the museum of the ,university of ,nebraska4 ,one of the phyla which persisted into the lower ,miocene was there represented by a most fantastic creature 7,syndyoceras7 with four horn-like outgrowths from the skull1 one pair arising from the anterior part of the face and curving outward away from each other1 and the hinder pair1 which were placed over the eyes1 curved toward each other at the tips and were shaped much like a cow's horns in miniature4 ,the shape of these bony protuberances makes it unlikely that they were sheathed in horn and probably they were merely covered with skin like the horns of the giraffes4 ,this description applies only to the skull of the male2 that of the female is not yet known1 but there is good reason to believe that in that sex the horns were much smaller or wanting1 as in nearly all existing deer4 ,the skull was long1 narrow and low2 the orbits were small1 completely enclosed in bone and unusually prominent2 the nasal bones were exceedingly short1 as though indicating the existence of a proboscis1 but this can hardly have been the case1 for the nasal opening was divided into anterior and posterior portions by the bony bridge which united the bases of the forward pair of horns4 ,in no other known mammal does such a division of the nasal opening occur4 ,the upper incisors had all disappeared1 but there was a small upper canine tusk and another formed by the first lower premolar1 while the real lower canine had gone over to the incisor series4 ,this exceptional arrangement is a point of resemblance to the oreodonts 7see p4 #cgb74 ,the grinding teeth were brachyodont4 ,the fore limb is not known1 but the hind limb has been completely recovered2 it was stout and not very long in proportion to the length of the head4 ,the fibula was completely reduced1 only the ends remaining1 and the pes was didactyl1 the two metatarsals uniting in a cannon-bone2 the hoofs were like those of deer and antelopes4 ,illustration3 ,,fig4 #baf4--,protoceras celer1 upper ,white ,river2 males on the right and left1 female in the middle4 ,restored from skeletons in the ,american ,museum and ,princeton ,university4 ,no representative of this series has yet been found in the upper ,oligocene2 and it is not yet possible to say whether their absence from the ,john ,day beds1 as in several other cases already referred to1 was due to an actual geographical difference in contemporary faunas1 or whether it is merely one of the accidents of preservation and collecting4 ,in the upper ,white ,river1 however1 was another most curious animal 7,protoceras71 a forerunner1 if not a direct ancestor1 of ,syndyoceras4 ,the exact relationship between the two forms can hardly be determined1 until the genera1 one or more1 which once connected them shall have been recovered1 though it is obvious that they belonged to the same series4 ,protoceras was a smaller animal and1 if anything1 an even more bizarre-looking object1 for the anterior protuberances were broad1 prominent and everted plates of bone1 not even suggesting horns in their form1 and the posterior pair were short and club-shaped2 in the female neither pair was more than indicated4 ,the dentition was very similar to that of ,syndyoceras1 except that the upper tusk was considerably larger and scimitar-shaped2 the female had no tusks4 ,in the fore-arm the two bones were just beginning to coalesce1 but in the lower leg the fibula was completely reduced4 ,the manus had four complete and functional digits1 the laterals not very much shorter and thinner than the median pair2 but the pes was already didactyl1 though the metatarsals were separate1 not fused into a cannon-bone2 two long and pointed splints were the vestigial remnants of the second and fifth digits4 ,illustration3 ,,fig4 #bag4--,protoceras celer1 skull of male4 7,after ,osborn and ,wortman47 ,it is not yet possible to trace this phylum below the level of the uppermost ,white ,river beds1 yet that will very probably be accomplished by future exploration4 ,the second phylum of the family was represented in the lowest ,miocene by ,hypertragulus1 a genus of much smaller animals than those of the preceding series1 which went back to ,white ,river times without essential change1 and was abundant in the ,john ,day stage4 ,despite this fact1 the structure of the genus is still incompletely known and much remains to be learned1 but enough has already been ascertained to justify the association of this phylum with the ,protoceras-,syndyoceras series in one family as reasonable4 ,the number of upper incisors in ,hypertragulus has not been ascertained1 but the canines were enlarged and tusk-like1 the lower one not having gone over to the incisors1 as it had in the preceding group4 ,the skull had much resemblance to that of the contemporary camels1 the sudden narrowing of the facial region giving it a very llama-like appearance2 the orbit was open and on the face in front of it was a conspicuous vacuity4 ,the ulna and radius were cossified and there were four digits in the manus1 two in the pes1 but no cannon-bone was formed4 ,illustration3 ,,fig4 #bah4--,skull of ,leptomeryx evansi1 ,white ,river4 7,after ,matthew47 ,the third phylum1 that of ,leptomeryx1 had about the same range in time as the preceding one1 though it has not yet been found in the ,john ,day1 and the genus is assuredly known only from the ,white ,river beds1 in which it is not uncommon4 ,leptomeryx comprised a number of species1 all very small animals1 and none larger than a jack-rabbit4 7,see ,fig4 #bgg1 p4 #efc47 ,in size1 proportions and appearance1 these dainty little creatures must have been very like the existing chevrotains or 8mouse-deer0 of ,asia and the ,malay islands1 and by many writers they have been classed in the same suborder1 the ,tragulina4 ,the upper incisors had been suppressed and the upper canine reduced to very small size1 while the lower canine had become functionally one of the incisors4 ,the skull had a very long and slender facial region1 but had a less llama-like appearance than in ,hypertragulus4 ,the neck was short and the fore limbs much shorter than the hind1 so that the back sloped downward from the rump to the shoulders1 as in the chevrotains4 ,there was a remarkable1 indeed quite unparalleled1 difference between the fore and hind limbs and feet1 the hinder extremity being not only much longer1 but also much more specialized1 while the anterior one retained in very large degree its primitive characteristics4 ,thus1 in the fore-arm the ulna was complete and separate from the radius1 but in the lower leg the fibula was reduced to its minimum4 ,in the manus there were four entire and functional digits1 in the pes only two1 which were joined in a cannon-bone4 ,finally1 there was a fourth phylum1 that of ,hypisodus1 which was confined to the ,white ,river stage and is still incompletely known4 ,this was a tiny creature1 much smaller than any of the preceding ones1 and is the only known ,white ,river ungulate with fully hypsodont grinding teeth4 ,another very exceptional peculiarity of its dentition was that in the lower jaw it had ten incisor-like teeth2 not only the canine1 but the first premolar as well1 had assumed the character of the incisors4 ,this same peculiarity is found in the lower ,miocene gazelle-camel1 ,stenomylus 7see p4 #cid71 but in no other mammal4 ,a considerable assemblage of genera belonging to this family occurs in the upper ,eocene1 but the material yet obtained is too fragmentary to permit the assignment of these forms to the different phyla1 though it is very probable that among them are to be found ancestors of all the ,white ,river and subsequent genera4 ,while there is little difference of opinion as to the propriety of including in the family ,hypertragulid the four phyla described in the foregoing pages1 the systematic position and the relationships of that family as a whole are matters of debate and likely long to remain so4 ,dr4 ,matthew refers the entire group to the suborder ,tragulina and regards ,leptomeryx as being closely related to the direct ancestry of the ,american deer1 a view which is accepted by ,professor ,osborn1 but in which ,i am unable to concur4 ,my own belief is that the family was an early offshoot from the cameline stock and therefore referable to the ,tylopoda1 in which suborder they are here included4 ,it would be out of place to enter upon a discussion of this perplexing problem1 which can hardly receive a definitive solution until the artiodactyls of the ,uinta stage are thoroughly understood4 ,as in so many other series1 the key of the mystery lies hidden in the ,uinta fauna1 which is still so inadequately known4 ,,suborder ,,pecora4 ,,true ,,ruminants ,this is the most advanced1 specialized and diversified group of the artiodactyls1 though the ruminating habit is shared by both ,tylopoda and ,tragulina4 ,in this multitude of forms1 giraffes1 deer1 antelopes1 sheep1 goats1 oxen1 buffaloes1 bisons1 etc41 it is difficult to find a clue to a natural arrangement or classification4 ,as a whole1 the suborder is a well-defined group1 and many structural characters1 not all of which is it needful to enumerate here1 are common to all of its members4 ,the upper incisors are invariably absent1 and1 save in a few of the deer1 the upper canine also1 while the lower canine has become incisiform2 the premolars are always three in number in each jaw and the molar-pattern is selenodont throughout4 ,the odontoid process of the axis is spout-shaped4 ,except in a few deer1 the ,pecora all have bony outgrowths of the skull in the form of antlers or horns1 at least in the males1 many females being hornless4 ,the ulna is cossified with the radius and the fibula is lost1 except the lower end1 which is a separate malleolar bone4 ,there is always1 in both fore and hind feet1 a cannon-bone1 the lower ends of which are parallel1 not divergent1 as they are in the ,tylopoda1 and each articular surface is encircled all around by a prominent median keel1 as in the horses1 which in the other suborders1 as in mammals generally1 is confined to the posterior side and not visible from the front4 7,cf4 ,figs4 #bbj and #bad1 p4 #dja47 ,in no existing member of the ,pecora are there complete lateral digits1 and in several modern genera they have been completely suppressed2 but in most there is1 behind the functional pair of digits1 a pair of 8dew-claws10 the bones of which are more or less completely reduced1 often to mere nodules4 ,the stomach1 which in the ,tylopoda and ,tragulina is three-chambered1 is in the ,pecora divided into four distinct parts4 ,illustration3 ,,fig4 #bai4--,left manus of ,patagonian ,deer 7,hippocamelus bisulcus74 ,s41 scaphoid4 ,l41 lunar4 ,py41 pyramidal4 ,td41 ,m41 cossified trapezoid and magnum4 ,un41 unciform4 ,mc4 ,,ii and ,v1 rudimentary second and fifth metacarpals4 ,mc4 ,,iii and ,,iv1 cannon-bone4 ,ph4 #a1 #b1 first and second phalanges4 ,ung41 ungual phalanx4 ,illustration3 ,,fig4 #bbj4--,left pes of ,patagonian ,deer4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 ,cb41 cossified navicular and cuboid4 ,mt4 ,,iii1 ,,iv1 cannon-bone4 ,other letters as in ,fig4 #bai4 ,as already intimated1 the subdivision of the ,pecora into smaller groups is far from easy4 8,the great difficulty which all zologists have felt in subdividing them into natural minor groups arises from the fact that the changes in different organs 7feet1 skull1 frontal appendages1 teeth1 cutaneous glands1 etc47 have proceeded with such apparent irregularity and absence of correlation that the different modifications of these parts are most variously combined in different members of the group40#i ,two main sections of the suborder are1 however1 sufficiently well defined1 7#a7 the ,cervicornia and 7#b7 the ,cavicornia4 ,,section ,,cervicornia4 ,,deer ,,and ,,giraffes ,this section includes two families1 the giraffes and the deer4 ,inasmuch as the former have not now and never did have any representatives in the western hemisphere1 for the purposes of this book the section becomes identical with the deer family4 #h4 ,cervid4 ,deer ,in most of the deer now existing the male has antlers4 ,the antler is a bony outgrowth from the frontal bone of the skull and is annually shed and replaced1 increasing1 as a rule1 in size and in the number of branches with each renewal4 ,during the period of growth the antler is richly supplied with blood-vessels and covered with skin and is then said to be 8in the velvet10 which dries and peels off when growth is complete2 after the rutting season a layer of bone at the base of the antler is resorbed1 loosening the antler1 which is then shed4 ,there is1 however1 a permanent1 cylindrical process1 of greater or less length1 from each frontal1 the 8pedicle10 from which the antler is annually reproduced1 and around the base of the antler and shed with it is a roughened ring1 the 8burr40 ,among the different genera of deer there is great variety in the form and size of the antler1 from a single spike to the immense and complicated appendages of the ,wapiti 7,cervus canadensis74 ,as a rule1 the 8beam0 or main stem of the antler and its branches or 8tines0 are cylindrical and tapering2 but in some cases1 as in the ,moose 7,alce7 and the ,fallow ,deer 7,dama71 the antler is very broad and flat and is then said to be 8palmated40 ,except in the ,reindeer and ,caribou 7,rangifer7 the female is without antlers4 ,in the skeleton there is little difference between the deer and the ,cavicornia1 but there are some differences in the teeth4 ,in the males of those deer which have no antlers1 such as the ,musk-,deer 7,moschus moschiferus7 and the ,chinese ,water-,deer 7,hydropotes inermis71 as well as in certain forms with very small antlers1 like the muntjacs of ,asia 7,cervulus and ,elaphodus71 the upper canine is a long1 thin1 recurved and sabre-like tusk1 a very effective weapon4 ,speaking of the ,indian ,muntjac or 8,barking ,deer0 7,cervulus muntjac71 ,flower and ,lydekker say1 8,when attacked by dogs the males use their sharp canine teeth with great vigour1 inflicting upon their opponents deep and even dangerous wounds40 ,in other forms of deer the upper canines are small or absent4 ,the grinding teeth are brachyodont1 but in the existing genera they have higher crowns than in the ,tertiary progenitors of the family1 and in the ,axis and ,hog ,deer of ,india 7,axis axis and ,a4 porcinus7 the molars are quite hypsodont4 ,as was shown in ,chapter ,v1 the existing deer of ,north ,america are of two kinds3 7#a7 the northern1 which are plainly of ,old ,world origin and so closely similar to ,old ,world species that many naturalists deny the necessity of making distinct species for the ,american forms4 ,the best known of these are the ,wapiti 7,cervus canadensis71 the ,caribou 7,rangifer caribou7 and the ,moose 7,alce americanus74 7#b7 ,the southern deer1 of which the common ,virginia ,deer 7,odocoileus virginianus7 is a familiar example1 though overlapping in their range that of the northern genera1 are peculiar to the ,americas1 and1 though not exactly autochthonous1 they must have had a long ,american ancestry4 ,in the ,pleistocene we find the same genera and mostly the same species1 their distribution over the continent shifting in accordance with the many climatic changes of that epoch4 ,there was1 however1 at least one ,pleistocene genus 7,cervalces7 different from any now living and different from any known in the eastern hemisphere4 ,the most complete specimen of this animal is a skeleton in the museum of ,princeton ,university1 found beneath a bog in northern ,new ,jersey1 though other bones1 collected in ,kentucky and elsewhere1 are very probably referable to it4 ,cervalces was very nearly related to the ,moose1 the neck1 body1 limbs and feet being almost identical in the two genera1 but the skull and antlers were notably different2 the nasal bones were not nearly so much shortened as in the ,moose1 indicating that the proboscis-like snout was not so large or inflated as in the latter4 ,the antlers were quite unique2 though in general like those of the ,moose1 they were much less palmated and they had1 in addition1 a great trumpet-like plate of bone on the lower side of each antler 7see ,fig4 #aag1 p4 #bji71 such as occurs in no other known member of the family4 ,although ,cervalces has not been found in the ,old ,world1 it was almost certainly an immigrant from eastern ,asia4 ,the ,moose1 ,caribou and ,wapiti were unquestionably immigrants and came in not earlier than the ,pleistocene4 ,nothing is known in the ,pliocene or more ancient ,tertiary epochs of ,north ,america which could be twisted into forms ancestral to these typically ,old ,world genera4 ,with the southern deer 7,odocoileus1 etc47 the matter stands differently1 for these have a probable ,american ancestry extending back to the lower ,miocene and possibly much farther4 ,on the other hand1 it is not altogether certain that these may not have been ,pliocene immigrants1 for their genealogy is still in an extremely fragmentary and unsatisfactory condition4 ,the ,north ,american genus1 ,odocoileus1 extended back to the ,pliocene with very little change4 ,the annoying1 unrecorded gap of the upper ,pliocene and the meagre representation of the middle ,pliocene mammals given by the ,blanco leave us without information regarding the deer of that time4 ,in the lower ,pliocene and through the whole ,miocene we meet with frequent remains of a genus 7,blastomeryx7 which was quite probably the ancestor of the ,american types of deer4 ,it was considerably smaller than any of the existing ,north ,american species and had no antlers1 but possessed the sabre-like1 upper canine tusks1 which characterize the muntjacs and hornless deer of ,asia4 ,the limb-bones had already attained nearly their present state of development1 as regards the reduction of ulna and radius1 formation of cannon-bones1 etc4 ,blastomeryx probably entered ,north ,america in the lower ,miocene1 but1 as was mentioned previously 7p4 #dji71 ,dr4 ,matthew and ,professor ,osborn regard the genus as autochthonous and descended from the ,hypertragulid4 ,illustration3 ,,fig4 #bba4--,lower ,miocene hornless deer 7,blastomeryx advena74 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,in the middle ,miocene ,blastomeryx gave rise to an aberrant genus 7,merycodus7 which has been made the type of a distinct family 7,merycodontid1 see table1 p4 #cfb71 but this is perhaps unnecessary4 ,merycodus had deer-like antlers1 but completely hypsodont teeth such as no known member of the ,cervid possesses4 ,the middle ,miocene species 7,m4 osborni7 was a little creature1 not more than eighteen or twenty inches high at the shoulder1 and had a branched antler of three tines1 which was considerably longer than the skull1 while in the species of the upper ,miocene 7,m4 furcatus7 the antler was shorter and simply forked4 ,from the number of specimens of these animals found in which the burr is incomplete or absent1 it may be inferred that the antler was not always deciduous4 ,the legs were long and very slender1 and apparently there was no trace of the lateral digits1 even in the fore foot4 ,these peculiar hypsodont deer persisted even in the older ,pleistocene4 ,illustration3 ,,fig4 #bbb4--,miocene deer-antelopes 7,merycodus osborni1 middle ,miocene1 and ,m4 furcatus1 upper ,miocene74 ,restored from specimens in the ,american ,museum4 ,deer are the only members of the ,pecora which inhabit ,south ,america1 where there are several genera of them1 all much more nearly allied to ,north ,american than to ,old ,world forms4 ,no record of the presence of the family in the southern continent has been found in beds older than the ,pleistocene1 but in view of the degree of specialization which they have there undergone1 it is probable that the immigration took place in the ,pliocene4 ,,section ,,cavicornia4 ,,hollow-,,horned ,,ruminants ,in the animals of this second and far larger section of the ,pecora there are bony outgrowths of the skull1 from the frontal bones1 outgrowths which are permanent and non-deciduous2 these are the horn-cores1 which are tapering and unbranched4 ,the horn-core is1 in turn1 covered with a sheath of horn1 likewise unbranched and permanent1 but growing from year to year until the maximum size is attained1 a process which is familiarly illustrated in the growth of a calf4 ,among ,recent ,cavicornia there is but one exception to the rule that the horny sheath is non-deciduous and unbranched and that one is the ,prong ,buck 7,antilocapra americana74 ,in the ,cavicornia it is the very general rule that both sexes are horned1 though the females commonly have smaller horns and in several genera of antelopes the does are hornless4 ,there is almost as great variety in the shape and size of the horn as of the antler2 we find small1 medium-sized and enormously large horns1 which may be straight1 simply curved1 complexly curved1 spiral1 lyrate or twisted4 ,the antelopes have many types of horns1 as have the sheep and goats1 the oxen1 buffaloes and bisons2 but only a few of them are exemplified in the western hemisphere1 which now1 as in the preceding geological periods1 is singularly poor in representatives of the ,pecora4 #i1 #aj4 ,antilopid and ,antilocaprid4 ,antelopes ,two very different kinds of antelopes are found in ,north ,america at the present time2 one of them1 the erroneously named ,rocky ,mountain ,goat 7,oreamnos montanus71 is evidently a late immigrant from the ,old ,world1 and fossil remains of it have been found in the ,pleistocene cave-deposits of ,california4 ,this animal is a member of the true antelope family 7,antilopid7 and belongs to the chamois group of mountain-antelopes2 it has no near relatives among other ,american mammals1 living or extinct4 ,the ,prong ,buck1 or ,prong-horned ,antelope 7,antilocapra americana71 occupies a very isolated position1 so much so that a distinct family1 the ,antilocaprid1 has been created for its reception4 ,it differs from all other ,cavicornia in having a branched horn1 though the bony core is simple1 and in annually shedding and renewing the horny sheath2 the horn is directly over the eye2 there are no dew-claws and all traces of the bones of the lateral digits have completely disappeared4 ,the grinding teeth are thoroughly hypsodont4 ,the genus occurred in the older ,pleistocene1 where it was associated with the last of the deer-antelope1 or ,merycodus series 7,capromeryx71 and which1 so far as it is known1 would seem to connect the two families1 though this is doubtful4 ,a middle ,miocene genus 7,dromomeryx ,fig4 #abh1 p4 #bcg7 would be a more probable ancestor of the ,prong ,buck1 if it were not for the long1 unfilled gap of the upper ,miocene and the whole ,pliocene4 ,dromomeryx had erect horn-cores placed directly above the eyes as in the modern genus1 but low-crowned grinding teeth2 it was the most ancient ,american cavicorn yet known4 ,it remains to be determined by future exploration1 whether this middle ,miocene genus was actually the ancestor of ,antilocapra1 or merely an anticipation of it4 ,in the lower ,pliocene have been found the remains1 very incomplete1 of several antelopes1 which appear to have been immigrants from the ,old ,world1 but are too imperfectly known for any definitive reference4 ,one resembles the flat-horned1 or goat-horned1 antelopes of the ,european ,miocene and ,pliocene4 ,others had spirally twisted horns like those of the ,recent strepsicerine1 or twisted-horn antelopes of ,africa and ,asia1 but may1 nevertheless1 be referable to the ,antilocaprid4 ,antelopes even penetrated to ,south ,america1 and three genera of them have been reported from the ,pleistocene of the ,brazilian caverns and the ,argentine pampas1 but they were less successful in establishing a foothold than were the deer1 and form no part of the modern ,neotropical fauna4 #aa4 ,bovid4 ,sheep1 ,bisons1 ,oxen1 etc4 ,a series of genera1 of disputed systematic position1 is represented to-day by the so-called ,musk-,ox 7,ovibos moschatus71 which is now exclusively ,north ,american1 but in the ,pleistocene ranged over northern ,asia and ,europe as far west as ,great ,britain4 ,the ,musk-,ox1 which is at present found only in the extreme north1 is a heavy1 short-legged animal1 three and a half to four feet high1 and six feet or more in length2 the body is covered with a dense coat of woolly hair overlaid by a thatch of long1 straight hair1 which gives the animal a very shaggy appearance4 ,the horns are broad at the base1 especially so in old males1 in which they meet in the middle line and cover much of the head as with a horny casque2 they curve downward and then upward and forward1 with the tips directed toward the front2 in the females and young males the horns are very much smaller4 ,this series cannot be traced back of the ,pleistocene1 in which epoch it was not only far more widely distributed1 but also very much more diversified1 no less than three extinct genera1 in addition to the existing one1 having been found in the ,north ,american ,pleistocene4 ,one of these 7,symbos71 which extended from ,alaska to ,arkansas1 had horns which were smaller and shorter than in the modern genus1 and1 even when fully developed1 did not meet in the middle line of the head4 ,the other two genera1 from ,california 7,euceratherium and ,preptoceras ,fig4 #aaf1 p4 #bjc71 are of great interest as showing affinities to the ,musk-,ox and also to sheep and to certain antelopes1 such as the ,takin 7,budorcas7 of northern ,india and ,tibet4 ,they serve to connect the musk-oxen with other ,cavicornia1 but the origin of all these animals is to be sought in ,asia4 ,in ,recent ,north ,america there are four or five species of sheep 7,ovis7 which are confined to the mountainous and broken areas of the western part of the continent and extend from ,alaska to ,mexico4 ,the 8,bighorn0 or ,rocky ,mountain ,sheep 7,ovis canadensis7 is characterized by great1 spirally coiled horns in the rams1 in the ewes the horns are very much smaller and nearly straight2 the other species differ but slightly from this type4 ,the species ,o4 canadensis has been found in the ,pleistocene1 but nothing further is known of its history4 ,evidently1 the sheep were late immigrants4 8,the geographical distribution of wild sheep is interesting4 ,the immense mountain ranges of ,central ,asia1 the ,pamir and ,thian ,shan of ,turkestan1 may be looked on as the centre of their habitat40 8,sheep are essentially inhabitants of the high mountainous parts of the world1 for dwelling among which their wonderful powers of climbing and leaping give them special advantages4 ,no species frequent by choice either level deserts1 open plains1 dense forests or swamps4 ,by far the greater number of species are inhabitants of the continent of ,asia1 one extending into ,north ,america should read1 four or five one into ,southern ,europe and one into ,north ,africa4444 ,no remains that can be with certainty referred to the genus ,ovis have been met with in the hitherto explored true ,tertiary beds1 which have yielded such abundant modifications of ,antelopes and ,deer40#aj ,the only other division of the family which is represented in ,north ,america is that of the bisons1 of which the fast vanishing remnant of a single species#aa 7,bison bison7 is all that is left of what was once an extensive and varied assemblage4 ,the bisons differ from the true oxen in the form and structure of the skull1 in the shoulder-hump1 which is produced by the very long spines of the dorsal vertebr and in consequence of which the back slopes downward from the shoulders to the croup4 ,they differ further in the character of the hair1 which is short and woolly on the body and hind quarters1 very long and shaggy on the head and neck4 ,in the ,pleistocene of ,north ,america there were at least seven recognizable species of bisons1 which ranged over the continent from ,alaska to ,florida1 though it is not probable that they were all contemporary4 ,one of the earliest and by far the largest of these was the gigantic ,b4 latifrons1 a specimen of which in the ,american ,museum of ,natural ,history measures six feet across the horns in a straight line2 this was a ,mississippi ,valley species and extended from ,ohio to the ,gulf of ,mexico and westward to ,kansas and ,texas4 ,another gigantic species 7,b4 crassicornis7 lived in ,alaska in association with a second and smaller species 7,b4 occidentalis7 which ranged as far south as ,kansas4 ,b4 occidentalis1 though smaller than the preceding species1 was larger than the existing one and was remarkable for the great size of the hump4 ,the bisons were migrants from the ,old ,world and are the only members of the great ox-tribe that ever reached ,america4 ,at present the ,old ,world has but a single species of ,bison 7,b4 bonasus71 which has been saved from extermination only by the most rigid protection4 ,neither sheep nor bison extended their range to ,south ,america2 both are and have been essentially northern groups and seem to have been unable to cross the tropics4 99 99 99 99 99 ,from the foregoing account1 confused as it unavoidably is1 one thing at least stands out clearly1 that ,north ,america played a very insignificant rle in the evolution of the ,pecora1 and has only two peculiar groups1 the ,prong ,buck and the ,american types of deer1 and of these1 the probable ,american ancestry does not extend back of the lower ,miocene and perhaps not so far4 ,even in the ,old ,world the story1 so far as it has been deciphered1 is by no means clear and consistent1 which is no doubt due to the fact that the regions from which ,tertiary mammals have been obtained are so small in comparison with those that have yielded nothing4 ,certain broad outlines of the history may1 nevertheless1 be discerned4 ,the suborder ,pecora at an early date became divided into the two great branches of the ,cervicornia and ,cavicornia1 the former giving off the giraffe series1 which in the ,miocene and ,pliocene ramified and extended through ,asia and southern ,europe1 though now confined to ,africa4 ,in the lower ,miocene of ,europe the muntjac-like deer and the antelopes1 the first of the ,cavicornia1 were already well distinguished4 ,from the primitive antelopes arose not only the wonderful assemblage of modern antelopes1 but also the goats and sheep and the great and varied ox-tribe4 ,from the middle ,oligocene forms it may obviously be inferred that both ,cervicornia and ,cavicornia united in a single trunk1 or1 traced in the other direction1 diverged from a common stock1 to which also the suborder of the ,tragulina goes back4 ,on the other hand1 it is equally obvious that the camels and llamas have been separated from the ,pecora at least since the middle ,eocene1 and1 consequently1 the many points of agreement between the two suborders1 other than those shared with all artiodactyls1 are not due to inheritance from a common ancestry1 but have been independently acquired in the two series4 ,it will be instructive to note some of the more important of these independent similarities3 7#a7 the selenodont and more or less hypsodont character of the grinding teeth2 7#b7 the spout-shaped odontoid process of the axis2 7#c7 the great reduction of the ulna and its cossification with the radius2 7#d7 the loss of the fibula1 except for its lower end1 which persists as a separate malleolar bone2 7#e7 the formation of cannon-bones by the fusion of the third and fourth metapodials2 7#f7 the development of a complex1 many-chambered stomach4 ,other points of likeness might be cited1 but those already given will suffice to show how very important this parallel mode of evolution often proves itself to be4 ,,chapter ,x ,,history ,,of ,,the ,,proboscidea ,utterly foreign as the elephant-tribe appears to be to present-day ,north ,america1 it was a very conspicuous element in the fauna of that continent from the middle ,miocene to the end of the ,pleistocene1 and in the latter epoch it spread over ,south ,america also4 ,like so many others of the mammals which have1 from time to time1 flourished in the ,americas1 the elephants and their allies1 the mastodons1 were immigrants from the ,old ,world1 and1 until comparatively lately1 the region of their origin was a complete mystery4 ,they appeared suddenly and unheralded and at approximately the same time in ,europe and ,north ,america and nothing is known from preceding geological formations of either continent which could with any plausibility be regarded as ancestral to them4 ,the mystery was dispelled by the discoveries of ,dr4 ,c4 ,w4 ,andrews in ,egypt1 which demonstrated that these strange and huge beasts had originated in ,africa and had migrated thence through ,asia to ,europe1 on the one side1 and to ,north ,america on the other4 ,the proboscideans occupy a very isolated position among the hoofed mammals1 and in structure they display a curious mingling of high specialization with an extreme conservatism of primitive characters1 the specialization being exemplified in the teeth and head and the conservatism in the body and limbs1 very much as in the oreodont family of artiodactyls 7p4 #chb74 ,the most conspicuous of the external features in the order is the long trunk1 or proboscis1 which gives its name to the group1 and is a great prolongation of the nose1 with the nostrils at the end and a finger-like tip1 which can be used to pick up minute objects4 ,illustration3 ,,fig4 #bbc4--,molar of the ,african ,elephant 7,loxodonta africanus7 showing the oblique mode of wear4 ,heavy black lines indicate enamel1 enclosing areas of dentine1 cement covering the whole tooth4 ,in the true elephants the dental formula is3 i #a_/j1 c #j_/j1 p #j_/j1 m #c_/c1 #b #ad1 though this formula is misleading1 to the extent that the milk premolars1 three in number in each jaw1 take the place and perform the functions of the premolars1 thus adding #ab to the effective number of teeth4 ,the single upper incisor on each side grows into an immense tusk1 which has enamel only on the tip1 where it is speedily worn away2 the lower jaw is without incisors and there are no canines above or below4 ,the grinding teeth are very large and have a highly complex structure and a most exceptional method of eruption on coming into use4 ,they are thoroughly hypsodont and each is composed of a large number of high1 broad and thin plates of dentine covered with enamel and the spaces between the enamel ridges are filled with cement 7see ,fig4 #dg1 p4 #ig72 indeed1 the whole tooth is so thickly covered with cement that1 when unworn1 it looks like a mere lump1 with no ridges showing on the surface4 ,the teeth increase in size and in the number of component ridges from before backward1 and in the ,indian species 7,elephas maximus7 the number of ridges in the six grinding teeth1 including the milk premolars1 is3 #d1 #h1 #ab1 #ab1 #af1 #bd4 ,in the ,african ,elephant 7,loxodonta africanus7 the teeth are not so high and have fewer and thicker plates1 the formula being3 #c1 #f1 #g1 #g1 #h1 #aj4 ,the teeth do not succeed one another vertically in the normal mammalian fashion1 but come in successively from behind and the series moves forward1 so that the foremost tooth is pushed out1 when it is so worn down as to be of no further service4 ,as these teeth are very large and the jaws are relatively short1 only one tooth on each side1 above and below1 is in use at the same time1 though part of a second may also be involved4 ,the movement of the successive teeth is not directly forward1 but oblique1 an upper tooth coming forward and downward and a lower tooth forward and upward4 ,in consequence of this arrangement the teeth are abraded obliquely1 the anterior part first coming into use1 and1 by the time a tooth is fully in place1 the front portion is worn down to less than half the height of the hinder part4 ,all of these peculiarities in the dental system imply a very high degree of specialization and a notable difference from other mammals4 ,the skull is equally specialized1 as is indeed required by the character of the teeth and the development of the long and heavy proboscis4 ,the premaxill are converted into sheaths for the great tusks2 the nasals are extremely abbreviated and the anterior nasal opening is shifted to the top1 directly above the posterior opening1 so that the nasal canal passes vertically downward through the skull4 ,all of the bones forming the cranium are enormously thickened and at the same time lightened by the formation of an extensive system of communicating sinuses1 and thus the brain-chamber is1 as it were1 hidden away in the middle of the huge mass of the skull4 ,this explains the difficulty of killing an elephant by shooting it in the head2 the shot must be so directed as to reach the brain1 which requires knowledge and skill4 ,the neck is short1 the body long and extremely massive1 the tail of moderate length4 ,the shoulder-blade is very large and has a prominent metacromion given off from the spine2 the hip-bones are immensely expanded in correlation with the breadth of the thorax and abdomen4 ,the limbs are long1 massive and columnar1 their upper segments1 especially the thigh1 are very long1 so that the knee-joint is brought below the body and free from it to the position of the hock-joint in the ,horse2 hence1 the hind leg appears to bend in the opposite direction from the bend in the legs of ordinary quadrupeds1 in which the true knee-joint is concealed4 ,the fore-arm bones are separate and1 for most of its length1 the ulna is far heavier than the radius1 a wide departure from the proportions usual in hoofed animals4 ,the femur has no pit in its head for the round ligament and no third trochanter2 the shaft is broad and much flattened1 having quite lost the normal cylindrical shape4 ,the bones of the lower leg are also separate1 but the fibula1 though stout1 is very much more slender than the ulna4 ,the long bones have no marrow-cavities1 but are filled with spongy bone4 ,the feet are extremely short and broad and of columnar shape1 the weight resting upon a pad of elastic tissue and the small1 nail-like hoofs are mere excrescences upon the periphery4 ,there are five digits in manus and pes1 but not all of them have hoofs2 in the ,indian and ,west ,african species the number of hoofs is five in the fore foot and four in the hind1 in the ,east ,african four and three respectively4 ,in the adult the skin is quite hairless1 though the young calf has a considerable quantity of hair4 ,illustration3 ,,fig4 #bbd4--,right manus of the ,indian ,elephant 7,e4 maximus74 ,at present1 the ,proboscidea are restricted to the warmer parts of ,asia and ,africa1 where five species1 four of them ,african1 are recognized4 ,this is a very great reduction in the number of species and in the area inhabited during the ,pleistocene epoch1 when they ranged through every continent1 except ,australia1 and were adapted to every climate from the tropics to the shores of the ,arctic ,sea4 ,four distinct species of proboscideans existed in ,pleistocene ,north ,america1 three elephants and a mastodon1 though not all in the same areas1 nor probably all at the same time1 their ranges both in time and space overlapping to a greater or less degree1 but not exactly coinciding in either respect4 ,illustration3 ,,fig4 #bbe4--,vertical section through the manus of the ,indian ,elephant4 ,u1 lower end of ulna4 ,l1 lunar4 ,m1 magnum4 ,,iii1 third metacarpal4 #a1 #b1 #c1 phalanges4 ,e1 pad of elastic tissue4 7,after ,m4 ,weber47 ,the first species was an immigrant1 the northern ,mammoth 7,elephas primigenius71 which extended over the greater part of the northern hemisphere1 both in the ,old ,world and in the ,new4 ,this is the species of which complete carcasses with hide and hair have been found in the frozen gravels of northern ,siberia1 its structure and appearance being thus almost as well known as those of any modern elephant4 ,that the ,mammoth was perfectly adapted to life in a climate of severe cold is shown not only by the contents of the stomach1 which are comminuted fragments of present-day ,siberian vegetation1 but also by the dense coat of woolly hair1 covered by long1 coarse outer hair1 which afforded full protection against the cold4 ,the tusks1 with considerable variation of form1 had a tendency to spiral curvature1 curving first downward and outward1 then upward and inward2 the grinding teeth were characterized by their relative breadth and the numerous thin enamel-ridges which traversed them4 ,the number of these ridges was very variable in different individuals1 but may be expressed for the six successive teeth as follows3 #c-d1 #f-i1 #i-ab1 #i-ae1 #ad-af1 #ah-bg4 ,the skeleton was more like that of the ,indian ,elephant than of the other species1 though with a number of small differences in the skull4 ,in size1 the ,mammoth was comparatively small1 standing about nine feet six inches at the shoulders4 ,in ,north ,america its range was from ,alaska southeastward across the continent to ,new ,england4 ,the second species1 the ,columbian ,elephant 7,e4 columbi ,fig4 #aad1 p4 #aih71 was eighteen inches or more taller than the ,mammoth and rivalled the largest existing elephants in stature2 its huge tusks curved first downward and then upward and inward1 their tips crossing when full-grown4 ,the grinding teeth had fewer and thicker enamel plates than those of the ,mammoth4 ,the range of the ,columbian ,elephant overlapped the southern border of that of the ,mammoth1 but was1 on the whole1 much more southern2 it crossed the continent from ocean to ocean and covered nearly the whole of the ,united ,states1 extending down to the southern end of the ,mexican plateau4 ,the two species were very closely related and in some cases are so intergraded that it is difficult to distinguish them2 the ,mammoth was an undoubted immigrant and the ,columbian ,elephant was probably a local ,north ,american variant of it1 adapted to a somewhat warmer climate4 ,nothing is known of the skin or hair in the latter animal1 but1 from the fact that it was not a tropical species and was exposed to very cold winters1 it may be inferred that it had a hairy covering of some sort4 ,the third species of elephant 7,e4 imperator7 was older geologically than the others1 as it was more characteristic of the lower ,pleistocene and uppermost ,pliocene2 its range coincided with the western half of the region covered by ,e4 columbi1 extending far into ,mexico1 but not occurring east of the ,mississippi ,river4 ,it was an enormous creature1 the largest of known elephants1 with an estimated height of thirteen and a half feet at the shoulder 7,osborn74 ,the grinding teeth had thicker and more crumpled enamel plates than in either of the other species4 ,illustration3 ,,fig4 #bbf4--,the ,american ,mastodon 7,mastodon americanus71 ,pleistocene4 ,restored from a skeleton in the museum of ,princeton ,university4 ,the fourth of the ,pleistocene proboscideans of ,north ,america was a member of a different and much more ancient genus1 ,mastodon1 which in the ,old ,world became extinct before the end of the ,pliocene4 ,the ,american ,mastodon 7,m4 americanus7 was thus a belated survival of an ancient type1 seemingly out of place even in the strange ,pleistocene world1 which had so many bizarre creatures4 ,the distinguishing characteristic of the genus was in the simple1 low-crowned and comparatively small grinding teeth1 which had three or four prominent transverse ridges1 covered with heavy enamel1 and1 usually1 with no cement on the crowns4 ,as these teeth were so much smaller than those of the elephants1 as many as three on each side of each jaw might be in simultaneous use4 ,in this species there was no vertical succession of teeth1 but in some of the ,tertiary mastodons such succession has been observed4 ,the long tusks were directed nearly straight forward and were almost parallel1 with but slight curvature1 the convexity downward4 ,in the males there was a short single tusk or1 less commonly1 a pair of such tusks1 in the lower jaw1 which were probably not visible externally2 these were the vanishing remnants of an earlier stage of development1 when the mastodons had a fully developed pair of lower tusks1 nearly as large as the superior pair4 ,illustration3 ,,fig4 #bbg4--,last lower molar of the ,american ,mastodon4 ,the skull1 while essentially proboscidean1 was yet much lower and flatter and less dome-like than in the elephants2 the thickening of the cranial bones was less extreme4 ,the remainder of the skeleton differed so little from that of the elephants as to require no description4 ,in size1 this species about equalled the ,mammoth1 the larger individuals measuring nine feet six inches at the shoulder4 ,remains have been found which prove that the ,american ,mastodon had a covering of long1 coarse hair1 and that it fed upon the leaves1 shoots and small branches of trees1 especially of conifers4 ,there is much reason to believe that the species outlived the elephants in this continent and persisted until after the establishment here of the ,american ,indian1 and it may well have been human agency which finally extinguished the dwindling race4 ,the range of the species nearly coincided with that of the ,columbian ,elephant1 but did not extend so far into ,mexico1 and in the central part of the continent reached much farther north1 even into ,alaska4 ,in the ,pliocene of ,texas1 ,nebraska and ,idaho lived the ,american representatives of a genus 7,stegodon7 which was a connecting link between the elephants and the mastodons1 and which was especially characteristic of the ,pliocene of ,india4 ,the tusks1 which were confined to the upper jaw1 had lost their enamel and the last molar1 above and below1 had five or six enamel ridges1 but the crowns1 which in the ,asiatic species were buried in cement1 had but a small amount of this material4 ,several species of ,mastodon occur in the same beds1 but only isolated teeth have been found4 ,the mastodons1 in a broad sense of the term1 have been divided into several genera and subgenera in accordance with different schemes2 the simplest perhaps is to group into a second genus those species which had fully developed lower tusks4 ,this four-tusked genus has received several names1 of which ,tetrabelodon is most commonly used in this country1 but the term ,gomphotherium is much older and1 according to the law of priority1 must therefore be employed4 ,the lower ,pliocene species of ,gomphotherium had a pair of large lower tusks1 of cylindrical shape1 and both upper and lower tusks had longitudinal bands of enamel1 and in order to support the weight of these great tusks the symphyseal1 or chin1 region of the lower jaw was greatly elongated2 the molars had four cross-crests4 ,illustration3 ,,fig4 #bbh4--;,head of upper ,miocene mastodon 7,gomphotherium productum7 showing the chisel-like lower tusks4 ,restored from a skull in the ,american ,museum of ,natural ,history4 ,in the upper ,miocene is found another and more primitive stage of proboscidean development4 ,in these species the grinding teeth were three-ridged2 the upper tusks were quite short and curved downward1 diverging somewhat from each other1 and they had enamel bands4 ,the lower tusks were still shorter and of depressed1 flattened and somewhat chisel-like form and so worn as to show that they were regularly employed in cropping and browsing4 ,the skull was low and broad and the symphysis of the lower jaw was greatly prolonged to carry the tusks4 ,a very important fact concerning these early mastodons is that they had the normal method of tooth-succession1 permanent premolars forming beneath 7in the lower jaw1 above in the upper7 the milk-teeth and pushing them out at maturity4 ,of the middle ,miocene proboscideans not much is known beyond the mere fact of their presence in ,north ,america at that time and indeed little of the skeleton1 other than the skull1 has yet been found in the ,american ,miocene2 but well-nigh complete skeletons have been obtained from the middle ,miocene of ,europe1 and these bring out the surprising fact that the body and limbs of these species did not differ in any noteworthy manner from those of the existing elephants2 the modern skeletal structure of these animals had been attained at a time when the dentition and skull were still in a far less advanced stage of development4 ,in size1 however1 there was a decided difference1 the species of the ,american ,miocene rarely attaining a height of six feet4 ,proboscidea have been reported from the lower ,miocene of the ,great ,plains1 but the material is insufficient for a definitive judgment4 ,there is no doubt as to their presence in ,europe at that time1 but in neither continent can the history be traced any farther and we must turn to ,africa for a backward continuation of the story4 ,in the lower ,oligocene of the ,faym1 southwest of ,cairo in ,egypt1 occurs the highly interesting genus ,palomastodon1 which was much more primitive than any of the genera described above1 though it was an unmistakable member of the order and even of the family ,elephantid4 ,the dentition was already much reduced1 giving the formula3 i #a_/a1 c #j_/j1 p #c_/b1 m #c_/c4 ,the upper tusks were short1 compressed1 directed downward1 and slightly divergent1 and had a broad band of enamel on the outer side2 the lower tusks were still shorter and procumbent1 pointing straight forward1 and were covered with enamel1 which was very thick on the lower side and thin or wanting on the upper4 ,all of the grinding teeth were in place and function at the same time1 which was not true of any of the genera previously considered1 and each of the premolars had its predecessor in the milk-series1 which it succeeded and displaced in the normal vertical manner4 ,the premolars were smaller and simpler than the molars1 which were made up of three pairs of conical tubercles arranged to form a three-crested crown4 ,the skull1 as compared with that of the elephants1 was long and narrow1 the premaxillaries extending into a long snout2 the nasals were shortened1 though not so much as in the succeeding genera1 and there was probably rather a long and flexible snout than a true proboscis4 ,the skull had a long and well-defined sagittal crest1 which none of the later genera had1 and the development of sinuses in the cranial bones1 though considerable1 was much less than in the elephants4 ,the occiput was relatively high and the thickened parietals did not tower above it to any such degree as they do in the elephants4 ,the symphysis of the lower jaw was greatly prolonged1 extending out beyond the ends of the upper tusks1 and this implies that the lower lip had a corresponding prolongation4 ,the skeleton is still incompletely known1 though it may be said that the neck was probably longer than in the subsequent genera of the family4 ,the limb-bones were already proboscidean in character1 differing only in details from those of the more typical members of the order1 but the animal was more lightly built and had less massive limbs4 ,the presence of the third trochanter on the femur1 which is lacking in all of the succeeding forms1 is an interesting approximation to other and still more primitive groups of ungulates4 ,the several species of ,palomastodon represent a considerable range in size1 from animals which were not much larger than a tapir to those which equalled a half-grown ,indian ,elephant4 ,it is possible to take another and very long step back from ,palomastodon1 so long1 indeed1 as to make it apparent that one or more links in the chain are still missing4 ,the genus ,mritherium is found together with ,palomastodon in the lower ,oligocene1 but also occurs separately in the upper ,eocene4 ,it seems likely that it is a persistent middle ,eocene type and that the known species of it were somewhat aside from the main line of descent1 but that it very closely represents1 nevertheless1 a very early stage in the elephant genealogy4 ,these known species were quite small animals1 about the size of a tapir1 and therefore not much less than the smaller members of ,palomastodon4 ,the dental formula of ,mritherium was3 i #c_/b1 c #a_/j1 p #c_/c1 m #c_/c1 #b #cf4 ,the first or median upper incisor was a relatively small and simple tooth1 but the second was quite a large1 downwardly directed tusk1 which was much smaller and less curved than in ,palomastodon1 and was not capable of indefinite growth4 ,the third incisor and the canine were small1 spike-like teeth of no functional importance1 but their presence is significant as approximating the primitive1 unreduced dentition of the ungulates4 ,the lower incisors were nearly procumbent1 with a slight upward inclination2 the first one was long and the second a thick1 enamel-covered tusk1 with a chisel-like edge1 which was produced by wear4 ,the premolars were smaller and simpler than the molars1 which were quadritubercular1 the four conical cusps arranged so as to form two transverse crests1 giving a pattern like that of the early pigs and peccaries and of precisely the kind that might have been predicted from the teeth of ,palomastodon4 ,the skull had an utterly different appearance from that of ,palomastodon1 the difference being much greater than between the latter and the ,miocene ,gomphotherium4 ,it was long and narrow1 and1 except for the very prominent zygomatic arches1 of nearly uniform1 tubular shape1 the brain-case being of small capacity1 though1 as compared with other ,eocene mammals1 the brain was proportionately large4 8,it is possible that the early tendency toward a considerable cerebral development shown in these primitive ,proboscidea is one of the causes why the group has survived and flourished through so long a period0 7,andrews74 ,the cranium was very long and the facial region extremely short1 the premaxillaries not being prolonged into a snout1 as they were in ,palomastodon2 the occipital bones formed nearly the entire posterior surface of the cranium and even encroached slightly upon the roof4 ,there was a long1 but not very prominent1 sagittal crest1 and some of the cranial bones were much thickened2 in one species the hinder part of the cranial walls was distinctly inflated1 a beginning of the enormous thickening which has culminated in the true elephants4 ,the nasal bones were already much shortened1 though they were twice as long as those of ,palomastodon1 and the animal would appear to have had an incipient proboscis4 ,the neck was of moderate length and the body very long1 with at least twenty pairs of ribs1 and there was probably a long tail4 ,the hip-bone differed remarkably in its extreme narrowness from that of the later ,proboscidea and the limb-bones were much more slender1 though not dissimilar in shape4 ,at a very early period the order became divided into two main branches1 one of which includes all the forms so far considered1 and the other the very strange ,dinotherium4 ,the dinotheres entered ,europe together with the mastodons in the lower ,miocene and continued into the ,pliocene without much change and then died out1 leaving no descendants4 ,they never invaded ,north ,america1 probably because they were of more or less aquatic habit1 like the hippopotamuses1 and therefore less likely to find suitable conditions in the narrow and unstable land-bridges which connected the ,old ,world with the ,new1 than were animals of purely terrestrial habitat4 ,the dinotheres were of huge size1 equalling the larger elephants in this respect and closely resembling them in the skeleton of the body and limbs4 ,as usual in this order1 the generic peculiarities were to be found in the teeth and skull4 ,there were no superior tusks1 all the upper incisors and canines being lost1 but there was a pair of large lower tusks1 which were directed downward1 with a strong backward curvature4 ,the dental formula then was3 i #j_/a1 c #j_/j1 p #b_/b1 m #c_/c1 #b #bb4 ,the grinding teeth were relatively quite small and had1 except the first molar1 two transverse crests1 giving a pattern singularly like that seen in the tapirs4 ,the skull was remarkably long1 low and flat1 and no doubt these animals had a proboscis of some sort4 ,that the dinotheres were derived from the same ancestral stock as the mastodons and elephants is perfectly obvious and is not questioned by any one1 but it is not yet possible to trace the connection4 ,the proboscideans were late immigrants into ,south ,america1 being known there only in the ,pleistocene and late ,pliocene times1 and only the mastodons entered the southern continent1 where they gave rise to several peculiar local species in ,argentina1 ,bolivia1 ,chili and ,brazil2 one of these 7,mastodon andium7 had a deposit of cement on the crowns of the grinding teeth4 ,why the elephants1 which extended to the northern border of the ,neotropical region1 should have failed to reach ,south ,america and maintain themselves there1 is but one of many similar questions to which no assured answer can be given4 ,the evolution of the ,proboscidea was1 in a certain sense1 very similar to that of the oreodont family 7p4 #cha7 among the ,artiodactyla1 in that the developmental changes affected chiefly the dentition and the skull1 the skeleton of the body and limbs having very early acquired a character which was afterward but little modified4 ,were the skull and teeth of the lower ,miocene ,gomphotherium not known1 we should hardly hesitate to refer the skeleton to the genus ,elephas1 and even in the ,oligocene ,palomastodon all the bones of the skeleton1 other than the skull1 were characteristically and unmistakably proboscidean4 ,on the other hand1 the transformations of the teeth and skull were very profound and far-reaching1 very much more so than those which took place in the oreodonts4 ,illustration3 ,,fig4 #bbi4--;,evolution of the ,proboscidea3 on the right1 a series of skulls2 on the left1 last lower molar4 7,after ,lull1 modified by ,sinclair47 ,n4,b4 ,tetrabelodon should read ,gomphotherium4 ,in the dentition we may consider separately the development of the tusks and of the grinding teeth4 ,the first step in the known series1 as exemplified by ,mritherium1 was the enlargement of the second incisor in each jaw to form a tusk which1 though actually quite long1 was very small when judged by the proboscidean standard4 ,the upper tusk was directed vertically downward and the lower one was procumbent1 pointing almost directly forward2 the third incisor and the canine were small and in the lower jaw already lost4 ,in the next known stage1 ,palomastodon1 all of the anterior teeth1 except the tusks1 had been suppressed2 the upper tusks were longer and more curved and of an oval cross-section2 they extended less directly downward and more forward1 while the enamel was restricted to the outer side of the tusk2 the lower tusks were more fully procumbent than in the preceding genus4 ,the third stage1 that of the lower ,miocene ,gomphotherium1 showed the upper tusks greatly elongated and directed more forward than downward1 while the lower tusks were but little larger than before4 ,from the middle ,miocene two phyla may be distinguished by the tusks alone2 in one1 which was not destined to long life1 the lower pair increased greatly both in length and in diameter1 while in the other series they rapidly diminished and eventually disappeared4 ,even in the ,pleistocene1 however1 the ,american ,mastodon had remnants of these tusks in the males4 ,in the later mastodons1 the stegodonts1 and true elephants1 the upper tusks1 which alone remained1 lost the enamel bands and attained enormous proportions1 differing in the various genera and species in the extent and direction of curvature4 ,an aberrant mode of tusk development was to be seen in the dinotheres1 in which the upper pair was suppressed and the lower pair enlarged and so curved that the points were directed backward4 ,the grinding teeth underwent much more radical and striking changes4 ,at first 7,mritherium7 they were small1 very low-crowned and of simple pig-like or quadritubercular pattern1 making two interrupted cross-crests2 all were in use simultaneously and the succession of milk-teeth and premolars was by vertical replacement1 as in normal mammals generally4 ,in ,palomastodon there were three pairs of tubercles on the molars and in ,gomphotherium these coalesced into ridges1 but in all the mastodons there was more or less distinctness of the conical tubercles4 ,in one or more phyla the three-ridged plan persisted for a long time1 one such phylum terminating in the ,pleistocene ,mastodon americanus4 ,in the other series the number of ridges increased1 first to four1 then to five1 six and more 7,stegodon72 the crowns of the teeth became much larger and higher1 and the ridges1 as their number increased1 became much thinner1 and the valleys between them were filled with cement1 and finally1 in the true elephants1 with their fully hypsodont1 many-crested teeth1 were thickly covered all over with cement4 ,the vertical succession of milk-teeth and premolars was retained in ,gomphotherium1 at least in some species1 but the large molars1 which could not find room to be exposed while the premolars were in place1 came in successively from behind4 ,this horizontal mode of succession is the only one to be seen in the true elephants1 in which but one tooth1 or parts of two1 on each side of each jaw are in simultaneous use and the premolars have entirely disappeared1 but the milk-teeth are retained4 ,the changes in the skull1 which amounted to a reconstruction1 were very largely conditioned by the great increase in the length and consequent weight of the tusks1 in the size of the grinding teeth and the development of the proboscis4 ,in the earliest known type 7,mritherium7 the skull had little about it that would1 at first sight1 suggest proboscidean affinities2 it was long and narrow1 with sagittal crest and occiput of normal type1 very long cranial and very short facial region4 ,the nasal opening was directed forward and the nasal canal was relatively long and horizontal in direction1 but the nasal bones were already much shortened1 indicating that the proboscis was probably in an incipient stage4 ,the symphysis of the lower jaw was procumbent and somewhat elongated1 but to only a comparatively slight degree4 ,while the skull of ,mritherium was not obviously proboscidean1 that of its successor1 ,palomastodon1 was unmistakably so1 yet retained several primitive features1 which were lost in all of the subsequent genera1 such as the sagittal crest1 the relatively low cranium and moderate thickening of the cranial bones1 the forward direction of the nasal opening1 etc42 the symphysis of the lower jaw was very greatly prolonged4 ,as the tusks enlarged and the proboscis grew longer1 the weight of the head and its appendages necessitated a largely increased area of attachment for the neck-muscles1 and this was attained by a very great thickening of the cranial roof1 the occiput not increasing proportionately2 at the same time1 the thickened bones were honeycombed with sinuses1 so as to reduce their weight without sacrifice of strength4 ,in those species of the ,miocene ,gomphotherium which had large and heavy tusks1 this thickening was not very much less than in the true elephants4 ,the enlargement of the tusks had other consequences1 as1 for example1 in lengthening and broadening the premaxillaries and1 in the elephants1 in their downward bending1 so as to shorten still further the facial region of the skull4 ,with the development of the proboscis1 the nasal bones were reduced to a minimum and the anterior nasal opening was no longer directed forward1 but obliquely upward1 while the nasal passage lost its horizontal direction and became almost vertical4 ,the lower jaw continued to elongate the symphysis1 reaching a maximum in certain species of ,gomphotherium2 but the reverse process of shortening this anterior region of the jaw began with the reduction of the lower tusks1 and1 when these had disappeared1 nothing remained of the immensely elongated symphysis1 except the short spout of the elephant's jaw4 ,as the grinding teeth increased in height1 there was a concomitant increase in the vertical depth of the jaws for their lodgment4 ,it was an obvious advantage in the mechanical problem of supporting the enormous weight of head1 tusks and trunk to shorten the neck and thus bring the weight nearer to the point of support at the withers1 the lengthening proboscis rendering it unnecessary for the mouth to reach the ground in feeding or drinking4 ,the other parts of the skeleton underwent comparatively little change1 the degree of modification being greatest between ,mritherium and ,palomastodon4 ,throughout the series the bones of the fore-arm and lower leg remained separate1 and the feet very short and five-toed4 ,in size also the great stature and massiveness were attained early4 ,after the great migration of the ,proboscidea to the northern continents1 we find considerable differences of size between the various phyla1 though all were very large1 and even as early as the lower ,miocene of ,france1 there were species which rivalled the modern elephants in bulk4 ,it was this rapid attainment of great size and weight which appears to have been the determining factor in the conservatism of the skeleton4 ,after the skeleton had become fully adjusted to the mechanical necessities imposed by immense weight1 and that adjustment1 as we have seen1 was effected at a comparatively early period in the history of the order1 then no further modification of importance would seem to have been called for4 ,no doubt the habits and mode of life of these massive1 sedate and slow-moving animals underwent but little change from the lower ,oligocene onward4 ,there is reason to think that ,mritherium was semi-aquatic and a haunter of marshes and streams1 but1 if so1 the change to a life on dry ground was complete in the lower ,oligocene1 for the structure of ,palomastodon gives no reason for supposing that it was anything but a dweller on solid land and a denizen of forests4 ,although this book does not undertake to deal with the obscure problems connected with the marine mammals1 it may be noted in passing that one of these problems has been brought near to solution1 if not actually solved1 by the discoveries in ,egypt and that is the question concerning the origin of the ,sirenia4 ,the order includes the existing ,manatee or ,sea-,cow 7,manatus7 of the coast of ,florida1 northeastern ,south ,america and western ,africa1 and the ,dugong 7,halicore7 of the ,indian ,ocean4 ,these are mammals which are adapted to a strictly marine habitat and are incapable of existence on land1 having lost the hind limbs and converted the fore limbs into swimming paddles4 ,unlike the whales1 porpoises and other ,cetacea1 the ,sirenia are herbivorous and feed upon seaweed and eel-grass and the aquatic plants of large rivers4 ,the ,egyptian discoveries tend very strongly to the conclusion that the ,sirenia and ,proboscidea were both derived from a common stock and that the genus ,mritherium was not very far removed from the probable ancestor from which both of the orders descended4 ,,chapter ,,xi ,,history ,,of ,,the ,,amblypoda ,,and ,,condylarthra ,these are two orders of hoofed animals which long ago vanished from the earth and no member of either is known to have survived later than the ,eocene epoch2 both were of great antiquity1 dating back to the ,paleocene1 perhaps even to the ,cretaceous4 ,the last of the ,amblypoda are found in the lowest ,uinta or highest ,bridger1 but they were relatively abundant in all the more ancient beds4 ,the following table gives the more important ,american forms3 ,order ,,amblypoda4 ,short-,footed ,ungulates ,suborder ,,taligrada ,i4 ,,periptychid4 ,periptychus1 ,paleoc4 ,,ii4 ,,pantolambdid4 ,pantolambda1 ,paleoc4 ,suborder ,,pantodonta ,,iii4 ,,coryphodontid4 ,coryphodon1 ,wasatch and ,wind ,river4 ,suborder ,,dinocerata ,,iv4 ,,uintatheriid4 ,bathyopsis1 ,wind ,river4 ,elachoceras1 ,bridger4 ,uintatherium1 do4 ,eobasileus1 do4 ,as is shown in the table1 the suborder ,taligrada is entirely ,paleocene in distribution1 the ,pantodonta are lower ,eocene and the ,dinocerata chiefly middle ,eocene1 though persisting into the upper4 ,the ,dinocerata were the most striking and characteristic of ,bridger mammals1 and two or three phyla of them may be distinguished1 though for our purposes this is hardly necessary1 for these strange and bizarre creatures were all very much alike4 ,from the commonest and best-known genus 7,uintatherium7 they are called uintatheres4 ,they were large and ponderous animals1 the veritable giants of their time1 far exceeding any of their contemporaries4 ,in appearance they were among the most fantastic of the many curious beasts which the fossils have revealed4 ,the skull carried three pairs of bony protuberances1 or horn-like outgrowths2 one pair on the nasal bones suggest by their shape and character that they formed the support of dermal horns like those of the paired-horn rhinoceroses 7,diceratherium7 of the ,oligocene and lower ,miocene4 7,see p4 #bci47 ,the second pair1 which were moderately high and thick prominences1 almost cylindrical in shape and tapering but slightly to their bluntly rounded ends1 were chiefly outgrowths of the maxillaries1 or upper jaw-bones4 ,from their shape1 it is likely that these were not sheathed in horn1 but were merely covered with skin1 as were also the third pair1 which arose from the parietals4 ,these were massive1 club-shaped prominences1 eight or ten inches high and broadening to the free ends1 a shape which makes it impossible to suppose that these were true horn-cores covered with horny sheaths4 ,a high crest of bone1 representing the occipital crest1 enclosed the top and back of the cranium1 connecting the posterior pair of 8horns0 and dying away in front of them4 ,the top of the cranium had thus a deep1 basin-like character1 such as is to be found in no mammal outside of this suborder and was one of the most peculiar features of this extraordinary skull4 ,the brain-cavity was absurdly small1 the growth of the brain not having kept pace with that of the body2 the cavity is hidden away in the postero-inferior portion of the skull1 the immense thickness of the cranial walls being somewhat lightened by the formation of sinuses1 but these were much less extensive and pervasive than in other very large1 horned or tusk-bearing mammals1 such as elephants1 rhinoceroses1 etc4 ,probably1 as in the case of the titanotheres and entelodonts1 this deficiency of brain-development was at least one of the factors which led to the early extinction of the group4 ,the premaxillaries were slender and rod-like bones1 which did not meet in the middle line and carried no teeth4 ,the long and massive nasal bones and the position of the nasal opening show that these animals cannot have had a proboscis of any kind4 ,the lower jaw was remarkable for the great bony flange which1 in the males1 descended on each side from the lower border1 near the anterior end1 and served to protect the great canine tusks from fracture4 ,illustration3 ,,fig4 #bcj4--,skull of uintathere 7,uintatherium alticeps71 lower jaw supplied from another species4 ,princeton ,university ,museum4 ,for restoration1 see ,fig4 #bca1 p4 #ddg4 ,the female skull differed in two respects from that of the male3 7#a7 the horn-like protuberances were much more slender and less prominent2 7#b7 as the upper canine did not form a tusk1 the lower jaw had no flanges4 ,the skull of the artiodactyl ,protoceras 7p4 #djf7 was remarkably similar to that of the uintatheres4 ,the dental formula was3 i #j_/c1 c #a_/a1 p #c_/c1 m #c_/c1 #b #cd4 ,the upper incisors were completely lost and the lower ones had the very unusual peculiarity of being bilobate1 or having the crown separated into two well-defined cusps4 ,the upper canines in the males were very large1 relatively thin1 recurved and sabre-like tusks1 with acute points and sharp edges1 which must have been terrible weapons1 though it is difficult to see how they were used2 probably the mouth was widely opened1 so as to clear the points of the tusks1 and the animal then struck with them1 as a snake does with its fangs4 ,the lower canine was very small and was included in the incisor series1 the shape and function of which it had assumed4 ,thus1 the uintatheres1 with their toothless premaxillaries and1 to all appearances1 eight lower incisors1 formed a curious parallel to the true ruminants 7,pecora71 and1 as in the latter1 they must have had a firm elastic pad on the premaxillaries1 against which the lower incisors could effectively bite1 when cropping the soft plants which formed the diet of these great beasts4 ,the grinding teeth were low-crowned and surprisingly small in comparison with the size of the skull4 ,the premolars and molars were nearly alike and had two or more transverse crests4 ,aside from the altogether exceptional character of the skull1 the skeleton was quite strikingly elephantine in appearance1 so much so1 in fact1 that these animals have repeatedly been referred to the ,proboscidea and some writers are still of the opinion that the two orders were related4 ,there is1 however1 no sufficient ground for this view2 the undeniable likenesses are much more probably to be ascribed to the operation of convergent development4 ,illustration3 ,,fig4 #bca4--,one of the elephantine amblypods 7,uintatherium alticeps7 of the ,bridger stage4 ,male in foreground1 female behind4 ,restored from specimens in the museums of ,yale and ,princeton universities4 ,the neck was of moderate length1 sufficiently long to enable the animal to reach the ground with the lips1 a necessity in the absence of a proboscis4 ,the body was very long and1 as is shown by the length and curvature of the ribs and the great breadth of the hip-bones1 extremely bulky4 ,the limbs were very massive1 and the long bones had lost the marrow-cavities1 being filled with spongy bone1 as in the elephants1 titanotheres and most other very heavy mammals4 ,the bones of the fore-arm and lower leg were separate4 ,the hip- and thigh-bones and shin-bones were remarkably elephantine in character and1 if found isolated1 might readily be referred to some unknown proboscidean1 but the bones of the fore limb were quite different from those of the elephants4 ,the feet likewise had a very proboscidean appearance1 notwithstanding important and significant deviations in structure2 they had the same shortness and massiveness and a similar reduction in the size of the hoofs1 and the presence of all five digits added to the resemblance4 ,undoubtedly1 the feet had the same columnar shape and arrangement of elastic pads4 ,the living animal must have had an appearance quite similar to that of a rather small elephant1 not exceeding six or seven feet in height at the shoulders and therefore not surpassing the largest modern rhinoceroses1 the broad-lipped species of ,africa 7,opsiceros simus74 ,of course1 the head must be excepted from the comparison1 as that was totally unlike the head of any existing creature2 with its long and narrow shape1 its fantastic protuberances and its lack of a proboscis1 it had no suggestion of likeness to any proboscidean4 ,whether the great body was naked1 or clothed with hair1 it is of course impossible to determine with confidence1 but1 all things considered1 it seems unlikely that the hair should have been completely lost in any terrestrial mammal at so early a period4 ,as we have seen in the preceding chapters1 hairy elephants and rhinoceroses continued into and through the ,pleistocene1 not only in the cold regions of the north1 as is shown by the hair of the ,american ,mastodon4 ,in the tropics conditions were different1 and in that uniformly warm climate the loss of hair by the very large mammals probably took place long before the ,pleistocene4 ,at all events1 it is a significant fact that no hairless land mammals are now known in any region which has severe winters4 ,it is true that the middle ,eocene climate over most of ,north ,america was warm-temperate or subtropical1 and the uintatheres may1 in consequence1 have been hairless1 but there is no evidence of this4 ,illustration3 ,,fig4 #bcb4--,skull of ,elachoceras parvum 7lower jaw restored74 ,princeton ,university ,museum4 ,within the limits of the uintathere family1 considerable modification and change may be traced1 which1 as in the case of the ,proboscidea1 principally affected the skull and the general stature4 ,it is hardly worth while to deal separately with the two or more phyla which may be distinguished1 for the differences between them are relatively unimportant4 ,in the uppermost part of the ,bridger stage almost the latest representatives of the family are found and the genus 7,eobasileus7 was of the largest size4 ,these animals had remarkably long and narrow heads and very large1 shovel-shaped nasal protuberances2 in the males the upper canine tusks were very long and curved back nearly in a semicircle4 ,in the middle portion of the stage the species of ,uintatherium were somewhat smaller and had shorter1 wider and higher heads1 the tusks1 though well developed1 were not quite so long1 nor so strongly recurved2 in some species they were nearly straight1 with 8hastate0 or spear-head point4 ,in the same horizon is found a third genus 7,elachoceras7 which was probably a survival persisting from the lower ,bridger1 in which none of these animals and little of anything else has yet been found4 ,elachoceras was hardly half as large as the common species of ,uintatherium and its skull might be described as a preliminary sketch for that of the latter2 the nasal horns were extremely small1 or1 more probably1 entirely absent2 the median pair were mere low knobs1 hardly an inch in height1 and the posterior pair were simply thickenings of the crest which enclosed the top of the cranium on three sides1 scarcely rising above it4 ,this crest itself was much less prominent than in ,uintatherium and the basin-like top of the skull1 in consequence1 very much shallower4 ,the upper incisors and the first premolar had already been lost and the upper canine enlarged into a sabre-like tusk1 which1 however1 was relatively smaller than in the succeeding genera4 ,the grinding teeth were quite the same as in the latter4 ,unfortunately1 the skull of ,elachoceras is the only part of the animal which is known1 but1 so far as that is concerned1 it is precisely what we should expect the forerunner of ,uintatherium to be2 an ancestor made to order could hardly be more diagrammatic4 ,it might1 of course1 be objected that no such relation as that of ancestor and descendant could obtain between these two genera1 because they were contemporaries1 but the case is like that of the ancestral elephants described in the preceding chapter4 ,mritherium and ,palomastodon are found together in the ,egyptian ,oligocene1 the former surviving for a considerable time after it had given rise to the latter1 and in the upper ,eocene only ,mritherium occurs4 ,many similar instances might be given1 just as grandfathers often live long with their grandchildren4 ,in the ,wind ,river stage1 or upper division of the lower ,eocene1 lived the still incompletely known ,bathyopsis1 of which1 however1 sufficient material has been obtained to show that it was much less specialized than any of the ,bridger genera4 ,this genus comprised animals much smaller than its successor1 ,elachoceras of the middle ,eocene1 being smaller than a tapir2 it stood in much the same relation to ,elachoceras as the latter did to ,uintatherium4 ,in the ,american ,museum of ,natural ,history is a highly interesting skull of ,bathyopsis1 which will shortly be described by ,professor ,osborn4 ,the premaxillaries have not been preserved1 and it is therefore impossible to say whether the upper incisors had already been suppressed or not1 and though the upper canine has not been found1 there can be no reasonable doubt that it was a tusk4 ,the lower canine had not yet gone over to the incisor series1 but was a thin though large tusk4 ,there was one more lower premolar1 four in all1 than ,uintatherium possessed1 and all the premolars were somewhat smaller and simpler than the molars4 ,the small skull had a broad and somewhat concave cranial roof1 with slightly raised enclosing crest1 and the horn-like protuberances of the posterior and median pairs were present in an incipient stage4 ,whether those of the nasal pair were also indicated is not known1 but probably they were not4 ,the lower jaw was of very peculiar shape2 the flange of the inferior border was not so well defined as in ,uintatherium1 but had no hinder margin and rose very gradually backward4 ,the series of genera in descending order1 ,eobasileus1 ,uintatherium1 ,elachoceras and ,bathyopsis1 immediately impresses the observer as being a natural phylogenetic series of successive ancestors and descendants4 ,unfortunately1 only the skull is known in the two last named1 but there is no ground for supposing that the discovery of the skeletons would require any alteration in the series as we now have it4 ,no member of this series has yet been found in the ,wasatch1 but there can be no doubt that it was represented in that stage1 for a recent expedition from the ,american ,museum has collected teeth of a ,bathyopsis-like form in still older beds4 ,,suborder ,,pantodonta ,during the older part of the lower ,eocene the uintatheres must have been a rare and unimportant element of the fauna1 at least in those parts of the continent whose history we know4 ,their place was taken by another suborder1 the ,pantodonta1 which was not ancestral to them1 but collaterally related and descended from a common ancestry4 ,the largest and most dominating of ,wasatch mammals was the genus ,coryphodon1 which also occurred in the lower ,eocene of ,europe1 and the species of which ranged in stature from a tapir to an ox1 though of much heavier form than the latter4 ,the latest surviving species lived in the ,wind ,river stage as a contemporary of ,bathyopsis1 but then the suborder gave way to the uintatheres4 ,in ,coryphodon 7see ,fig4 #adb1 p4 #bgi7 the number of teeth was unreduced1 a fact which is recorded in the name of the suborder1 the dental formula typical of all the primitive ungulates being applicable to the genus4 ,this formula was3 i #c_/c1 c #a_/a1 p #d_/d1 m #c_/c1 #b #dd4 ,the upper incisors were rather small1 but functional1 and the canines of both jaws were formidable tusks1 though not rivalling in size the great sabres of the uintatheres2 the premolars had a simpler structure than the molars1 which resembled those of the uintatheres in a general way1 but not closely4 ,the skull differed greatly from that of the uintatheres in having no horn-like protuberances1 and was relatively large and heavy1 the cranium having a broad1 flat roof and no sagittal crest1 and the lower jaw had no descending flange from the inferior border2 in every way this skull was more normal and less bizarre-looking4 ,the neck was proportionately longer than in the uintatheres1 the body long and the tail of medium length2 the trunk-vertebr had surprisingly small and weak spines1 perhaps an indication of aquatic habits4 ,the limbs were quite short and very heavy1 and the bones1 in comparison with those of the uintatheres1 were less proboscidean and more perissodactyl in character4 ,for example1 the femur retained the third trochanter and the long bones had marrow-cavities4 ,the feet1 on the contrary1 were very like those of the uintatheres1 being extremely short and five-toed and with reduced1 nodular hoof-bones2 even in the details of the wrist and ankle joints there was no important difference between the two groups4 ,,suborder ,,taligrada ,none of the ungulate series considered in the foregoing chapters can be traced back to a time earlier than the ,wasatch1 and many of them not so far1 but in the case of the ,amblypoda the line may be carried down through the ,paleocene4 ,in the upper stage of that epoch 7,torrejon7 the order was represented by ,pantolambda 7,fig4 #adc1 p4 #bhe71 a member of the third suborder1 ,taligrada4 ,the best-known species of the genus was an animal with head and body somewhat smaller than those of a sheep and much shorter legs4 ,the teeth were present in unreduced number1 #dd in all2 the canines were tusk-like1 but very much smaller proportionately than those of ,coryphodon2 the premolars were smaller and simpler than the molars1 which closely represent the common starting point1 whence the curious tooth-patterns found in the subsequent genera of the various families were derived4 ,the skull was long and narrow and had a prominent sagittal crest2 the neck was of ordinary length1 about equal to that of the head2 the body was long and the tail very long1 much as in the great cats4 ,the hip-bones were narrow and slender and not bent outward1 having no such breadth as in ,coryphodon4 ,the limbs were short and relatively heavy1 and the various bones were of such primitive character that1 if found isolated and not in association with teeth or foot-bones1 one would hardly venture to consider them as belonging to any hoofed animal2 the humerus had a very prominent deltoid crest and an epicondylar foramen1 and the femur had the third trochanter4 ,the five-toed feet were very short1 and the digits were arranged in a spreading manner and were relatively much more slender than in ,coryphodon4 ,each digit terminated in a flat1 pointed1 well-developed hoof2 evidently there was no elastic pad to bear the weight1 such as recurs in nearly all very heavy ungulates4 ,the gait of the animal was probably semi-plantigrade1 the hoofs being the principal points of support4 ,while ,pantolambda was an undoubted ungulate and a member of the ,amblypoda1 there were many structural features in its skeleton which point to a relationship with the primitive flesh-eaters4 ,in the lower stage of the ,paleocene1 the ,puerco1 the genus ,periptychus would seem to be the most ancient known member of the order1 but it is still very imperfectly understood4 99 99 99 99 99 ,in the mode of evolution of the ,amblypoda1 so far as that is recorded by the fossils1 there is much to recall the development of the ,proboscidea1 though the story began and ended at far earlier dates and may be traced back to a much more primitive stage4 7#a7 ,there was a rapid increase of stature1 especially of bulk1 in the coryphodonts1 but decidedly more gradual in the uintatheres1 which eventually attained a far larger size4 7#b7 ,the upper incisors were suppressed and the canines grew into formidable tusks1 at first straight1 then the superior one1 enlarging still farther1 acquired a curved1 scimitar-like shape1 while the inferior one dwindled and became functionally one of the incisors4 7#c7 ,the grinding teeth remained low-crowned throughout1 but acquired a more complex pattern1 and the premolars became almost like the molars4 7#d7 ,the skull underwent a most remarkable transformation4 ,beginning with a form that might have belonged to almost any of the ancient mammals1 hoofed or clawed1 having very prominent sagittal and occipital crests1 long cranium and short face1 it became in ,coryphodon flat-roofed1 with moderately elongated face1 while in the uintatheres the top of the cranium gradually took on a deeply concave basin-shape and1 with equal gradualness1 three pairs of horn-like protuberances2 the lower jaw developed a great bony flange for the protection of the upper tusks4 ,these peculiarities grew more and more exaggerated and were most striking in the terminal genus of the series1 ,eobasileus4 7#d7 ,unfortunately1 nothing is yet known of the skeleton of ,bathyopsis and ,elachoceras1 so that it is not practicable to follow out all the stages of skeletal modification1 though the general course of development is sufficiently plain4 ,the neck did not change greatly1 except to become very strong and heavy and to grow shorter proportionately as the skull was lengthened4 ,the body remained long throughout the series1 but gained greatly in bulk1 as the stature of the animal increased4 7#e7 ,the limb-bones lost their primitive character1 such as the epicondylar foramen of the humerus and the third trochanter of the femur1 and then1 with the great increase of the weight to be supported1 the marrow-cavities were filled with spongy bone and the hip-bones increased enormously in width2 the femur lost its cylindrical shape and was flattened antero-posteriorly1 which gave it a very elephantine appearance4 ,none of the limb-bones was suppressed or greatly reduced in size1 nor was there any cossification between them4 7#f7 ,the feet early gained their definitive character2 at no time was there any loss of digits1 but the originally divided toes were1 in the genera of the ,wasatch and subsequent stages1 united into the columnar foot1 and the hoofs were reduced from their primitively pointed shape to nodular form4 ,as in the ,proboscidea1 therefore1 there was comparatively little change in the skeleton after the massive and bulky proportions had been acquired1 but great and continual modification of the skull4 ,at the time when the ,amblypoda finally disappeared1 no ungulate had acquired the hypsodont dentition4 ,had the group survived till the middle ,miocene1 a time when the spread of grassy plains so profoundly affected the feeding habits of many herbivorous mammals1 the high-crowned teeth might have been developed in them also1 and this1 in turn1 would have produced other changes in the skull1 making closer the parallel with the ,proboscidea4 ,in conclusion1 a few words may be said concerning the geographical distribution of the ,amblypoda4 ,in the ,paleocene the only known representatives of the order were those of ,north ,america1 but the coryphodonts of the lower ,eocene migrated to the ,old ,world2 indeed1 the genus ,coryphodon was first described and named from ,english specimens1 but there were no such abundance and variety of these animals in ,europe as there were in the western ,united ,states4 ,the uintatheres were strictly ,north ,american in distribution and no member of the suborder has ever been found outside of this continent4 ,animals referred to the ,amblypoda by some authorities have been obtained in the ,oligocene and ,miocene of ,south ,america1 but the assignment has been made upon insufficient evidence4 7,see p4 #ejh47 ,,order ,,condylarthra ,the ,condylarthra were a group of exceedingly primitive ungulates1 which served to connect the hoofed and clawed mammals in quite an intimate manner4 ,so few indeed were the distinctively ungulate characters which they had acquired1 that it is still premature to make any positive statements regarding their geographical distribution1 because unusually well-preserved specimens are required to make sure of their presence in any particular region4 ,concerning ,north ,america there is no room for question1 and there is hardly any doubt that they existed in the ,paleocene of ,europe4 ,the ,south ,american remains which have been referred to this order may very well prove eventually to belong to it properly1 but until both feet and skulls have been obtained in unequivocal association1 the reference can be only tentative4 ,in ,north ,america they ranged through the ,paleocene and lower ,eocene1 but are not known from any subsequent formation1 and even in the ,wind ,river only a few stragglers survived4 ,the principal ,american families and genera are as follows3 ,i4 ,,meniscotheriid4 ,meniscotherium1 ,wasatch and ,wind ,river4 ,,ii4 ,,phenacodontid4 ,protogonodon1 ,puerco4 ,euprotogonia1 ,torrejon4 ,phenacodus1 ,wasatch and ,wind ,river4 #a4 ,phenacodontid ,the typical ,wasatch genus ,phenacodus1 which is very fully known from nearly complete skeletons1 included species which varied in size from a fox to a small sheep2 the same genus occurred in the ,wind ,river1 but not later4 ,phenacodus had the unreduced dental formula3 i #c_/c1 c #a_/a1 p #d_/d1 m #c_/c1 #b #dd4 ,illustration3 ,,fig4 #bcc4--,skeleton of the ,wasatch condylarth1 ,phenacodus primvus4 ,american ,museum4 ,for restoration1 see ,fig4 #ada1 p4 #bgh4 ,the incisors were small and simple1 the canines tusk-like1 but of no very great size1 the premolars smaller and simpler than the molars4 ,the latter were of the quadrituberculate pattern1 of four simple1 conical cusps arranged in two pairs1 a pattern which is common to the earlier and less specialized members of many ungulate groups4 ,the skull was long1 narrow and low1 with long and well-defined sagittal crest4 ,as in primitive skulls generally1 the cranial region was long and the face short1 the eyes being very far forward2 this does not imply large brain-capacity1 indeed1 the brain was very small1 but merely that the portion of the skull behind the eyes was relatively long4 ,the jaws were short and shallow1 in accordance with the small and low-crowned teeth which they carried4 ,the neck was of medium length1 but the body was elongate and the tail was very long and stout4 ,the hip-bones were narrow and slender1 as in primitive ungulates generally4 ,the limbs were short and stout and retained many very primitive characteristics4 ,the humerus had a prominent deltoid crest and an epicondylar foramen2 the fore-arm bones were separate and the ulna quite unreduced1 being almost as stout as the radius4 ,the femur had the third trochanter and the leg-bones were distinct1 though the fibula was slender4 ,the feet1 which were short1 had five digits each1 but the third toe was enlarged1 while the first and fifth were shortened1 as though preparing to disappear and thus give rise to a three-toed perissodactyl foot4 ,the ankle-bone 7astragalus7 had a rounded1 convex lower end1 fitting into the navicular1 so that it might readily be taken for that of a clawed mammal4 #b4 ,meniscotheriid ,a second family of ,condylarthra was represented in the lower ,eocene by the genus ,meniscotherium and was in some respects considerably more advanced than the phenacodonts4 ,these were small animals1 in which the molars had acquired a crescentic pattern1 recalling that seen in the early horses and in the titanotheres and chalicotheres1 and other perissodactyl families4 ,in the upper molars the two external cusps had been so extended as to form a continuous outer wall1 each of the cusps having a concave external face and the two uniting in a prominent median ridge4 ,the lower molars had two crescents1 one behind the other1 as in several families of both perissodactyls and artiodactyls4 ,the body and tail were long1 the limbs relatively longer and lighter than those of ,phenacodus and the five-toed feet were so like those of the modern conies1 or klipdasses1 of ,africa and ,asia ,minor1 that by some investigators the family has been referred to the same order1 the ,hyracoidea1 but the suggestion is not a probable one4 ,it is much more likely that these problematical little meniscotheres were merely a short-lived branch of the ,condylarthra4 ,illustration3 ,,fig4 #bcd4--,lower ,eocene condylarth1 ,meniscotherium terr-rubr4 ,restored from a skeleton in the ,american ,museum4 ,the condylarths were quite abundantly represented in the ,paleocene1 where the genus ,euprotogonia was the forerunner of the ,wasatch ,phenacodus1 but had an even more primitive type of dentition4 ,the upper molars were not quadritubercular1 but tritubercular1 the three cusps arranged in a triangle1 the two outer ones forming the base and the single inner one the apex4 ,this type of upper molar was1 or is still1 common to the primitive and unspecialized members of a great many mammalian orders1 marsupials1 insectivores1 rodents1 carnivores1 lemurs1 artiodactyls1 etc41 and there is strong reason to believe that the tritubercular molar was the common starting point for almost all types of mammalian dentition4 ,however that may be1 ,euprotogonia is of great interest as materially helping to close the gap between the clawed and the hoofed mammals1 belonging1 as it did1 to the latter and yet retaining in dentition1 limbs and feet so many characteristics of the former4 ,condylarthra were probably present in the lowest ,paleocene 7,puerco stage71 but the material so far obtained is so fragmentary that there can be no certainty on this point4 ,it is not at all probable that any of the ,north ,american ,condylarthra should be regarded as ancestral to any of the more advanced ungulate groups2 on the contrary1 they would appear to have come to an end in the ,wind ,river1 leaving no descendants behind them4 ,it is further true1 as was mentioned above1 that the presence of ,condylarthra in other continents1 while very probable1 cannot be positively asserted1 because the evidence is incomplete4 ,yet it would be a great mistake to assume1 for this reason1 that these most primitive of ungulates were devoid of evolutionary importance and interest4 ,as is so often the case1 where1 in the absence of the direct ancestry1 the collateral relations afford very valuable information as to the course of descent and modification1 the ,condylarthra throw useful light upon the origin of the ungulate groups4 ,it is extremely probable that the condylarths1 or some very similar series of primitive hoofed mammals1 had a very wide and perhaps cosmopolitan range at the end of the ,cretaceous and beginning of the ,tertiary period1 and that1 in the still unidentified region1 where the artiodactyls and perissodactyls arose1 it was from a condylarthrous ancestry4 ,possibly1 all the other ungulate orders may yet be traced back to the same stock1 but it is rather more likely that the ungulates include several series of quite independent origin4 ,at all events1 it is quite certain that the clawed mammals long antedated the hoofed types and that the latter arose1 either once or at several separate times1 from the former4 ,the ,condylarthra show how one1 at least1 of these transitions was effected1 and thus1 in principle1 how all were accomplished4 ,,chapter ,,xii ,,history ,,of ,,the ,,toxodontia 7,,or ,,notoungulata7 ,it is a regrettable circumstance that1 while the successive ,tertiary faunas are very fully represented in ,south ,america1 approximately complete skeletons have1 as yet1 been obtained from only a few of the various stages2 from the others the known material is very fragmentary and largely made up of teeth and jaws4 ,no doubt1 the history of fossil-collecting in ,north ,america will1 in due course of time1 be repeated in the southern continent and more and more complete and satisfactory specimens be obtained4 ,at present1 however1 it is not possible to trace the modifications of structure in any given series with such detail as in those which were developed within the limits of ,arctoga4 ,no such story as that of the horses1 the rhinoceroses or the camels1 can yet be told of the ,south ,american groups1 whatever future exploration may teach us4 ,nevertheless1 much has already been learned concerning the strange creatures that once inhabited the ,neotropical region and long ago vanished completely1 leaving no trace in the modern world4 ,as was mentioned in ,chapter ,,vi1 on the present geographical distribution of mammals1 ,south ,america is to-day the richest and1 after ,australia1 the most peculiar zologically of all the regions4 ,all of the modern hoofed animals found in that continent at present1 the tapirs1 peccaries1 llamas and deer1 are immigrants derived at a comparatively late date from the north1 but throughout the ,tertiary and the ,pleistocene there were several indigenous types of ungulates1 and of these the largest and most varied assemblage was that included in the order ,toxodontia4 ,the most important and best known of the families and genera are listed in the table3 ,suborder ,,toxodonta4 ,toxodonts ,proper ,i4 ,,toxodontid4 ,toxodon1 up4 ,plio4 and ,pamp4 ,xotodon1 do4 ,trigodon1 ,monte ,hermoso4 ,nesodon1 ,santa ,cruz4 ,adinotherium1 do4 ,pronesodon1 ,deseado4 ,proadinotherium1 do4 ,,ii4 ,,notohippid4 ,notohippus1 ,patagonian4 ,rhynchippus1 ,deseado4 ,morphippus1 do4 ,,iii4 ,,leontiniid4 ,leontinia1 ,deseado4 ,colpodon1 ,patagonian4 ,suborder ,,typotheria4 ,typotheres ,i4 ,,typotheriid4 ,typotherium1 ,plioc4 and ,pleist4 ,eutrachytherus1 ,deseado4 ,,ii4 ,,interatheriid4 ,interatherium1 ,santa ,cruz4 ,protypotherium1 do4 ,,iii4 ,,hegetotheriid4 ,hegetotherium1 ,santa ,cruz4 ,pachyrukhos1 ,santa ,cruz to ,pampean4 ,,iv4 ,,notopithecid4 ,notopithecus1 ,casa ,mayor4 ,adpithecus1 do4 ,v4 ,,arch,,opithecid4 ,henricosbornia1 ,casa ,mayor4 ,,vi4 ,,arch,,ohyracid4 ,archohyrax1 ,deseado4 ,suborder ,,entelonychia4 ,homalodotheres ,i4 ,,notostylopid4 ,notostylops1 ,casa ,mayor4 ,,ii4 ,,isotemnid4 ,isotemnus1 ,casa ,mayor4 ,pleuroclodon1 ,deseado4 ,,iii4 ,,homalodontotheriid4 ,homalodontotherium1 ,santa ,cruz4 ,asmodeus1 ,deseado4 ,proasmodeus1 ,astraponotus ,beds4 ,thomashuxleya1 ,casa ,mayor4 ,suborder ,,pyrotheria4 ,pyrotheres ,,pyrotheriid4 ,pyrotherium1 ,deseado4 ,propyrotherium1 ,astraponotus ,beds4 ,carolozittellia1 ,casa ,mayor4 ,paulogervaisia1 do4 ,,suborder ,,toxodonta4 ,,toxodonts ,,proper ,among the remarkable animals which ,charles ,darwin found in the ,pampean deposits of ,argentina and took with him to ,england1 was a skull of one which ,sir ,richard ,owen named ,toxodon1 or 8,bow-,tooth10 from the strongly curved grinding teeth1 those of the opposite sides almost meeting in the median line above the hard palate4 ,for many years ,toxodon1 of which hardly anything was known1 save the skull and teeth1 was a zological puzzle and no one was able to reach any satisfactory conclusion as to its systematic position and relationships1 as all the attempts made to force it into one of the known ungulate groups were obvious failures4 ,the discovery of complete skeletons1 two of which are mounted in the ,la ,plata ,museum1 showed the necessity of making a new group for its reception1 as ,owen had originally proposed4 ,through the exploration of ,argentina and its ,patagonian provinces1 the history of the suborder was followed far back into the ,tertiary period and its indigenous character demonstrated4 ,this and all the other subdivisions of the ,toxodontia were exclusively ,neotropical in distribution1 and none have been found farther north than ,nicaragua and there only in the ,pleistocene4 ,the suborder was represented in the ,pampean beds by several genera1 which differed in size and in the complexity of the grinding teeth1 but only of ,toxodon is the skeleton at all fully known4 ,the ,pampean species of this genus were massive1 elephantine creatures1 rivalling the largest rhinoceroses in bulk1 but not equalling them in height4 ,the teeth were all thoroughly hypsodont and apparently continued to grow throughout life without forming roots2 the dental formula was3 i #b_/c1 c #j_/j1 p #c_/c1 m #c_/c1 #b #cd4 ,the first upper incisor was broad and chisel-shaped1 the second more tusk-like1 but in some species these proportions were reversed2 the lower incisors were procumbent1 pointing straight forward1 and of these the third was the largest4 ,the canines were lost and there was a long1 toothless gap behind the incisors4 ,the premolars were smaller and simpler than the molars1 and the anterior ones were very small and were frequently shed at an early stage1 making the number of these teeth variable in different specimens4 ,the upper molars also were of quite simple pattern2 the broad and smooth external wall showed no distinct signs of a division into cusps1 and from it arose two oblique transverse ridges2 the deep cleft or valley which separated these ridges was divided and made ,y-shaped on the grinding surface by a prominent spur from the outer wall between the two principal crests4 ,the lower molars were composed of two crescents1 one behind the other1 of which the posterior one was very much longer1 and both were very narrow transversely4 ,the skull had shortened nasal bones1 an indication that some sort of a proboscis or prehensile upper lip was present4 ,there was no trace of a horn1 and the general aspect of the skull was not unlike that of one of the hornless rhinoceroses1 except for its great vertical depth2 the sagittal crest was very short and had almost disappeared4 ,the auditory apparatus was very extraordinary1 though it can hardly be described without an undue employment of anatomical terms2 suffice it to say that in addition to the usual outer ear-chamber1 formed by the inflated tympanic bone1 there was a second chamber in the rear wall of the skull1 communicating with the first by a canal4 ,this arrangement would seem to imply an unusual keenness in the sense of hearing4 ,the external entrance to the ear was placed very high up on the side of the head1 as in the pigs and in many aquatic mammals1 suggesting that ,toxodon was more or less amphibious4 ,the anterior1 or symphyseal1 region of the lower jaw was very broad1 flattened and shovel-like1 hardly projecting at all below the plane of the lower incisors4 ,the neck was short and stout1 the body long and extremely bulky1 having an immense1 almost hippopotamus-like girth2 the spines of the anterior dorsal vertebr were very long1 making a high hump at the shoulders4 ,the limbs were short and very heavy1 the bones very massive and with large projections for muscular attachments4 ,the fore leg was much shorter than the hind1 depressing the neck and head in very curious fashion4 ,the shoulder-blade was rather narrow1 the spine without acromion or distinct metacromion2 the hip-bones were greatly expanded and turned outward1 quite in elephant-like fashion1 a character which almost invariably accompanies great increase in bodily mass4 ,the thigh-bone was also very elephantine in appearance1 a likeness due to its shape and proportions1 to the loss of the third trochanter and the flattening of the shaft1 so that the width much exceeded the antero-posterior thickness4 ,all of these characters are1 as a rule1 associated with greatly augmented weight and have been independently acquired in several series of large and massive animals1 elephants1 uintatheres1 titanotheres1 and to this list should be added the toxodonts4 ,in the fore-arm the bones were separate and the ulna was quite unreduced and very stout1 but in the lower leg1 which was very short in comparison with the thigh1 the tibia and fibula were cossified at the upper end1 but not at the lower1 a most exceptional arrangement4 ,the feet were surprisingly small and had but three digits1 the reduction from the original five having proceeded to that extent before the process was arrested by augmenting weight4 ,the heel-bone 7calcaneum7 was so articulated with the other bones of the tarsus as to project almost straight backward1 nearly at a right angle to the position normal in a digitigrade foot1 a feature which is not known to occur in any other mammal4 ,the hoof-bones were so small and nodular that the foot must have been of the columnar type1 the weight resting upon the usual elastic pad4 ,the restoration 7,fig4 #aba1 p4 #bag7 shows ,toxodon as a very heavy1 slow-moving1 water-loving animal2 the aquatic habits are1 of course1 conjectural1 but the general proportions are accurately given by the skeleton4 ,from the ,pleistocene1 ,toxodon may be followed back without notable change to the ,pliocene1 but there it was in association with the last of a curious phylum1 the genus ,trigodon 7,fig4 #ach1 p4 #bfc71 as yet known only from the skull4 ,in these animals a very prominent bony knob or boss on the forehead clearly demonstrates the former presence of a large1 rhinoceros-like1 frontal horn4 ,but very few of the indigenous ,south ,american ungulates possessed horns1 or horn-like protuberances of the skull1 and all of these so far discovered belonged to the suborder ,toxodonta4 ,trigodon was1 from present knowledge1 the only horned creature of its time and region1 for the deer and antelopes which had probably arrived in ,south ,america had not advanced so far south as ,argentina4 ,another very peculiar feature of this genus was that the lower incisors were present in uneven number1 two on each side and one in the middle4 ,nothing has been found of the skeleton1 but it was doubtless that of a smaller and somewhat lighter ,toxodon4 ,illustration3 ,,fig4 #bce4--,skull of ,toxodon1 ,pampean formation1 the upper molars much broken4 ,la ,plata ,museum4 ,the material from the lower ,pliocene adds nothing to our knowledge of this suborder1 but in the ,santa ,cruz time of ,patagonia1 which was ,miocene1 it was very abundantly represented and preponderatingly by the genus ,nesodon1 which was the first discovered member of the marvellous ,santa ,cruz fauna1 named nearly #gj years ago by ,sir ,richard ,owen4 ,it also chanced that ,owen's specimen was the imperfect lower jaw of a young animal with the milk-teeth1 which were mistaken for the permanent dentition1 and when the latter was found long afterwards1 it was naturally supposed to belong to a different animal and received a different generic name4 ,nor was this all2 the changes which took place in the appearance and relative size of the permanent teeth within the life-time of the individual were so remarkable1 that the successive stages of development were by several investigators supposed to be distinct genera and species and named accordingly4 ,in this way nearly #cj different names have1 at one time or another1 been assigned to the common species1 ,n4 imbricatus2 and it was not until the late ,dr4 ,ameghino had brought together a complete series of skulls and jaws illustrating these changes1 and showing the gradual transition from one to the other1 that the confusion could be cleared up4 ,illustration3 ,,fig4 #bcf4--,skull of ,santa ,cruz toxodont1 ,nesodon2 same scale of reduction as ,fig4 #bce4 ,there was a long hiatus in time between ,toxodon and ,nesodon and so great was the structural difference between them1 that there is much doubt whether the latter was directly ancestral to the former2 in any event1 ,nesodon so nearly represents what the desired ancestor must have been1 as to serve for all practical purposes of the study4 ,all the species of this ,santa ,cruz genus were much smaller animals than the species of ,toxodon1 ,n4 imbricatus being no longer than a tapir1 with considerably shorter legs1 and of much slighter and more slender build than ,toxodon1 though every tooth and every bone proclaims its relationship to the latter4 ,in ,nesodon the dental formula was unreduced2 i #c_/c1 c #a_/a1 p #d_/d1 m #c_/c1 #b #dd1 though several of the teeth were much reduced in size1 so as to have lost their functional importance1 and frequently individuals are found in which one or more of these insignificant teeth are lacking4 ,the first upper incisor was a broad1 chisel-shaped tooth1 which continued to grow for a period1 then formed its root1 and growth ceased2 the second incisor was a pointed1 triangular tusk1 which grew throughout life1 becoming longer with advancing age2 while the third1 which was lost in ,toxodon1 was small and unimportant4 ,in the lower jaw the first and second incisors were chisel-like and had a limited growth2 being rather narrow1 they both bit against the broad first upper incisor2 the third incisor was a persistently growing tusk1 not so large as the upper one1 against the posterior face of which it impinged and was obliquely truncated by wear1 so that its length was limited1 while the upper tusk continued to elongate and was made narrower and sharper by wear4 ,all the lower incisors were far less procumbent than in ,toxodon1 and were directed obliquely upward and forward4 ,the remarkable changes of appearance which1 as mentioned above1 took place within the life-time of the individual1 were largely due to the differential growth of the incisors4 ,the milk-incisors were all nearly alike and formed no tusks2 when the permanent incisors were first protruded1 the first upper and the first and second lower were large and the tusks were not visible1 and1 when the latter did appear1 they were for some time smaller than the other incisors4 ,these1 however1 formed roots and ceased to grow1 actually becoming smaller with advancing age1 for the crowns narrowed to the roots and1 the more they were worn down1 the smaller they became4 ,the tusks1 on the other hand1 grew throughout life and became larger as the other incisors were reduced by wear1 and thus the whole appearance of the anterior part of the jaw was totally changed4 ,this mode of forming the tusks by the enlargement of the second upper and third lower incisor is an unusual one1 though it was repeated in another ,south ,american ungulate order1 the ,litopterna1 and nearly so in the ,proboscidea1 in which both upper and lower tusks were the second of the three original incisors4 ,in both jaws1 the canines of ,nesodon were insignificant and sometimes absent4 ,the premolars1 which were smaller and simpler than the molars1 had quite high crowns1 but early ceased to grow and formed long roots4 ,the molars were truly hypsodont and formed no roots till late in life2 they were constructed on the same plan as those of ,toxodon1 but were decidedly more complex1 the upper ones having several spurs and crests given off inward from the external wall1 in addition to the two principal transverse crests1 and they had a certain superficial likeness to the teeth of a rhinoceros4 ,as in ,toxodon1 these upper molars were curved inward1 so as almost to meet those of the opposite side above the palate4 ,the lower molars had the same bicrescentic plan as in ,toxodon1 but were more complicated1 and in the concavity of the hinder crescent was a vertical pillar1 which was well-nigh universal among the indigenous ,south ,american ungulates4 ,if ,nesodon was really the ancestor of ,toxodon1 then the development of the grinding teeth must have been a process of completing the hypsodontism1 until the teeth grew persistently1 never forming roots1 and1 at the same time1 of simplifying the pattern4 ,this is contrary to the usual course of evolution1 in which the pattern grew more complex in the successive stages2 but such steadily increasing complexity was not invariable1 and several instances of undoubted simplification are known among mammals1 though not yet in other ungulates4 ,only the recovery of the intermediate genera will enable us to determine whether ,nesodon was the actual ancestor of ,toxodon1 or whether it was merely one of a short-lived branch from the main stem1 in which the teeth had acquired an unusual degree of complexity4 ,illustration3 ,,fig4 #bcg4--,nesodon imbricatus1 ,santa ,cruz stage4 ,restored by ,c4 ,knight from a skeleton in the museum of ,princeton ,university4 ,a few years ago ,dr4 ,ameghino announced the very surprising discovery that1 instead of having merely the normal arrangement of two dentitions1 the milk and the permanent1 ,nesodon developed three successive dentitions1 one preceding the milk-series1 and therefore called pre-lacteal4 ,in certain other mammals traces of a pre-lacteal series had already been found1 in the shape of tooth-germs1 which never attain full development or even cut the gum2 and quite recently ,dr4 ,ameghino has shown that in the tapir at least one functional pre-lacteal premolar is formed4 ,the significance of this fully developed pre-lacteal dentition in ,nesodon is not yet clear1 though it seems reasonable to suppose that it was the almost uniquely late retention of a primitive character4 ,the skull was closely similar to that of ,toxodon1 on a smaller scale1 but there were several minor differences1 which were1 in part1 conditioned by the larger and much more completely hypsodont teeth of the ,pampean genus1 as well as by its generally increased size and bulk4 ,in ,nesodon the sagittal and occipital crests were much more prominent and the former was much longer1 while the thickening of the cranial bones was in only an incipient stage4 ,the nasal bones were considerably longer4 ,the jaws were lower and shallower1 in correlation with the less perfectly hypsodont teeth1 and in the lower jaw the chin was much more erect and rounded4 ,the entire head of this curious ,santa ,cruz animal had something remarkably rodent-like in its appearance1 though it is quite inadmissible to suppose that the likeness was due to relationship4 ,the skeleton was far smaller and lighter and otherwise differently proportioned from that of ,toxodon1 but there was1 nevertheless1 a close agreement between the two genera4 ,the neck was of moderate length and thickness1 the body long and heavy1 but with no such relative bulk as in the ,pampean genus4 ,the hump at the shoulders1 as indicated by the spines of the anterior dorsal vertebr1 though already well defined1 was less prominent4 ,the shoulder-blade 7scapula7 was relatively broader than in ,toxodon1 its spine had a distinct acromion and two very long and conspicuous processes given off backward from the spine1 only one of which1 and that a mere vestige1 is indicated in ,toxodon4 ,the hip-bones were almost parallel with the backbone and were not nearly so broad or so everted as in the latter1 a difference which is amply accounted for by the great discrepancy in girth4 ,illustration3 ,,fig4 #bch4--,left pes of ,toxodon4 ,la ,plata ,museum4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cn4 #a and #b1 cossified internal and middle cuneiforms4 ,cn4 #c1 external cuneiform4 ,cb41 cuboid4 ,the limbs were of nearly equal length and there was no such shortening of the fore-arm or elongation of the thigh as in ,toxodon1 and so the descent of the backbone forward1 which gave such grotesqueness to the skeleton of the latter1 was far less pronounced4 ,the limb-bones were rather slender1 in size and proportions not unlike those of a tapir1 but in structure very like the very much larger and more massive ones of ,toxodon4 ,the bones of the fore-arm were separate1 but those of the lower leg were cossified in the same exceptional manner as in the ,pampean genus1 that is1 the upper ends1 but not the lower1 were fused together4 ,the thigh-bone was not flattened1 but had the normal cylindrical shaft and a conspicuous third trochanter4 ,the feet1 in which the digits were already reduced to three1 were extremely small in comparison with the size of the animal2 in structure1 they were almost identical with those of ,toxodon1 but were far narrower and more slender4 ,the heel-bone 7calcaneum7 articulated with the other bones of the tarsus in a normal manner4 ,the digits were well separated and the hoof-bones quite strongly developed1 indicating that the hoofs were functional1 supporting most of the weight4 ,in short1 the difference in the external appearance of the feet between the two genera was much the same as between the tapirs and rhinoceroses4 ,the species of ,nesodon1 of which many have been named on very questionable grounds1 differed but little in size and were of such variable and fluctuating character that a proper discrimination of them is exceedingly difficult4 ,one of these species 7,n4 cornutus7 gives indications of having possessed a small dermal horn on the forehead and was thus a possible ancestor of ,trigodon4 ,illustration3 ,,fig4 #bci4--,left pes of ,nesodon1 ,princeton ,university ,museum4 ,letters as in ,fig4 #bch and scale of reduction the same4 ,a second phylum of the suborder was represented in the ,santa ,cruz stage by the genus ,adinotherium1 the species of which1 not equalling a sheep in size1 were very much smaller animals than those of ,nesodon1 but closely like them in other respects4 ,the dentition1 including the pre-lacteal series1 and the skull were almost identical in the two genera1 with the exception that a large proportion of the individuals of ,adinotherium had the small frontal horn1 while others had no trace of it4 ,while it is quite possible that the presence or absence of the horn1 which was always inconspicuous1 may have been a matter of specific distinction1 a more probable explanation is that it was a sexual character1 the males horned and the females hornless4 ,much the same thing is to be observed in the modern ,javan ,rhinoceros 7,r4 sondaicus7 in which the females have a very small horn1 or none at all1 and the males a large one4 ,in the skeleton also there were few differences1 other than those of size1 between ,adinotherium and ,nesodon2 the former was not only smaller1 but also lighter and more slender proportionately1 and there was no hump at the shoulders1 the spines of the dorsal and lumbar vertebr all reaching the same level1 so that the back must have been nearly straight in the living animal4 ,from the more general and constant presence of the frontal horn1 ,adinotherium was more probably the ancestor of the horned ,trigodon than was ,nesodon1 but until the intermediate forms shall have been recovered1 no definite decision can be made4 ,illustration3 ,,fig4 #bdj4--;,adinotherium ovinum1 small1 horned toxodont of the ,santa ,cruz4 ,restored from a skeleton in the museum of ,princeton ,university4--,note the minute horn on the forehead4 ,the same or very nearly the same genera of the family ,toxodontid lived in the ,patagonian and ,deseado stages1 but there the record breaks off and can1 for the present at least1 be followed no farther4 ,it remains to be determined whether the series originated in regions farther to the north1 or whether the ancestral types will be found in ,patagonia4 ,the other two families are still very incompletely known1 but sufficiently to justify their inclusion in the present suborder4 ,in the ,leontiniid1 which are known only from the ,deseado stage 7,leontinia71 we have a curious variant of the toxodont type4 ,the tusks were decidedly smaller than in the ,santa ,cruz members of the preceding family1 the grinding teeth with lower crowns and simpler structure4 ,the skull was much like that of ,nesodon1 but the anterior nasal opening was of quite a different shape1 being carried much farther back on the sides1 so that the nasal bones had a far longer portion which was freely projecting and unsupported2 these bones were shorter and much thicker than in the ,santa ,cruz genera and1 to all appearances1 supported a small1 median horn on their anterior ends4 ,the feet1 so far as they have been recovered1 did not differ in any significant manner from those of the preceding family4 ,illustration3 ,,fig4 #bda4--,skull of ,adinotherium1 top-view1 showing the rugosity on the forehead for the small frontal horn4--,princeton ,university ,museum4 ,another imperfectly known family1 that of the ,notohippid1 occurred in the ,patagonian stage1 but was most abundant in the ,deseado1 where several genera of it have been found4 ,these animals had mostly hypsodont teeth1 forming roots in old age1 and the teeth were in closed series1 but there was no tusk-like enlargement of the incisors4 ,in the later genera1 those of the ,patagonian stage 7,notohippus1 ,argyrohippus71 the crowns of the grinding teeth had a thick covering of cement1 and those of the lower jaw had some resemblance1 though not at all a close one1 to the teeth of horses4 ,the skull also had a certain suggestion of likeness to the horses and ,dr4 ,ameghino was persuaded that these animals were ancestors of the horses4 ,the family went back to the ,astraponotus stage1 but can be traced no farther4 ,,suborder ,,typotheria4 ,,typotheres ,this suborder was composed of much smaller animals than the ,toxodonta and contained no large forms2 some1 indeed1 were exceedingly small1 no larger than rabbits4 ,it was much the most diversified of the suborders1 as is made evident by the table of families and genera4 ,two of these families1 the ,typotheriid and the ,hegetotheriid1 continued into the older ,pleistocene4 ,of the former there was the genus first named and described1 ,typotherium1 which has given its name to the family and suborder1 and the species of which were much the largest of the entire group1 almost equalling a large pig in size4 ,at the first glance this genus might easily be mistaken for a large rodent1 and indeed it has actually been referred to that order1 but the resemblance was a purely superficial one and involved no relationship4 ,in ,typotherium the teeth were considerably reduced in number1 the formula being3 i #a_/b1 c #j_/j1 p #b_/a1 m #c_/c1 #b #bd4 ,the first incisor in each jaw was a broad1 scalpriform1 persistently growing tooth1 which much resembled the corresponding tooth in the rodents1 but was not1 as it is in the latter1 worn to a sharp chisel-edge by attrition1 but was abruptly truncated4 ,there was a second similar1 but much smaller1 tooth in the lower jaw2 the other incisors and all the canines had been lost and the premolars reduced to two in the upper and one in the lower jaw4 ,the molars were large1 persistently growing and thoroughly hypsodont2 in pattern they were very similar to those of ,toxodon4 ,the skull without the lower jaw was low and the cranial portion broad and flattened1 but retaining a long sagittal crest4 ,the eye-sockets were nearly1 but not quite1 closed behind by the very long and slender postorbital processes of the frontal bones4 ,in front of the eyes the face was suddenly constricted into a long1 narrow rostrum1 and it is this shape of the skull which1 together with the persistently growing1 scalpriform incisors1 gave such a rodent-like appearance to the head4 ,the auditory region had the same remarkable structure as in the ,toxodonta4 ,the lower jaw had a short horizontal portion and very high vertical portion1 which gave the head great vertical depth4 ,the skeleton1 so far as it is known1 was decidedly more primitive than that of the contemporary ,toxodon1 as is shown by the presence of collar-bones 7clavicles7 and by the larger number of digits1 five in the front foot and four in the hind4 ,the hoof-bones1 or ungual phalanges1 were narrow1 pointed and nail-like1 though in the hind foot they were broader and more hoof-like4 ,little can be done as yet in tracing back the history of this family1 the ,santa ,cruz beds having yielded no member of it4 ,in the ,deseado stage1 the genus ,eutrachytherus differed surprisingly little from ,typotherium1 in view of the long hiatus in time between them4 ,the ,deseado genus already had thoroughly hypsodont and rootless teeth1 and the molar pattern was quite the same as in ,typotherium1 but the teeth were much more numerous1 the formula being3 i #c_/b1 c #a_/a1 p #d_/d1 m #c_/c1 #b #db4 ,nothing is known of the skeleton4 ,the family arose probably from one of the ,eocene families 7,archopithecid or ,aclodid7 with low-crowned teeth1 but the connection cannot be made out4 ,presumably1 the development of this family ran its chief course in some part of ,south ,america far to the north of the fossil-beds of ,patagonia4 ,the second family which was represented in ,pampean times was that of the ,hegetotheriid1 and the sole genus of it which survived so late was ,pachyrukhos1 a little creature no larger than a rabbit4 ,the genus went back without any noteworthy change to the ,santa ,cruz stage of the ,miocene1 from which complete skeletons have been obtained4 ,the dental formula was nearly as in ,typotherium3 i #a_/b1 c #j_/j1 p #c_/c1 m #c_/c1 #b #cj1 and the enlarged1 rootless and scalpriform incisors were similar4 ,the grinding teeth were thoroughly hypsodont and had a thin coating of cement2 the molar-pattern was fundamentally like that of ,nesodon1 in simpler form1 but can be seen only in freshly erupted and unworn teeth4 ,the skull was very rodent-like in appearance1 its flat top and narrow1 tapering facial region1 and the gnawing incisors adding much to the resemblance4 ,the very large eye-sockets and the enormously developed auditory region suggest nocturnal habits1 and1 no doubt1 the timid1 defenceless little creatures hid themselves by day1 perhaps in burrows4 ,the enlargement of the accessory auditory chambers1 which all of the ,toxodontia possessed1 reached its maximum in ,pachyrukhos1 and the chambers formed great1 inflated protuberances at the postero-external angles of the skull4 ,the neck was short1 the body long and the tail very short1 much like that of a rabbit4 ,collar-bones were present1 as they probably were in all of the other members of the suborder ,typotheria1 though this has not been definitely ascertained in all cases4 ,the limbs were relatively long1 especially the hind legs1 and very slender2 the bones of the fore-arm were separate1 but those of the lower leg were cossified at both ends4 ,the feet1 which had four digits each1 were of unequal size1 the posterior pair being much longer than the anterior1 and the hoofs were long1 slender and pointed1 almost claw-like4 ,the entire skeleton suggests a leaping gait and its proportions and general appearance were remarkably like those of a rabbit-skeleton4 ,in the restoration 7,fig4 #cjj1 p4 #fci7 ,mr4 ,knight has followed these indications and drawn an animal which might readily be mistaken for a curious1 short-eared rabbit2 and there is every justification for doing this1 though the character of the fur and the form of the ears are1 of course1 merely conjectural4 ,perhaps the ears are too small4 ,associated with ,pachyrukhos in the ,santa ,cruz stage was another genus of the family1 ,hegetotherium1 which1 though it cannot possibly have been ancestral to the former1 yet serves to indicate1 in general terms1 what the ancestor must have been4 ,this is another example of the long-continued survival of the more primitive together with the more advanced and specialized form4 ,hegetotherium persisted into the ,pliocene1 but is not known from the ,pleistocene4 ,in this genus one upper and two lower incisors were already enlarged1 rootless and scalpriform1 but none of the teeth had been lost2 it is interesting to note1 however1 that the teeth which were lacking in ,pachyrukhos were all very small and ready to disappear4 ,the ,santa ,cruz species of ,hegetotherium were considerably larger and more robust animals than those of ,pachyrukhos4 ,both of these genera were preceded by very similar1 almost identical forms in the ,patagonian1 ,deseado and ,astraponotus stages1 but the family cannot be definitely traced farther back than the lower ,oligocene1 but it very probably arose from some one of the groups1 with low-crowned teeth1 of the ,casa ,mayor stage4 ,illustration3 ,,fig4 #bdb4--,santa ,cruz typothere 7,protypotherium australe7 and armadillo 7,stegotherium tesselatum74 ,restored by ,c4 ,knight from skeletons in the museum of ,princeton ,university4 ,the family ,interatheriid was1 in most respects1 more conservative and underwent less change than either of the preceding groups4 ,a persistently primitive type was the genus ,protypotherium1 which appeared for the last time in the ,pliocene of ,monte ,hermoso1 but was much more abundant and better preserved in the ,santa ,cruz4 ,the animal was small and had the full complement of teeth1 which were arranged in each jaw in a continuous series1 and were fully hypsodont and rootless1 except incisors and canine1 which were rooted4 ,none of the incisors was specially enlarged1 but there was a gradual transition of increasing size and complexity from the incisors to the molars4 ,a remarkable feature of this genus was the deeply cleft form of the lower incisors1 giving them a fork-like shape1 somewhat as in the modern ,hyracoidea4 ,the ulna and radius in the fore-arm and the tibia and fibula in the lower leg were separate1 but the digits were already reduced to four in each foot4 ,this was one of the few ,santa ,cruz ungulates which possessed a long and heavy tail4 ,the limbs were relatively long and the feet were armed with such slender hoofs that they looked almost like claws4 ,the restoration shows the animal to have had1 like nearly all of the ,typotheria1 a very rodent-like appearance1 a likeness which may1 perhaps1 be unduly increased by the form given to the ears4 ,in the allied genus1 ,interatherium1 from which the family is named1 the head was short1 broad and deep1 almost bullet-like2 the first incisor was enlarged and chisel-shaped1 and the other incisors and the canines were much reduced in size4 ,it is an interesting fact1 observed as yet only in this genus1 but probably true also of all the smaller members of the suborder which had hypsodont teeth1 that the milk-premolars were rooted and comparatively low-crowned1 while their permanent successors were completely hypsodont and rootless4 ,the limbs were considerably shorter than those of ,protypotherium and the tail long and thick1 except for which1 the general appearance of the skeleton suggests that of the modern 8conies0 or 8klipdases0 7,hyracoidea7 of ,africa and ,syria1 a suggestion which ,mr4 ,knight has followed in the drawing 7,fig4 #big1 p4 #fcf74 ,this family was represented in the ,deseado stage by a genus 7,plagiarthrus7 in which the teeth developed roots in old age1 but is not known from more ancient formations4 ,their probable ancestors of the ,eocene were very small animals1 with brachyodont teeth1 the premolars smaller and of simpler pattern than the molars4 ,the upper molars had a continuous external wall1 with indication of separate cusps1 and two transverse crests1 as in the ,toxodonta1 and the lower molars were composed of two incomplete crescents4 ,the teeth were present in undiminished number and the anterior incisors were but little enlarged4 ,nothing is known of the skeleton4 ,,suborder ,,entelonychia4 ,,homalodotheres ,this third suborder of the ,toxodontia was in some respects the most peculiar of all2 no representatives of it have been found in formations later than the ,santa ,cruz1 and the group attained its culmination in the still older ,deseado stage1 in which there were very large members of it4 ,these most extraordinary beasts are still incompletely known1 and little can be done as yet in the way of following out the steps of change which led up to their exceptional characters1 though the suborder itself may be traced back to the ,eocene by means of jaws and teeth alone4 ,the ,santa ,cruz genus labours under the portentous name of ,homalodontotherium1 which may be shortened to the vernacular form of homalodothere4 ,in this genus the dentition was unreduced in number1 and the teeth1 though having rather high crowns1 were all rooted and placed in continuous series1 with a gradual transition in shape from the incisors to the molars4 ,the canines were tusks of very moderate size1 which projected but little above and below the plane of the other teeth2 the premolars1 except the last1 which was nearly molariform1 were smaller and simpler than the molars1 which had a pattern fundamentally the same as in the ,toxodonta4 ,those of the upper jaw were1 however1 less complicated by spurs and accessory crests1 and they had a somewhat stronger resemblance to the rhinoceros pattern1 though the resemblance is demonstrably superficial and not indicative of relationship4 ,the skull was very like that of the ,santa ,cruz toxodonts1 ,nesodon1 etc41 and had the same unusual structure of the auditory region as was found throughout the order1 but differed in many details1 which it is not worth while to enumerate1 though it may be said that the nasal bones were so much shortened that some kind of a proboscis or prehensile upper lip was probably present4 ,the head was quite small in proportion to the size of the animal as a whole4 ,such of the vertebr as are known were quite similar to those of ,nesodon1 but the limbs were far longer and quite stout1 though not massive4 ,the humerus was remarkable for the great development of the ridges for the attachment of the deltoid and supinator muscles and for the prominence of the epicondyles1 all of which gave to the bone the appearance of the humerus of a huge burrower1 yet it is impossible to believe that so large an animal could have had burrowing habits4 ,the fore-arm bones were separate and very long1 the ulna almost as heavy as the radius2 the latter is not known from a complete specimen1 but there would appear to have been some power of rotation1 a power which is conditioned by the shape of the upper end of the radius1 and its mode of articulation with the humerus in the elbow-joint4 ,the thigh-bone was long and heavy and its shaft was much flattened1 having lost the normal cylindrical shape1 but retained a small third trochanter4 ,the bones of the lower leg were separate and relatively short1 and the fibula was uncommonly heavy4 ,so far1 there was nothing very unusual1 save in the shape of the humerus1 about the skeletal structure of the ,entelonychia1 the remarkable characters having been confined to the feet4 ,were it not for these1 the group might be included in the suborder ,toxodonta without difficulty4 ,the feet1 which were five-toed1 differed notably in size1 the manus being more than twice as long as the pes4 ,in the former the metacarpals were very long and1 though actually stout1 were slender in proportion to their length2 there was also a very unusual feature in an ungulate foot1 that the heaviest of the digits was the fifth1 or external one4 ,the mode of articulation of the metacarpals with the first row of phalanges was very exceptional1 indicating an extraordinary mobility of the toes1 and the hoofs had been transformed into large1 bluntly pointed claws1 somewhat like those of the chalicotheres1 those aberrant perissodactyls 7see p4 #ced71 but not so large or so sharp4 ,in the pes1 the ankle-bone had hardly any groove for the tibia1 and its lower end was hemispherical1 as in the ,condylarthra and the clawed mammals generally4 ,the toes were quite grotesquely short in comparison with those of the fore foot1 and1 as in the latter1 the fifth was the heaviest of the series4 ,the hind foot was apparently plantigrade1 the heel-bone and the entire sole being applied to the ground in walking1 while the fore foot was probably digitigrade1 the wrist being raised and the metacarpals vertical4 ,the weight was carried upon the metacarpals and one or more pads under the phalanges1 as in the digitigrade carnivores1 such as dogs and cats4 ,in describing the chalicotheres1 it was pointed out that it was uncertain whether each foot had a single large pad1 or whether there was a separate one under the phalanges of each digit1 and a larger one1 the 8ball of the foot10 under the metacarpals collectively4 ,the same doubt applies to the manus of the homalodotheres4 ,this is the third instance to be cited of the acquisition of claws by a hoofed mammal and1 as in the other two cases1 the chalicotheres and agriochrids 7p4 #chc71 we are confronted by the seemingly incompatible association of teeth which could have masticated only soft vegetable tissues with feet like those of a beast of prey4 ,as in the other two groups1 the problem as to the habits and mode of life of the homalodotheres is an unsolved one1 chiefly because no mammal now living is at all like these extraordinary creatures and one can therefore form but vague conjectures as to the use of such feet to herbivorous animals4 ,possibly they subsisted largely upon roots and tubers and used the great claws for digging up food1 the principal employment that bears now make of their claws4 ,this remarkable transformation of hoofs into claws took place in three unrelated groups of hoofed animals and must have occurred independently among the ,artiodactyla1 the ,perissodactyla and the ,toxodontia4 ,by no possibility1 so far as we are able to comprehend the course of evolutionary change1 could this common characteristic have been due to inheritance from a common ancestry4 ,the homalodotheres were among the largest of ,santa ,cruz mammals1 but they were then already approaching extinction1 while in the ,deseado stage they were more numerous and varied and some of them very much larger4 ,this is an exception to the more common rule1 according to which the successive members of a phylum increased in stature until the maximum was reached and this1 in many cases1 was followed by extinction4 ,the rule is1 however1 by no means without exceptions and several have already been referred to4 ,the largest of ,american proboscideans was the ,imperial ,elephant 7,elephas imperator7 of the upper ,pliocene and ,pleistocene and in many other phyla the ,pleistocene species were much larger than the ,recent4 ,so with the homalodotheres2 they reached their culmination in size and importance in the ,deseado stage1 fewer and smaller forms surviving into the ,santa ,cruz1 after which the entire suborder vanished4 ,the family may be traced back to the ,eocene1 where it is represented chiefly by a genus 7,thomashuxleya7 which had larger canine tusks and much more brachyodont teeth1 but there is no way of determining when the transformation of the hoofs took place4 ,the other two families 7,notostylopid1 ,isotemnid7 flourished chiefly or exclusively in the ,eocene and were small animals still very imperfectly understood4 ,,suborder ,,pyrotheria4 ,,pyrotheres ,this suborder was a remarkable group1 still incompletely known1 of elephant-like animals1 which reached their culmination and died out in the ,oligocene1 their last appearance being in the ,deseado stage4 ,the genus ,pyrotherium from the ,deseado 7also called the ,pyrotherium ,beds7 was the latest1 largest and best known of the suborder4 ,the dentition was much reduced as is shown by the formula3 i #b_/a1 c #j_/j1 p #c_/b1 m #c_/c1 #b #bh4 ,the upper incisors were two downwardly directed tusks1 the first quite small1 the second considerably larger2 the single lower incisor of each side was a stout1 but not very long1 horizontally directed tusk1 with the enamel confined to a longitudinal band2 the other incisors and the canines had disappeared4 ,the premolars1 except the foremost one1 had the molar-pattern1 which very rarely occurred among the indigenous ,south ,american ungulates4 ,the grinding teeth were similar above and below and each had two elevated1 transverse crests1 which1 when quite unworn1 carried a row of bead-like tubercles4 ,these teeth are decidedly reminiscent of the dentition of the aberrant proboscidean ,dinotherium1 from the ,miocene and ,pliocene of ,europe 7p4 #dce71 and this resemblance1 together with the form of the tusks1 has led to the reference of this group to the ,proboscidea1 but the assignment is undoubtedly erroneous1 as is shown by the character of the skull and skeleton4 ,illustration3 ,,fig4 #bdc4--;,head of ,pyrotherium1 showing the two pairs of upper tusks4 ,restored from a skull in the museum of ,amherst ,college4 ,the skull1 hitherto unknown1 was obtained by the ,amherst ,college ,expedition to ,patagonia and its description by ,professor ,f4 ,b4 ,loomis is anxiously awaited4 ,in advance of that1 he has published a brief account1 with a figure4 ,this skull was long and narrow1 with very short facial region and nasal bones so shortened that the nasal canal passed almost vertically down through the head1 as in the elephants1 and there must have been a considerable proboscis4 ,despite this great modification1 the skull was plainly of the toxodont and not of the proboscidean type4 ,the legs were extremely massive and the fore legs were considerably shorter than the hind1 with such a difference in length that the head must have been carried low1 as in the ,pampean ,toxodon4 ,the upper arm and thigh were much longer than the fore-arm and lower leg respectively4 ,the humerus was immensely broadened1 especially the lower end1 and the processes for muscular attachment were extremely prominent4 ,the femur was long1 with broad and flattened shaft1 and had no trace of the third trochanter1 quite strongly resembling the thigh-bone of an elephant1 which1 as we have repeatedly seen1 is the type more or less closely approximated by all of the very heavy ungulates4 ,in the standing position1 the femur was in nearly the same vertical line as the tibia and the whole leg must have been almost perfectly straight1 with the knee-joint free from the body4 ,the short and massive fore-arm bones were cossified1 at least in some individuals1 as were the equally heavy bones of the lower leg1 the fibula being exceptionally stout4 ,little is known of the feet1 but that little renders probable the inference that they were short1 columnar and five-toed4 ,the ,eocene representatives of the ,pyrotheria are known only from very fragmentary material4 ,propyrotherium1 of the ,astraponotus ,beds1 was smaller than the ,deseado genus and still smaller was ,carolozittellia of the ,casa ,mayor1 which was not so large as a tapir4 ,in the latter the molars were of the same type as in the succeeding forms and small tusks had already begun to develop4 ,the older ,eocene genus ,paulogervaisia was probably a member of this suborder2 if so1 it shows that the molars with transverse crests were derived from quadritubercular teeth1 just as happened in the ,proboscidea and several other ungulate groups4 ,,chapter ,,xiii ,,history ,,of ,,the ,,litopterna ,,and ,,astrapotheria ,besides the four well-defined groups which make up the ,toxodontia 7or ,notoungulata7 there are two other extinct orders of indigenous ,south ,american ungulates1 which remain to be considered4 ,these did not have the exceptional development of the auditory region of the skull which characterized the ,toxodontia4 ,the best known and most important genera of the ,litopterna are listed in the following table3 ,,litopterna4 ,litopterns ,i4 ,,macrauchenid4 ,macrauchenia1 ,plioc4 and ,pleist4 ,scalibrinitherium1 ,paran4 ,theosodon1 ,santa ,cruz4 ,cramauchenia1 ,patagonian4 ,protheosodon1 ,deseado4 ,,ii4 ,,proterotheriid4 ,epitherium1 ,monte ,hermoso4 ,diadiaphorus1 ,santa ,cruz and ,paran4 ,proterotherium1 do4 ,thoatherium1 ,santa ,cruz4 ,deuterotherium1 ,deseado4 ,prothoatherium1 do4 ,,iii4 ,,didolodid4 ,didolodus1 ,casa ,mayor4 ,lambdaconus1 do4 ,notoprogonia1 do4 ,proectocion1 do41 etc41 etc4 ,only one of the families of this suborder survived into the ,pampean stage1 where it was represented by a single genus1 ,macrauchenia4 ,like all the other large ,pampean mammals of distinctly ,south ,american type1 this was a grotesque creature1 from the modern point of view4 ,the genus was first discovered by ,darwin1 who says of it3 8,at ,port ,st4 ,julian1 in some red mud capping the gravel on the #ij-;foot plain1 ,i found half the skeleton of the ,macrauchenia ,patachonica1 a remarkable quadruped1 full as large as a camel4 ,it belongs to the same division of the ,pachydermata with the rhinoceros1 tapir1 and palotherium2 but in the structure of the bones of its long neck it shows a clear relation to the camel1 or rather to the guanaco and llama40#ab ,the views upon classification and relationship here expressed have been superseded1 but the passage is an important one in the history of scientific opinion4 ,macrauchenia 7,fig4 #abj1 p4 #baf71 as ,darwin says1 was as large as a camel2 it had an unreduced dentition of #dd teeth and in each jaw the teeth were arranged in continuous series and were quite decidedly hypsodont4 ,both in the upper and the lower jaws the incisors formed a nearly straight transverse row and have a 8mark10 or enamel pit1 like that seen in the horses2 the canines were but little larger than the incisors and did not form tusks4 ,the premolars were smaller and simpler than the molars4 ,the upper molars had two concave and crescentic external cusps1 connected by a median ridge1 as in several families of perissodactyls2 two transverse crests and several accessory spurs and enamel-pockets gave to the grinding surface1 when somewhat worn1 the appearance of considerable complexity4 ,the lower molars had the two crescents1 one behind the other1 which recurred in almost all the ,south ,american types of ungulates2 the vertical pillar which so generally in these types arose in the inner concavity of the posterior crescent was wanting in the permanent teeth of ,macrauchenia1 but present in the milk-premolars4 ,no part of this remarkable animal was more curious than the skull1 which was quite small in proportion to the rest of the skeleton4 ,it was long1 narrow and low1 sloping and tapering forward to a blunt point at the end of the muzzle1 though there was a slight broadening here to accommodate the transverse row of incisors4 ,the sagittal crest was replaced by a short1 narrow and flat area2 the cranium was shortened and the face elongated1 the orbits1 which were completely encircled in bone1 having been shifted behind the line of the teeth1 as in the modern horses4 ,the nasal bones were reduced to a minimum1 a mere vestige of their original length1 the anterior nasal opening being directly over the posterior1 making the nasal passage vertical4 ,such an arrangement is an almost positive proof that in life the animal had a flexible proboscis1 a conclusion which is confirmed by the presence1 on the top of the head and behind the nasal opening1 of deep pits for the attachment of the proboscis-muscles4 ,a very curious feature of this skull was that the bones of the upper jaw1 the maxillaries and premaxillaries of the opposite sides1 united in the median line1 making a long1 solid1 bony rostrum in front of the nasal opening1 a character not found in other land mammals4 ,the neck was almost as long as in a camel and its vertebr agreed with those of the latter in the very exceptional character of having the canal for the vertebral artery passing longitudinally through the neural arch1 instead of perforating the transverse process4 ,as ,darwin says in the passage quoted above1 8it shows a clear relation to the 444 guanaco and llama10 but this is founded on the postulate that such a likeness must1 of necessity1 imply relationship4 ,as was shown in the chapters on the ,artiodactyla and ,perissodactyla1 it is the general rule among long-necked ungulates that the odontoid process of the axis assumes a spout-like shape1 but ,macrauchenia was an exception and had an odontoid which retained its primitive and peg-like shape2 it was1 however1 relatively very short and in cross-section was no longer circular1 but oval4 ,this may be regarded as a step toward the assumption of the spout-like form1 but the extinction of the family put an end to further changes in that direction4 ,the body was rather short and the limbs very long1 giving the animal a stilted appearance1 while the feet were relatively short4 ,the proportionate lengths of the different limb-segments was unusual2 the upper arm was short1 the fore-arm very long1 the thigh long and the lower leg quite short4 ,the humerus was very heavy2 the ulna and radius1 which were firmly cossified1 formed a very long compound bone1 which was broad transversely and thin antero-posteriorly4 ,the long femur had only a small and inconspicuous third trochanter and the shaft was broad and thin1 being flattened1 or 8compressed0 antero-posteriorly4 ,the tibia and fibula were united at both ends2 the former was very heavy at the upper end1 but diminished downward in width and thickness1 and the fibula articulated with the calcaneum1 as in the artiodactyls4 ,the feet were tridactyl and had mesaxonic symmetry2 that is to say1 the median digit1 or third of the original five1 was symmetrical in itself and was bisected by the middle line of the foot1 while the lateral toes 7second and fourth71 each of which was asymmetrical1 formed a symmetrical pair4 ,it is this perissodactyl character of the foot to which ,darwin refers when he says that ,macrauchenia 8belongs to the same division of the ,pachydermata with the rhinoceros1 tapir and palotherium40 ,on the other hand1 the very significant structure of the ankle-joint was radically different from that of the ,perissodactyla2 not only did the calcaneum have a special facet for articulation with the fibula1 but the lower end of the astragalus was a convex 8head10 resting only on the navicular1 as in the ,toxodontia1 ,condylarthra1 ,hyracoidea and other very primitive groups of hoofed animals and in clawed mammals generally4 ,such a combination of characters is not known in any of the perissodactyls and precludes the reference of the ,litopterna to that order1 though such a reference is strongly maintained by several authorities4 ,the ungual phalanges were small and appear to suggest the presence of pads on the feet4 ,the appearance of ,macrauchenia in life must have been sufficiently strange4 ,the small head with its proboscis and the long neck and legs should probably be regarded as indicative of browsing habits1 though the hypsodont teeth show that grazing was at least an occasional mode of feeding4 ,the long limbs and short feet gave to the extremities an appearance unlike that of any existing hoofed animal4 ,the form and size of the ears and the character of the hairy coat are1 of course1 conjectural4 ,in the later ,pliocene the family was represented by forms which differed so little from the ,pampean ,macrauchenia as to call for no particular notice1 but in the presumably lower ,pliocene of the ,paran stage1 occurred several genera1 all unfortunately but imperfectly known1 which are of interest as being less specialized than ,macrauchenia and as showing the way in which some of the peculiarities of the latter were acquired4 ,in ,scalibrinitherium1 which may be taken as an example of these genera1 the teeth were brachyodont2 the upper molars were rather less complex than those of ,macrauchenia1 while the lower molars had the pillar in the concavity of the posterior crescent1 which the ,pampean genus retained only in the milk-teeth4 ,as we have repeatedly found1 the milk-dentition is often conservative and retains primitive or archaic features which have been lost in the permanent teeth1 and ,macrauchenia is another illustration of the same principle4 ,in the skull of ,scalibrinitherium the nasal bones1 though very short1 had not suffered such extreme abbreviation as in the succeeding genus1 the nasal opening was farther forward and the maxillaries united in the superior median line for only a short distance1 while the premaxillaries were fused together for their whole length4 ,the orbit had not been shifted entirely behind the teeth1 but was above the third upper molar4 ,illustration3 ,,fig4 #bdd4--,santa ,cruz macrauchenid 7,theosodon garrettorum7 and predaceous marsupial 7,borhyna tuberata74 ,restored by ,c4 ,knight from skeletons in the museum of ,princeton ,university4 ,next in the ascending series1 to use the genealogist's term1 came the genus ,theosodon of the ,santa ,cruz1 of which almost all the skeletal parts are known and thus make possible a full comparison with ,macrauchenia1 which assuredly was its direct descendant4 ,in view of the great lapse of time involved1 the differences between the two genera were less than might have been expected1 though the more ancient animal was in all respects the more primitive4 ,theosodon was1 in the first place1 considerably smaller1 not much exceeding a llama in size2 the teeth had lower crowns than even those of ,scalibrinitherium and the incisors were arranged in line with the grinding teeth1 not in a transverse row1 but curving inward slightly1 so that those of the opposite sides nearly met in front4 ,the incisors1 canine and first premolar were simple1 sharply pointed1 conical teeth1 which gave an almost reptilian expression to the anterior part of the skull4 ,the upper molars were on the same fundamental plan as those of ,macrauchenia1 but in a less advanced stage of development1 the transverse crests being incomplete and the internal cusps had a certain degree of separateness from the crests and from each other4 ,it is evident that the upper molars were derived from the quadritubercular type4 ,the lower molars had the vertical pillar in the concavity of the posterior crescent very prominently developed4 ,the resemblance of the skull to that of ,macrauchenia is obvious at the first glance1 but it was less specialized and departed less from the ordinary ungulate type4 ,the cranium was longer and the face shorter1 the orbit1 which was incompletely closed behind1 extending over the second molar4 ,there was a sagittal crest1 the length of which differed much in the various species2 the nasal bones were already very short1 though decidedly longer than in the subsequent genus ,scalibrinitherium1 and the anterior nasal opening was extended forward as a long1 narrow slit1 because the maxillaries did not come into contact with each other in the superior median line1 and the premaxillaries touched each other1 but were not cossified4 ,the nasal canal1 though very short1 was horizontal1 not vertical4 ,the skulls of the three genera thus displayed three successive stages in the backward shifting of the orbit and of the anterior nasal opening1 in the shortening of the nasal bones and in the formation of a solid rostrum by the fusion of the upper jaw-bones4 ,no doubt also the living animals exhibited a corresponding gradation in the development of the proboscis4 ,illustration3 ,,fig4 #bde4--;,development of the skull in the ,macrauchenid1 side views4 ,a1 ,theosodon1 ,santa ,cruz4 ,b1 ,scalibrinitherium1 ,paran4 7,after ,ameghino47 ,c1 ,macrauchenia1 ,pampean4 7,after ,burmeister47 n41 nasal bones4 ,illustration3 ,,fig4 #bdf4--;,development of the skull in the ,macrauchenid4 ,a1 ,theosodon4 ,b1 ,scalibrinitherium4 7,after ,ameghino47 ,c1 ,macrauchenia4 7,after ,burmeister47 ,the neck of ,theosodon was even longer proportionately than in ,macrauchenia and the transference of the canal for the vertebral artery from the transverse processes to the neural arch had already taken place1 except in the first1 sixth and seventh vertebr1 and was thus less complete than in the ,pampean genus1 in which all the vertebr of the neck1 save the seventh1 had the canal in its exceptional position4 ,the odontoid process of the axis was less modified than in the latter1 being relatively longer and more conical4 ,the body was rather short1 and the spines of the trunk-vertebr were proportionally higher and more prominent4 ,no caudal vertebr have been found1 but1 from the shape of the sacrum1 it is evident that the tail was short4 ,the limbs were long1 but more slender and less elongate than in ,macrauchenia1 in which the growth of the neck did not keep pace with that of the limbs1 the lengthening of the proboscis probably compensating for this4 ,the shoulder-blade had two conspicuous metacromia1 very much as in the contemporary toxodont1 ,nesodon1 but shorter and more widely separated4 ,the humerus was short and quite slender and the fore-arm bones1 which were much longer1 did not cossify4 ,the femur had a more slender and rounded shaft than in ,macrauchenia and a much larger third trochanter2 the leg-bones were also separate from each other4 ,the tridactyl feet were so like those of the ,pampean genus1 that no particular account of them is necessary1 and the proportions of the limb segments were similar in both genera1 short upper arm and lower leg1 very long fore-arm and thigh1 and short feet4 ,illustration3 ,,fig4 #bdg4 ,left manus of ,theosodon4 ,s41 scaphoid4 ,l41 lunar4 ,py41 pyramidal4 ,tm41 trapezium4 ,td41 trapezoid4 ,m41 magnum4 ,u41 unciform4 ,v41 rudimentary fifth metacarpal4 ,the appearance of the living animal1 as shown in the restoration1 was no doubt somewhat like that of ,macrauchenia1 but less bizarre4 ,that there must have been some sort of a proboscis or prehensile upper lip1 is indicated by the greatly shortened nasal bones1 but this may not have been longer than in the existing ,moose or ,saiga ,antelope4 ,the long neck1 short body and tail and long limbs suggest an animal not unlike a ,guanaco1 but larger and heavier4 ,the hair may or may not have had the woolly character given to it in the drawing2 upon such a point there can be no certainty4 ,in the older formations preceding the ,santa ,cruz1 the macrauchenids are known only from fragmentary material1 though something of their history may be made out even from these fragments4 ,protheosodon1 of the ,deseado stage1 was considerably smaller than the ,santa ,cruz genus and had more primitive upper molars1 in that the internal cusps and intermediate cuspules were isolated and conical1 not forming transverse crests4 ,still smaller were the several genera 7,lambdaconus1 etc47 related to the macrauchenids found in the ,casa ,mayor ,eocene1 which have been referred1 perhaps correctly1 to the ,condylarthra4 ,in these the formation of the external wall of the almost bunodont upper molars was in progress1 by the fore-and-aft extension and transverse thinning of the external cusps2 the internal pair of cusps and the cuspules were separate and conical4 ,with much confidence1 it may be inferred that in these little animals the skull was normal1 the nasal bones were long and that the feet were five-toed1 but demonstration is lacking4 99 99 99 99 99 ,the second family of the ,litopterna1 the ,proterotheriid1 were remarkable for their many deceptive resemblances to the horses4 ,even though those who contend that the ,litopterna should be included in the ,perissodactyla should prove to be in the right1 there can be no doubt that the proterotheres were not closely related to the horses1 but formed a most striking illustration of the independent acquisition of similar characters through parallel or convergent development4 ,the family was not represented in the ,pleistocene1 having died out before that epoch1 and the latest known members of it lived in the upper ,pliocene of ,monte ,hermoso4 ,in the still older ,paran formation more numerous and varied forms occurred1 but only from the ,santa ,cruz have materials been obtained of sufficient completeness to furnish a full account of the structure of these extraordinary animals4 ,not that this remarkable character was due to grotesque proportions2 on the contrary1 they looked far more like the ordinary ungulates of the northern hemisphere than did any of their ,south ,american contemporaries2 it is precisely this resemblance that is so notable4 ,in ,santa ,cruz times the family was represented by a large number of species1 which have been grouped in four or five genera1 which differed sufficiently to require generic separation1 yet were closely similar4 ,in all of them the dental formula was3 i #a_/b1 c #j_/a1 p #d_/d1 m #c_/c1 #b #cf4 ,except in one genus 7,thoatherium7 a pair of small tusks was formed by the enlargement of the second upper and third lower incisors1 as in the toxodonts1 but the first upper and lower and the third upper incisors1 which were retained in the toxodonts1 were lost in this family1 as was also the upper canine1 and the lower canine was very small1 of no functional use4 ,the teeth were brachyodont and1 except the small tusks1 displayed no tendency at any time toward the acquisition of high crowns4 ,the premolars were less complex than the molars1 though the last one approximated the molar-pattern4 ,the upper molars had two crescentic outer cusps1 meeting in a vertical ridge and together forming the outer wall2 the transverse crests were imperfect1 especially the hinder one which was often merely the intermediate cuspule1 and did not fuse with the external wall4 ,the lower molars had the two crescents1 one behind the other1 which recur in the macrauchenids1 all the suborders of the ,toxodontia1 except the ,pyrotheria1 and other ,south ,american ungulates1 but the pillar in the posterior crescent1 which was so characteristic of the groups named1 was reduced to very small proportions and sometimes suppressed altogether4 ,it should be noted1 however1 that this was the loss of an element which was formerly present4 ,the skull had a long cranium and rather short face1 with long1 high sagittal crest4 ,the neck was short1 the odontoid process of the axis peg-shaped1 and the canal for the vertebral artery was in its normal position4 ,the body was rather short1 like that of a deer or antelope2 the number of trunk-vertebr is not definitely known in any of the genera1 but was very probably #ai or #bj1 and the tail must have been short4 ,illustration3 ,,fig4 #bdh4--,skull of ,diadiaphorus1 ,santa ,cruz4 ,american ,museum4 ,the limbs were slender and of moderate length2 there was no cossification between the bones of the fore-arm or the lower leg4 ,the feet were three-toed1 except in one genus 7,thoatherium7 in which they were single-toed1 and nearly or quite the whole weight was carried upon the median digit1 the laterals being mere dew-claws4 ,the shape of the hoofs and the whole appearance of the foot were surprisingly like those of the three-toed horses1 but there were certain structural differences of such great importance as1 in my judgment1 to forbid the reference of these animals1 not merely to the horses1 but even to the perissodactyls4 ,in studying the ,litopterna1 one is continually surprised to note the persistence of archaic and primitive characters in association with a high degree of specialization4 ,illustration3 ,,fig4 #bdi4--,three-toed proterothere 7,diadiaphorus majusculus71 ,santa ,cruz4 ,restored by ,c4 ,knight1 from skeletons in the ,american ,museum and ,princeton ,university4 ,the largest ,santa ,cruz representatives of the family were the species of ,diadiaphorus1 animals considerably taller than a sheep and of heavier build4 ,their appearance was not unlike that of a short-necked1 hornless antelope1 but with the feet of the three-toed horses6 ,these feet were1 however1 merely superficially like those of the horses1 differing in points of fundamental significance4 ,in the horses1 the reduction of the digits was accompanied by a readjustment of the carpal and tarsal articulations1 so that1 in proportion as the median toe was enlarged and the laterals reduced1 the weight was shifted more entirely upon the former4 ,this is the method of digital reduction which ,kowalevsky called 8adaptive0 and is exemplified in all existing artiodactyls and perissodactyls and by none more perfectly than by the monodactyl horses4 ,in 8inadaptive reduction10 the method followed by ,diadiaphorus and the other genera of this family1 there was no readjustment1 or a very imperfect one1 of the articulations1 the lateral digits1 however small and rudimentary1 retaining the connections which they had when they were of full size and function4 ,this distinction may seem to be unimportant1 but its significance is shown by the fact that not a single ungulate with inadaptively reduced feet has survived to the present time4 ,illustration3 ,,fig4 #bej4--,left pes of ,diadiaphorus1 from specimens in ,princeton ,university and the ,american ,museum4 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cn4 #c1 external cuneiform4 ,cb41 cuboid4 ,in still another respect the feet of ,diadiaphorus deviated markedly from those of the horses1 viz4 in the great proportionate length of the phalanges1 especially of the first one1 and the shortness of the metapodials1 the three phalanges of the median digit together exceeding in length the metacarpal or metatarsal1 while in the horses this proportion is reversed4 ,the skull of this genus was short1 deep and with an anterior taper2 it had a long sagittal crest1 but a brain-chamber of good capacity1 considering its geological date4 ,the nasals were quite short1 though the degree of shortening was not such as to suggest the existence of a proboscis4 ,in general appearance the skull recalls that of one of the larger oreodonts 7p4 #cgb7 of the ,north ,american ,oligocene4 ,to the genus ,proterotherium1 the type of the family1 belonged a great number of ,santa ,cruz species1 for at that time the genus was in a state of most vigorous development and the species were so variable that satisfactory discrimination of them is exceedingly difficult4 ,they were all much smaller and slighter animals than the species of ,diadiaphorus1 but did not differ from them in any important structural character4 ,the skull in this genus closely resembled that of the one last named1 save for its smaller size and lighter and more slender proportions2 the nasal bones were considerably longer and the occiput was somewhat wider4 ,illustration3 ,,fig4 #bea4--,skull of ,thoatherium1 ,santa ,cruz4 ,princeton ,university ,museum4 ,a more isolated position was held by the genus ,thoatherium1 which was very clearly demarcated from all of the other genera of the family4 ,its species were the smallest of the commoner ,santa ,cruz members of the order and were of very light and graceful form4 ,the dental formula was the same as in the other genera1 but there were no tusks2 the single upper and two lower incisors were of nearly the same size and simple1 chisel-like form4 ,the upper molars had the same elements as in the preceding genera1 but somewhat differently connected1 the two internal cusps and the anterior intermediate cuspule being united into a nearly longitudinal ridge4 ,the skull was light1 slender and pointed2 the nasals were shortened1 though less than in ,diadiaphorus2 the sagittal crest was shorter than in the latter and the occiput was far narrower4 ,the neck was short1 the body of moderate length and the tail short4 ,the limbs and especially the feet were proportionately more elongate and slender than in any other known genus of the family1 giving quite a stilted appearance to the skeleton4 ,the fore-arm bones were not cossified1 but the ulna was much more reduced than in any of the other genera of the family1 and the same is true of the fibula1 which1 though very slender1 showed no tendency to unite with the tibia4 ,the limb-bones1 especially the femur1 had a decided resemblance to those of ,mesohippus1 the lower ,oligocene tridactyl horse of ,north ,america1 with the smaller species of which1 ,m4 bairdi1 ,thoatherium agreed well in size4 ,most remarkable of all were the feet1 which were more strictly monodactyl than those of any other known mammal4 ,the single functional digit1 the third1 had on each side of its upper end a very small1 scale-like nodule of bone1 the last vestiges of the lateral digits1 corresponding to the immensely larger splints of the horse4 ,despite the unrivalled completeness of digital reduction which ,thoatherium displayed1 the mode of reduction was inadaptive and the rudimentary metapodials retained the same carpal and tarsal connections that they originally had in the pentadactyl manus1 a very great difference from the horses4 ,the ankle-joint also was of the same primitive character as in the other ,litopterna4 ,the feet were relatively longer and more slender than in the other proterotheres and the metapodial of the single functional digit longer in proportion to the phalanges4 ,illustration3 ,,fig4 #beb4--,single-toed proterothere 7,thoatherium minusculum71 ,santa ,cruz4 ,restored by ,c4 ,knight from a skeleton in the museum of ,princeton ,university4 ,the appearance of the living animal1 aside from the character of the hair1 colour-pattern1 etc41 may be closely inferred from the skeleton4 ,it was a much smaller and more graceful animal than its contemporary and relative ,diadiaphorus1 as light and agile as a gazelle4 ,the head had some resemblance to that of a small horse1 but the neck was much shorter than in the horses2 the body also was shorter than in the latter1 and the proportions of the trunk and limbs were quite as in the smaller antelopes4 ,but these likenesses to horses and antelopes were1 it must again be emphasized1 superficial2 the fundamental characteristics of structure were more primitive than in the most ancient known artiodactyls and perissodactyls4 ,illustration3 ,,fig4 #bec4--,left pes of ,thoatherium4 ,princeton ,university ,museum4 ,letters as in ,fig4 #bej4 ,with the aid of the fragmentary material which alone represents the proterotheres in the formations preceding and following the ,santa ,cruz in time1 it is not practicable to trace the development of the various phyla in a satisfactory manner4 ,two of the ,santa ,cruz genera1 ,diadiaphorus and ,proterotherium1 continued into the lower ,pliocene 7,paran71 and two additional ones have been named1 but little is known about them4 ,the latest known member of the family so far discovered is a genus 7,epitherium7 from the upper ,pliocene of ,monte ,hermoso1 a tridactyl form like ,diadiaphorus4 ,it is a noteworthy fact that the most advanced and specialized genus of the entire family ended with the ,santa ,cruz1 while the less differentiated types survived till a considerably later period4 ,possibly1 it was the incoming of the highly efficient ,carnivora from ,north ,america that led to the extermination of the last proterotheres4 ,turning backward from the ,santa ,cruz1 the family may be traced without any question to the ,deseado stage of the ,oligocene1 though nothing but teeth has yet been obtained1 while in the ,eocene it would appear to have become merged in the same group of small1 ,condylarthra-like animals with quadritubercular molars1 as those which are regarded as the probable ancestors of the macrauchenids4 ,however likely this conclusion may seem to be1 its confirmation must await the discovery of much more complete specimens than are now available4 ,,order ,,astrapotheria4 ,,astrapotheres ,in the ,santa ,cruz another group of peculiar ,south ,american ungulates1 the ,astrapotheria1 made its last recorded appearance4 ,though not at all uncommon in that formation1 no complete or even partial skeleton has yet been found1 but merely the skull and a few bones of the limbs and feet4 ,for this reason there is much doubt as to the systematic position and relationships of these animals1 which were among the most curious of the many strange mammals which made up the ,santa ,cruz fauna4 ,they were mentioned in connection with the ,amblypoda 7p4 #def7 as possible representatives of that order in ,south ,america1 but1 as will be seen later1 this is an improbable conclusion1 and the group appears to have been indigenous in the southern continent1 in which1 at all events1 it had a very long history4 ,it has not been found in any formation later than the ,santa ,cruz1 unless the ,friasian fauna1 which contains it1 should be removed from that stage1 of which it apparently forms the latest division4 ,i4 ,,astrapotheriid4 ,astrapotherium1 ,santa ,cruz and ,patagonian4 ,astrapothericulus1 ,patagonian4 ,parastrapotherium1 ,deseado4 ,astraponotus1 ,astraponotus ,beds4 ,albertogaudrya1 ,casa ,mayor4 ,,ii4 ,,trigonostylopid4 ,trigonostylops1 ,casa ,mayor4 ,edvardocopeia1 ,astraponotus ,beds4 ,the genus ,astrapotherium1 which was the only well-defined representative of its family and order in the ,santa ,cruz stage1 contained several species1 some of them the largest animals of their time1 as well as the most grotesque in appearance4 ,the dentition differed in some important respects from that of all the other ,south ,american ungulates1 the formula being3 i #j_/c1 c #a_/a1 p #b_/a1 m #c_/c1 #b #bh4 ,the upper incisors had completely disappeared1 but the lower ones were large and1 what was an exceptional character1 they were partially divided into two lobes1 somewhat as in the ,eocene uintatheres of ,north ,america 7p4 #ddf74 ,the canines were very large and formidable tusks1 which grew throughout life and apparently formed no root2 the upper tusk was nearly straight and was obliquely truncated by the strongly curved and sharp-pointed lower tusk4 ,this arrangement was very unusual among ,south ,american hoofed mammals1 many of which had no tusks at all2 and in those which possessed them1 such as the toxodonts 7p4 #dfh71 they were mostly incisors4 ,only in the astrapotheres and homalodotheres were there canine tusks1 and in the latter group they were small and of limited growth4 ,all the teeth1 except the canines1 were brachyodont and1 though rather high-crowned1 formed roots before coming into use4 ,the premolars were small and greatly reduced in number 7#b_/a71 and in pattern were simpler than the molars4 ,the upper molars were constructed on essentially the same plan as in the ,toxodonta2 indeed1 the first specimen of this genus collected was referred to a large species of ,nesodon by ,owen4 ,on the other hand1 the resemblance to the rhinoceros teeth is very decided1 and has led several writers to postulate a relationship between the astrapotheres and the rhinoceroses4 ,the lower molars were of the bicrescentic pattern so frequently met with already2 these teeth were very narrow in proportion to their length and strongly suggest those of ,metamynodon1 the supposedly aquatic rhinoceros of the ,north ,american ,oligocene 7p4 #cdf74 ,it may be confidently inferred that so small a number of premolars was due to reduction from a full series1 and this is confirmed by the milk-dentition1 in which the premolars were #d_/c4 ,illustration3 ,,fig4 #bed4--;,head of ,astrapotherium magnum4 ,santa ,cruz4 ,restored from a skull in the museum of ,princeton ,university4 ,the skull was extremely peculiar1 more so than in any other of the contemporary genera of hoofed animals4 ,the toothless premaxillaries were quite small1 but thick1 and must have supported an elastic pad1 against which the lower incisors could effectively bite in cropping herbage4 ,the nasal bones were extremely short and there must have been a proboscis or greatly inflated snout1 probably the former2 the immense development of sinuses in the frontal bones elevated the whole forehead into a great1 dome-like convexity1 a feature which is not equalled in any other known mammal4 ,the orbits were open behind and the brain chamber was small1 so that the sagittal and occipital crests were very high and strong1 to afford sufficient surface for the attachment of the great temporal muscles4 ,the horizontal portion of the lower jaw was shallow vertically1 but very thick and massive1 and the symphyseal region was broad and depressed4 ,unfortunately1 the skeleton is still very incompletely known4 ,of the vertebr1 only the atlas and axis have been recovered1 and these resembled those of the ,santa ,cruz toxodont ,nesodon1 on a larger scale4 ,the scapula had a very thick spine1 without the projections which were found in most of the ,santa ,cruz ungulates4 ,the limb-bones were long and comparatively slender1 and the processes for muscular attachment were singularly small and weak2 the bones of the fore-arm and lower leg did not cossify and were proportionately elongate1 the tibia being but little shorter than the femur4 ,the latter had the flattened shaft which recurs in nearly all of the very heavy ungulates1 but retained a remnant of the third trochanter4 ,if the feet found isolated in the ,santa ,cruz and ,deseado stages have been correctly referred to this order1 then the genus was five-toed and the feet were broad1 short and heavy1 quite elephantine in appearance1 especially the fore foot4 ,the ankle-joint was very peculiar and the calcaneum had no articulation with the fibula1 which it had in all the other indigenous ,south ,american ungulates4 ,incomplete as the material is1 it is yet possible to form some general conception of this extraordinary animal when in life4 ,the head was short1 broad and deep1 rounded and very probably furnished with a proboscis2 the neck was of moderate length1 so that the mouth could not reach the ground without a straddling of the fore legs4 ,the body was no doubt long1 the limbs long and rather slender1 giving the animal a stilted appearance1 the feet very short1 broad and columnar4 ,several species of the genus are known1 which differed much in size1 the largest 7,a4 giganteum7 probably exceeding any modern rhinoceros in height and length1 and the smallest 7,a4 nanum7 not much larger than a ,wild ,boar4 ,astrapothericulus1 of the ,patagonian stage1 was smaller than the average species of the ,santa ,cruz genus1 and had teeth of the same number1 but the canines were not capable of indefinite growth1 and the lower molars had the pillar in the posterior crescent so characteristic of the ,south ,american hoofed animals4 ,in the ,deseado stage1 on the contrary1 the astrapotheres were of larger size1 and in the commonest genus1 ,parastrapotherium1 the grinding teeth had lower crowns and the premolars were more numerous1 at least #c_/b4 ,in the still more ancient ,astraponotus1 which gives its name to the upper ,eocene 7or lower ,oligocene7 of ,patagonia1 the premolars were present in full series4 ,in the ,casa ,mayor the order was abundantly represented by still more primitive genera1 which assuredly had an undiminished number of teeth1 though this has not been proved4 ,one of these genera1 ,albertogaudrya1 was the largest animal of its time and the highly probable ancestor of the series leading to the ,santa ,cruz ,astrapotherium4 ,the second family of the order1 the ,trigonostylopid1 did not survive beyond the ,eocene and is so imperfectly known that any account of it would be to small profit4 ,as stated above1 the ,astrapotheria were an isolated group and their relationships are problematical and are likely to remain so pending the discovery of much more complete specimens of the various genera which made up the series4 ,i am inclined to the opinion1 however1 that all of the indigenous groups of ,south ,american ungulates1 which inhabited that continent before the great immigration from the north1 were derivatives of the same stock and more nearly related to one another than to any of the orders which lived in other regions4 99 99 99 99 99 ,in looking over the labyrinth of ungulate history1 as recorded by the fossils1 certain facts stand out clearly1 while others are still very obscure4 ,it is like trying to trace the plan of vast and complicated ruins1 which here are deeply buried in their own dbris1 there are fully exposed and in another place are swept away so completely that hardly a trace remains4 ,but the problem is far more complex than any which can be presented by buildings1 for the factor of repeated migrations from continent to continent comes in to obscure the evidence4 ,had each of the great land areas received its original stock of early mammals and then been shut off from communication with any other1 many of the difficulties would be removed1 but the story would lose half its interest4 ,within the limits of the family1 giving to that group the broad and elastic definition which has hitherto been employed1 we have repeatedly found it feasible to construct a phylogenetic series which very nearly represents the steps of structural modification as they occurred in time4 ,much less frequently is it possible to trace allied families to their common starting point1 and1 so far as the hoofed animals are concerned1 in no case have we yet succeeded in doing this for the separate orders4 ,the obstacle lies in the fact that the ordinal groups were already distinct1 when they made their first appearance in the known and accessible records1 and the hypothetical ancestors common to them all1 or to any two of them1 are to be sought in regions of which we know little or nothing4 ,nevertheless1 certain legitimate inferences may be drawn from the available evidence4 ,it remains to be proved whether the assemblage of hoofed mammals1 as a whole1 was of single or multiple origin4 ,have all ungulates been derived from a common stock1 or did they arise independently from several groups of clawed mammals8 ,while the records cannot be followed back to the point1 or points1 of origin of the various orders1 yet it is a noteworthy fact that1 between several of them1 the differences grow less marked as the more ancient members are reached1 as though they were converging to a common term2 others again show little such approximation1 and the most probable conclusion from the evidence now at hand is that the ungulate assemblage is composed of several independent series4 ,one such series is that of the ,hyracoidea and ,proboscidea1 to which ,dr4 ,schlosser has given the name 8,subungulata10 and has pointed out its relationship to the ,condylarthra1 which1 however1 is not a close one and may be illusory4 ,another apparently natural group is that of the peculiarly ,south ,american forms1 the ,toxodontia1 with its four suborders1 the ,litopterna and the ,astrapotheria1 which all appear to be traceable to closely allied families in the ,eocene1 whose teeth strongly suggest derivation from the ,condylarthra2 but the material does not permit any positive statements4 ,the ,artiodactyla and ,perissodactyla have so many similarities that they have always been regarded as closely related groups1 but the distinction between them was almost as sharply drawn in their most ancient known members as it is to-day1 and there was no distinct tendency to converge back into a common stem4 ,their mutual relationships are thus obscure1 but the ,perissodactyla1 at least1 seem to be derivable from a condylarthrous ancestry4 ,the ,condylarthra1 as a whole1 were by far the most primitive of the ungulates1 which they connected with the clawed mammals4 ,none of the genera yet discovered can be regarded as ancestral to any of the higher orders1 but it is entirely possible that in the upper ,cretaceous period the ,condylarthra were spread over all the continents1 except ,australia1 and that from them the other ungulate orders arose in different regions4 ,at all events1 the ,condylarthra show how the transition from clawed to hoofed types may have occurred and perhaps actually did so1 but it would be premature to affirm this4 ,,chapter ,,xiv ,,history ,,of ,,the ,,carnivora ,the story of the hoofed mammals1 as sketched in brief outline in the preceding chapters 7,,viii-,,xiii71 is a curious mixture of relatively full and satisfactory paragraphs1 with scanty1 broken and unintelligible ones1 not to mention those which have not yet been brought to light at all4 ,with all its gaps and defects1 which inhere in the nature of things1 the history of the various ungulate series is the best that the palontology of mammals has to offer and constitutes a very strong and solid argument for the theory of evolution4 ,for the ,carnivora the story is less complete and for obvious reasons4 ,individual abundance was a very large factor in determining the chances of preservation in the fossil state for any given species1 and1 as a rule1 whole skeletons are found only when the species was fossilized in large numbers4 ,in any region the ,carnivora are less numerous than the herbivora upon which they prey1 and while most ungulates live in larger or smaller herds1 the carnivores are mostly solitary4 ,the ,carnivora are divisible into three well-marked suborders1 called respectively the ,pinnipedia1 ,fissipedia and ,creodonta4 ,the ,pinnipedia1 seals1 walruses1 etc41 which are almost purely marine in habitat1 are not dealt with in this book1 since so little can be learned of them from the fossils1 and the ,creodonta1 an extremely ancient and primitive group1 will be treated separately4 ,the ,fissipedia are chiefly terrestrial1 though they include the otters1 and their subdivisions1 so far as the ,american forms are concerned1 are shown in the following table1 which1 it should be observed1 omits several genera4 ,unless otherwise noted1 the genera are ,north ,american4 ,suborder ,,fissipedia4 ,land ,carnivora ,i4 ,,canid1 ,dogs1 ,wolves1 ,foxes1 etc4 ,canis1 ,wolves1 ,pleist4 and ,rec4 ,vulpes1 ,red ,fox1 do4 ,urocyon1 ,grey ,fox1 do4 ,cerdocyon1 fox-like wolves1 ,s4 ,a41 do4 ,icticyon1 ,bush-,dog1 ,s4 ,a41 do4 8,cyon1 ,dhole1 mid4 and up4 ,mioc4 ,dinocynops1 ,s4 ,a41 ,pleist4 lurodon1 up4 ,mioc4 and low4 ,plioc4 ,tephrocyon1 mid4 ,mioc4 to low4 ,plioc4 ,borophagus1 up4 ,mioc4 to mid4 ,plioc4 ,ischyrocyon1 up4 ,mioc4 ,amphicyon1 mid4 ,mioc4 to low4 ,plioc4 ,daphnodon1 low4 ,mioc4 ,enhydrocyon1 up4 ,oligo4 ,temnocyon1 up4 ,oligo4 ,mesocyon1 up4 ,oligo4 ,cynodesmus1 low4 ,mioc4 ,daphnus1 ,oligo4 ,cynodictis1 ,oligo4 ,procynodictis1 up4 ,eoc4 ,,ii4 ,,procyonid1 ,raccoons1 etc4 ,procyon1 ,raccoons1 ,n4 and ,s4 ,a41 ,pleist4 and ,rec4 ,nasua1 ,coatis1 ,s4 ,a41 ,pleist4 and ,rec41 now extending to ,calif4 ,cyonasua1 ,s4 ,a41 up4 ,plioc4 ,bassariscus1 ,cacomistle1 low4 ,plioc4 to ,rec4 ,phlaocyon1 low4 ,mioc4 ,leptarctus1 up4 ,mioc4 ,potos1 ,kinkajou1 ,neotropical1 ,recent4 ,,iii4 ,,ursid1 ,bears4 ,ursus1 true ,bears1 ,pleist4 and ,rec4 ,tremarctos1 ,spectacled ,bear1 ,s4 ,a4 ,arctotherium1 ,short-faced ,bears1 ,n4 and ,s4 ,a41 ,pleist4 ,,iv4 ,,mustelid1 ,martens1 ,weasels1 etc4 ,mustela1 ,weasels1 mid4 ,mioc4 to ,rec4 ,grison1 ,grisn1 ,s4 ,a41 ,pleist4 to ,rec4 ,tayra1 ,tayra1 do4 ,martes1 ,martens1 up4 ,mioc4 to ,rec4 ,gulo1 ,wolverene1 ,pleist4 and ,rec4 ,canimartes1 mid4 ,plioc4 ,brachypsalis1 up4 ,mioc4 ,megalictis1 low4 ,mioc4 lurocyon1 do4 ,oligobunis1 up4 ,oligo4 and low4 ,mioc4 ,bunlurus1 low4 ,oligo4 ,mephitis1 ,skunk1 ,pleist4 and ,rec4 ,spilogale1 ,spotted ,skunk1 do4 ,conepatus1 ,s4 ,a4 ,skunk1 ,pleist4 and ,rec41 ,n4 ,a41 ,rec4 ,taxidea1 ,badger1 ,pleist4 and ,rec4 ,lutra1 ,otters1 up4 ,mioc4 to ,rec41 ,s4 ,a41 ,pleist4 and ,rec4 ,latax1 ,sea-,otter4 ,v4 ,,felid4 ,cats4 ,felis1 true ,cats1 ,n4 ,a41 low4 ,plioc4 to ,rec41 ,s4 ,a41 ,pleist4 and ,rec4 ,lynx1 ,lynx1 ,pleist4 and ,rec4 ,pseudlurus1 mid4 and up4 ,mioc4 ,smilodon1 ,sabre-tooth ,tiger1 ,n4 and ,s4 ,a41 ,pleist4 8,machairodus1 mid4 ,mioc4 to ,plioc4 ,nimravus1 up4 ,oligo4 ,archlurus1 do4 ,hoplophoneus1 ,oligo4 ,dinictis1 do4 ,eusmilus1 low4 ,oligo4 ,two families1 the hyenas 7,hynid7 and civet-cats 7,viverrid71 are omitted from the table because they apparently never reached the western hemisphere4 ,the bears1 of ,old ,world origin1 invaded ,america at a very late period and are not certainly known here before the ,pleistocene4 ,the other four families were well represented in ,north ,american history1 though the great weasel tribe 7,mustelid7 went through the greater part of its history in the ,old ,world4 ,none of the families is indigenous in ,south ,america1 and all of the five families which it now shares with ,north ,america came in in the series of immigrations1 of which the first recorded effects are found in the ,pliocene and continued into the ,pleistocene4 ,the ,fissipedia are adapted to a great variety of habits and modes of life and consequently there is considerable diversity of structure among them1 though they all form a homogeneous1 natural group4 ,the dogs 7,canid7 are terrestrial1 neither swimmers nor climbers2 some1 like the foxes1 are solitary1 others1 like the wolves1 hunt in packs and nearly all are strong1 swift runners4 ,the cats 7,felid7 which have a remarkable range of size1 are terrestrial or arboreal2 they take their prey by stalking and leaping upon it1 not by running it down4 ,the bears 7,ursid7 are mostly omnivorous1 not very often killing prey1 and largely vegetarian in diet4 ,the raccoons 7,procyonid7 are chiefly arboreal and omnivorous4 ,the very large and varied weasel family 7,mustelid7 have different habits1 though nearly all are fierce and bloodthirsty4 ,otters and sea-otters are aquatic and prey chiefly on fish2 minks and fishers are semi-aquatic2 martens are arboreal1 skunks terrestrial and badgers fossorial4 ,while there is thus much diversity of habit with corresponding differences of structure among the ,fissipedia1 there is a certain unity of plan recognizable among them all4 ,with but few exceptions1 the incisors are present in full number and the canines are formidable lacerating weapons4 ,especially characteristic of the dentition are the 8sectorial0 or 8carnassial0 teeth1 always the fourth upper premolar and first lower molar1 which form a pair of shearing blades1 the premolar biting outside4 ,in the bears and most of the raccoons the teeth are tuberculated1 in adaptation to the omnivorous habit1 and the carnassials have lost the shearing form1 though clearly derived from that type4 ,the skull has powerful jaws1 and the crests and ridges for the attachment of the jaw muscles are prominent except in very small animals1 and the stout1 boldly outcurving zygomatic arches are very characteristic4 ,the face may be elongate1 as in the dogs1 or extremely short1 as in the cats1 or of intermediate length2 the brain-case is relatively capacious1 and the orbits1 except in the cats1 are widely open behind4 ,the neck is never very long1 but the body often is1 and the tail varies greatly in length1 as do also the limbs4 ,there is great difference1 too1 between the various families in the prominence of the processes on the limb-bones for the attachment of muscles1 as expressive of the muscular development of the limbs1 and also in the extent to which the fore foot can be rotated and used for grasping4 ,in all existing ,fissipedia the femur has no third trochanter1 but many extinct genera possessed it4 ,the bones of the fore-arm and lower leg are always separate and uninterrupted4 ,in the wrist 7carpus7 there is always a large bone1 the scapho-lunar1 which is made up by the coalescence of three elements1 the scaphoid1 lunar and central1 a feature which1 though recurring in a few other mammals1 is essentially characteristic of the modern ,carnivora4 ,the feet are armed with claws more or less sharp1 which in some families1 notably the cats1 are retractile and may be folded back into the foot4 ,the gait may be plantigrade1 as in the raccoons and bears1 or digitigrade1 as in the dogs and cats1 or intermediate in character4 ,throughout the ,paleocene and most of the ,eocene1 there were no ,fissipedia1 the flesh-eaters all belonging to the extinct ,creodonta1 and the first clearly recognizable fissipedes occurred in the upper ,eocene or ,uinta4 #a4 ,canid4 ,dogs1 ,wolves1 ,foxes1 etc4 ,this family1 which may with convenience be called simply dogs1 is at present the most widely distributed of the families of ,fissipedia1 occurring in every continent1 even ,australia1 and ranging through all climates almost from pole to pole4 ,they are a singularly homogeneous family and show few differences of structure2 such differences as there are affect chiefly the number and size of the teeth and external characters1 such as the size of the ears1 length and colouring of the hair1 etc4 ,the many domestic breeds are not here considered4 ,almost alone among the ,fissipedia the dogs capture their prey by running it down1 and they are endowed with remarkable speed and endurance4 ,the entire organism1 especially the limbs and feet1 are adapted to cursorial habits4 ,for the purpose of comparison with the extinct genera of the family1 some account of a wolf will suffice4 ,the wolves1 like most other members of the family1 have a larger number of teeth than is usual in the suborder1 as appears from the formula3 i #c_/c1 c #a_/a1 p #d_/d1 m #c_/c1 #b #db1 that is to say1 only the third upper molar has been lost from the typical number1 though the third lower is very small and seemingly on the point of disappearance 7,fig4 #dd1 p4 #ic74 ,the upper sectorial tooth1 the fourth premolar1 has its shearing blade made up of two sharp-edged cusps1 one behind the other1 and there is a small internal cusp carried on a separate root2 the upper molars are triangular and tritubercular and are used for crushing4 ,the lower sectorial1 the first molar1 has an anterior blade of two shearing cusps1 with the remnant of a third1 and a low1 basin-like posterior 8heel40 ,the skull is characterized by the long face and jaws and by the structure of the auditory region2 the tympanic bones are inflated into large oval bull1 which are hollow and undivided1 and the external opening of each is an irregular hole1 without tubular prolongation4 ,there is an alisphenoid canal for the passage of the internal carotid artery4 ,the neck1 body and tail are of moderate length and the vertebr of the loins are not conspicuously large and heavy4 ,there is no collar-bone4 ,the limb-bones have a distinct1 though superficial1 resemblance to those of hoofed animals2 the humerus has no very prominent ridges for the attachment of muscles and no epicondylar foramen1 and the femur no third trochanter4 ,the fore-arm bones are separate1 but are so articulated together and with the humerus as to give the fore foot no power of rotation4 ,the manus in all existing wild species has five digits1 though the pollex or first digit is very small1 a mere dew-claw2 the four functional digits are arranged in two symmetrical pairs1 very much as in the artiodactyls1 a longer median pair1 of which the metacarpals have a nearly square cross-section1 and a shorter lateral pair 7#b;d and #eth7 of more trihedral form4 ,all the metacarpals are closely appressed and almost parallel4 ,the pes has four digits arranged in similar fashion4 ,the claws are blunt and non-retractile1 and are of little use in seizing or lacerating prey1 but are useful in digging4 ,the ungual phalanges have no bony hoods reflected over the base of the claw4 ,all modern forms are digitigrade4 ,materials are lacking for the construction of any such detailed phylogeny of the dogs as has been accomplished for many ungulates4 ,many of the extinct genera are known only from skulls1 or even jaws1 and the well-preserved skulls are too few to form distinctly defined and continuous series4 ,on the other hand1 there is every reason to believe that the canine genera of the successive geological stages did approximately represent the successive steps of development within the family1 though it is difficult to distinguish between the phyla4 ,the ,pleistocene dogs1 for the most part1 differed little from the ,recent ones2 there were some very large species like the ,canis dirus 7,frontispiece7 of the ,mississippi ,valley and the ,pacific ,coast4 ,two very peculiar genera have been reported4 ,one 7,pachycyon71 from a cave in ,virginia1 had remarkably short1 stout and strongly curved limb-bones1 which suggest otter-like habits2 the other 7,hynognathus71 from ,california1 had a very short face and extremely massive lower jaw and very heavy teeth2 it was probably like a hyena in appearance4 ,illustration3 ,,fig4 #bee4--,skull of ,cynodesmus thoides1 a lower ,miocene wolf4 ,princeton ,university ,museum4 ,compare with ,fig4 #g1 p4 #fb4 ,as far back as the ,blanco stage of the middle ,pliocene1 remains occur which are assigned to the modern genus ,canis1 though better preserved specimens would probably require their removal from that genus4 ,in the lower ,pliocene the phylum of the true wolves was represented by ,tephrocyon1 which1 so far as it is known1 differed only in minor details from ,canis1 and ,tephrocyon went back to the middle ,miocene4 ,what would appear to be its direct ancestor is ,cynodesmus1 of the lower ,miocene1 which1 in view of the long lapse of time involved1 differed less from the modern wolves than one would have supposed1 but the differences are significant1 as pointing back to a far more primitive type of structure4 ,cynodesmus was a small animal1 intermediate in size between a ,red ,fox and a ,coyote4 ,the dental formula was the same as in ,canis1 but the teeth were relatively smaller and more closely crowded1 as the face and jaws were shorter and the cranium1 though longer1 had a less capacious brain-chamber4 ,the cast of this chamber1 which very perfectly reproduces the form of the brain1 shows that the latter was not only smaller but less convoluted than in the modern animals1 and this1 in turn1 denotes a lower grade of intelligence4 ,the limb-bones were like those of wolves1 but the feet were quite different4 ,in the manus the first digit1 or pollex1 was much less reduced1 though considerably shorter than the other digits1 which were not in two symmetrical pairs1 but were all of different lengths1 not closely appressed1 but arranged in radiating fashion2 the metacarpals had not yet acquired the quadrate or trihedral form1 but were more oval in cross-section4 ,the pes was more modernized1 but had five digits1 which is not true of any existing member of the family4 ,the claws were thin and sharp and were slightly retractile1 a power which has been completely lost in all the modern canids4 ,such an animal could hardly have been preminently cursorial4 ,illustration3 ,,fig4 #bef4--,skull of primitive 8bear-dog0 7,daphnus felinus74 ,white ,river stage4 7,after ,hatcher47 ,out of the crowd of dog-like creatures in the ,john ,day ,oligocene1 it is not yet practicable to select one which is to be taken as the ancestor of the ,recent wolves through ,cynodesmus1 nor can this be done with better assurance of success in the ,white ,river1 though the beginning 7,daphnus7 of the bear-dogs in that formation probably closely represents the ancestral stage sought for4 ,it is likely that several of the phyla into which the family was divided became blended in a common stock at that stage4 ,illustration3 ,,fig4 #beg4--,upper teeth of ,daphnus felinus4 p4 #d fourth premolar4 7,after ,hatcher47 ,illustration3 ,,fig4 #beh4--,right manus of ,daphnus felinus4 ,sl41 scapho-lunar4 ,py41 pyramidal4 ,ps41 pisiform4 ,u41 unciform4 7,after ,hatcher47 ,compare with ,fig4 #cb1 p4 #hb4 ,a second phylum1 now entirely extinct1 is that of the bear-dogs1 which is not certainly recorded later than the middle ,pliocene1 though some have been doubtfully reported from the older ,pleistocene of the ,great ,plains and the remarkable ,californian genus1 ,hynognathus1 may have been an offshoot of the same stock4 ,the phylum was characterized by the unusually large size of the molars and by certain other features1 which1 however1 are not known to have persisted through the entire series from first to last4 ,in the middle ,pliocene lived some very large bear-dogs1 of the genus ,borophagus1 the teeth of which had a strong likeness to those of the hyenas and probably the animals had hyena-like habits1 feeding largely upon carrion and crushing the stoutest bones with their massive teeth4 ,the same1 or a very similar1 genus lived in the lower ,pliocene1 but none of the species of that date is at all well known4 ,in the upper ,miocene occurred several species which have been referred to the ,european genera1 ,amphicyon and ,dinocyon4 ,the latter was an enormous canid1 equalling in size the largest of living bears1 the great ,kadiak ,bear of ,alaska1 and1 though probably having a long and heavy tail1 was much like a bear in appearance4 ,the teeth indicate a more exclusively carnivorous habit than that of the bears and these may well have been savage and terrible beasts of prey4 ,illustration3 ,,fig4 #bei4--,lower ,miocene 8bear-dog0 7,daphnodon superbus74 ,restored from a skeleton in the ,carnegie ,museum1 ,pittsburgh4 ,amphicyon1 which had three upper molars1 continued down through the middle ,miocene1 but was replaced in the lower by ,daphnodon1 which may or may not have been its direct ancestor4 ,the uncertainty as to the exact relationship between the two genera will remain until more complete material shall have been obtained from the middle ,miocene4 ,daphnodon was the largest dog of its time1 the contemporary wolves 7,cynodesmus7 having been hardly half so large1 but was much inferior in size to the huge bear-dogs of the middle and upper ,miocene4 ,the skull resembled that of a large wolf1 but the tympanic bull were smaller and more loosely attached and the molar teeth were relatively much larger1 a persistent characteristic of this phylum4 ,the very long and heavy tail was a cat-like feature4 ,the limbs were comparatively short and stout2 the humerus had the epicondylar foramen and the femur retained a trace of the third trochanter1 both of which are lost in the modern members of the family4 ,the feet were not at all canine in type1 but rather resembled those of the ancient and unspecialized flesh-eaters4 ,there were five digits in manus and pes and were not arranged in parallel pairs1 but diverging2 the metapodials were of oval cross-section1 not squared1 and their lower ends1 which articulated with the first row of phalanges1 had hemispherical surfaces1 not semicylindrical4 ,the claws were sharp and a remnant of former retractility was to be observed4 ,such an animal could hardly have been a strong and enduring runner and its structure suggests that it captured its prey by stalking and leaping upon it4 ,the wolf-like head1 with cat-like body1 tail and limbs1 made a strange combination1 not closely paralleled by any existing carnivore4 ,through the ,oligocene the phylum was carried back by the several species of ,daphnus1 assuredly the ancestor of ,daphnodon and decidedly more primitive in many respects4 ,the ,oligocene genus was a much smaller animal than its lower ,miocene successor1 the larger species hardly equalling a ,coyote2 the teeth were smaller and more closely set1 but the molars were proportionately large1 while the carnassials were less finished and effective shearing blades4 ,the skull was less distinctively dog-like and had a smaller brain-case1 with very prominent sagittal and occipital crests1 a longer cranium and shorter face2 the tympanic bones were very small and so loosely attached to the skull that they are rarely found1 a very striking difference from all existing dogs4 ,the backbone was remarkable for the unusually large size of the lumbar vertebr1 a point of resemblance to the cats and suggesting that ,daphnus had great powers of leaping2 there was a long1 heavy1 leopard-like tail1 and the caudal vertebr were very like those of the long-tailed cats4 ,the limbs and feet were similar in character and proportions to those of ,daphnodon1 but the astragalus was less grooved for the tibia1 the claws were rather more retractile and the gait was probably more plantigrade4 ,there were so many cat-like features in the skeleton of ,daphnus1 that the observer cannot but suspect that these resemblances indicate a community of origin1 but1 until the ,eocene ancestors of the cats are found1 the question of relationship must remain an open one4 ,the most ancient member of the bear-dog phylum yet discovered appears to be one of the creodont family of the ,miacid1 found in the ,uinta ,eocene4 ,a short-lived branch of the canine stock was that of the so-called 8hyena-dogs10 a peculiar ,american type1 which abounded in the upper ,miocene and lower ,pliocene and then became extinct4 ,traced backward1 this brief series of species would appear to have sprung from the true wolves 7,tephrocyon7 of the middle ,miocene4 ,the upper ,miocene and lower ,pliocene genus lurodon had several species1 which differed considerably in size2 the commoner of these were large wolves with very modern type of body1 tail1 limbs and feet1 but having short and massive heads4 ,the premolars were extremely thick and heavy1 with such a resemblance to those of the hyenas1 that these animals have sometimes been mistakenly regarded as ancestral to that family4 ,the especial characteristic1 however1 of the series was in the form of the upper sectorial tooth1 which was much more feline than canine in construction and has given occasion for the generic name which means 8cat-tooth40 ,a fourth phylum of the ,canid1 which would seem to be represented in the modern world by the ,indian ,dhole1 or ,wild ,dog 7,cyon71 and perhaps by the ,brazilian ,bush-,dog 7,icticyon71 was characterized by the lower sectorial molar1 the heel of which was not basin-like1 as in the typical dogs1 but trenchant and consisted of a single sharp-edged cusp1 the external one of the primitive basin4 ,although there is no inherent improbability in the view that the ,dhole and the ,bush-,dog are derivatives of this phylum1 no positive statement can yet be made1 for the gap in the history is too great to be bridged with any assurance4 ,the fossil members of the series did not come down later than the middle or upper ,miocene and it is quite possible that the trenchant heel of the carnassial was developed more than once4 ,the middle and lower ,miocene members of the series are still very imperfectly known and it is only from the upper ,oligocene 7,john ,day7 that well-preserved skeletons have been obtained4 ,these pertain to an aberrant member of the phylum1 the genus ,temnocyon1 in which not only does the sectorial have a trenchant heel1 but the second lower molar also was trenchant1 having lost the two inner cusps1 while the upper molars were as large as in the bear-dogs4 ,temnocyon was a comparatively large animal and its skeleton had a mixture of primitive and advanced characters1 the latter predominating1 so that this genus was not only the largest but also the most specialized canid of its time4 ,there was the long1 heavy tail1 which all of the known ,oligocene carnivores possessed1 but the limbs were long and the gait was1 it would seem1 thoroughly digitigrade4 ,while the epicondylar foramen was retained by the humerus and the third trochanter by the femur1 those bones were otherwise very modern in form4 ,the feet were five-toed1 but the functional metapodials were parallel1 appressed and with something of the quadrate shape4 ,in very notable degree1 therefore1 the feet of ,temnocyon anticipated the characters which the true wolves acquired considerably later4 ,the less specialized ,mesocyon1 which was smaller1 was the ancestor of the ,miocene forms and was1 in turn1 very probably derived from the ,white ,river ,daphnus4 ,still a fifth phylum1 that of the short-faced dogs 7,enhydrocyon71 is very imperfectly known and has1 so far1 been found only in the lower ,miocene and upper ,oligocene4 ,these also may have been descended from ,daphnus1 but the connection is not clear1 nor has the relationship of the ,american genus to the extremely short-faced dogs of the ,european ,pliocene been determined4 ,illustration3 ,,fig4 #bfj4--,small1 fox-like dog 7,cynodictis gregarius7 of the ,white ,river4 ,restored from a skeleton in the ,american ,museum of ,natural ,history4 ,finally1 so far as ,north ,america is concerned1 there was a phylum of very small fox-like canids1 which ranged from the lower ,miocene to the upper ,eocene and were very abundant1 relatively speaking1 in the ,white ,river and ,john ,day4 ,the dental formula was the same as in ,canis and the skull was narrow and slender1 though the brain-chamber was proportionately capacious1 and the face was quite short4 ,the tympanic bull were large and inflated4 ,the body and tail were long and the limbs quite short and weak4 ,the humerus had no epicondylar foramen and the femur no third trochanter4 ,the five-toed feet had the spreading arrangement of the metapodials seen in the more primitive fissipedes generally and the claws were sharp4 ,in proportions and appearance these animals must have been more like civets or weasels than like dogs and it is evident that they were not swift runners4 ,the series had its earliest representatives 7,procynodictis7 in the ,uinta and was doubtless derived from the creodont family ,miacid4 ,the ,white ,river species are referred to the ,european genus ,cynodictis1 those of the ,john ,day and lower ,miocene to ,nothocyon1 and it has been suggested that this series gave rise to the foxes1 a suggestion which may prove to be true1 but the very long gap in time between these animals and the most ancient known foxes prevents any conclusion4 ,to determine the mutual relationships of the six phyla of ,canid which1 from the ,eocene onward1 inhabited ,north ,america in such numbers1 is a task of great difficulty and only a tentative solution of the problem can be offered4 ,the central stock would seem to be nearly represented by the ,white ,river ,daphnus1 leading through ,cynodesmus and ,tephrocyon1 of the ,miocene1 to the wolves4 ,a short-lived series1 apparently given off from ,tephrocyon1 was that of the hyena-dogs1 which flourished greatly in the upper ,miocene and lower ,pliocene and then became extinct4 ,another branch1 that of the bear-dogs1 was derived from ,daphnus1 through ,daphnodon to ,amphicyon1 ,dinocyon and ,borophagus1 the gigantic ,miocene and ,pliocene forms1 ending perhaps in ,hynognathus of the ,california ,pleistocene4 ,a third branch1 represented by ,mesocyon and ,temnocyon1 is believed to be continued to-day by the ,asiatic ,dhole and the ,brazilian ,bush-,dog4 ,the short-faced dogs 7,enhydrocyon7 are still very obscure4 ,the last phylum1 that of ,nothocyon1 ,cynodictis1 ,procynodictis1 had become distinct in the upper ,eocene and possibly gave rise to the foxes1 but this is highly conjectural4 #b4 ,felid4 ,cats ,the only other fissipede group whose development in ,north ,america may be followed for a long period is that of the ,sabre-,tooth ,tigers1 the subfamily ,machairodontin1 which have been extinct since the ,pleistocene2 the history of the ,true ,cats 7,felin7 is much more obscure4 ,in most respects the two subfamilies agreed closely and1 as they became separate at least in the early ,oligocene1 they furnish instructive parallel series4 ,the sabre-tooth cats were terrible beasts of prey1 which in most of the ,tertiary period ranged over the whole northern hemisphere and in the ,pleistocene or late ,pliocene extended throughout ,south ,america4 ,illustration3 ,,fig4 #bfa4--,skull of the ,pleistocene sabre-tooth tiger 7,smilodon californicus1 after ,matthew74 ,p4 #d1 fourth upper premolar1 sectorial4 ,the ,pleistocene genus ,smilodon 7,frontispiece7 belonged to nearly the whole western hemisphere and its various species were distributed from ,california and ,pennsylvania on the north1 to the ,argentine ,pampas on the south4 ,the most obvious and striking peculiarities of ,smilodon were in the teeth1 which were much reduced in number1 the formula being3 i #c_/c-b1 c #a_/a1 p #b_/b-a1 m #a_/a4 ,the upper canine was a great1 curved1 scimitar-like blade1 eight inches or more in length1 with broad inner and outer faces1 but quite thin transversely1 and with finely serrate posterior edge4 ,it is difficult to understand how these great tusks1 which would seem to have blocked the entrance to the mouth1 could have been effectively used1 unless the creature could open its mouth much more widely than any existing mammal1 so as to clear the points of the tusks1 and would then strike with them as a snake does with its fangs4 ,there are great anatomical difficulties in the way of accepting this explanation and the problem1 which is the same as that presented by the uintatheres 7p4 #ddf71 is still unsolved4 ,it is1 however1 quite certain that no arrangement which was disadvantageous1 or even inefficient1 could have persisted for such vast periods of time4 ,the lower canine was much diminished and hardly larger than an incisor4 ,the two upper premolars were the third and fourth of the original series2 the third was small1 but the fourth1 the sectorial1 was a very large and efficient shearing blade4 ,in addition to the two external trenchant cusps of the blade1 which are present in the ,carnivora generally1 the cats have a third small1 anterior cusp which in ,smilodon was large2 the internal cusp had almost disappeared4 ,the single upper molar was very small and so overlapped by the great carnassial as to be invisible from the side4 ,the third lower premolar was small and unimportant and most specimens had lost it1 leaving only the fourth1 which was larger and evidently of functional value4 ,the single molar was the sectorial1 a large1 thin1 flattened blade1 consisting of only two cusps1 one behind the other1 the trenchant edges of which met at nearly a right angle1 and there was no trace of a heel4 ,illustration3 ,,fig4 #bfb4--,upper teeth of ,smilodon1 left side4 ,p4 #d1 fourth premolar4 m4 #a1 first molar4 7,after ,matthew47 ,the skull was in appearance closely similar to that of one of the great modern cats1 such as the ,lion or ,tiger2 with extremely shortened face1 heavy and widely expanded zygomatic arches and very prominent sagittal crest4 ,the tympanic bull were large and inflated1 each divided by a septum into two chambers1 but were not visible from the side1 being covered externally by very large processes1 which served for the attachment of some of the great muscles of the neck4 ,the short1 rounded1 bullet-head of the true cats was thus repeated1 but there were in the skull several interesting differences of detail1 which it is not worth while to enumerate here4 ,suffice it to say1 that some of these differences were due to the retention of primitive characters in the skull of ,smilodon1 which have been lost in the modern felines1 and others to special developments1 in which the true cats did not share4 ,the lower jaw had on each side a small1 descending flange for the protection of the tusks1 which1 however1 projected well below these flanges when the jaws were shut4 ,the neck was heavy and the structure of its vertebr was such as to suggest the presence of unusually powerful muscles2 the back and loins were also uncommonly stout1 in the larger species heavier than in the ,lion or ,tiger1 but1 in marked distinction from those modern forms1 the tail was short4 ,the limbs were shorter and much heavier in relation to the size of the body than in the great existing cats and must have been extremely powerful4 ,the humerus usually had no epicondylar foramen1 which all the true felines possess1 though it was sometimes present4 ,the feet also were very stout and armed with large retractile claws2 the base of each claw was covered by a thin bony hood1 an outgrowth of the ungual phalanx1 which is very characteristic of the entire family4 ,the hind foot had five digits1 whereas no existing cat has more or less than four4 ,the appearance of these animals must have been very much like that of the ,lion or ,tiger1 aside from the unknown factors of mane and colour-markings1 but differed in the great tusks1 the short tail and the shorter and more massive legs and feet4 ,illustration3 ,,fig4 #bfc4--,skull of a sabre-tooth tiger 7,machairodus palmidens7 from the ,miocene of ,france4 7,after ,filhol47 ,p4 #d1 fourth upper premolar1 sectorial tooth4 ,on account of the very incomplete preservation of the material so far collected1 little is known of the sabre-tooth series in ,north ,america during the ,pliocene and ,miocene epochs4 ,remains of very large cats have been found in the lower ,pliocene and upper ,miocene1 but it is uncertain whether they belong to the feline or the machairodont subfamily4 ,some of the species have been referred to the genus ,machairodus1 which ranged from the lower ,pleistocene to the middle ,miocene of ,europe1 and the reference may be correct1 but is uncertain4 ,however1 the ,european representatives of that genus1 which are much better known1 will serve to show the developmental stage from which ,smilodon was undoubtedly derived4 ,the dental formula was the same as in the ,american genus1 though there were generally two premolars in the lower jaw and in ,smilodon generally but one2 the individual teeth were formed on the same plan as in the latter1 but were relatively smaller1 and the very small1 rudimentary upper molar was visible externally and was not overlapped and concealed by the great carnassial2 the sabre-like tusk had not attained such great proportions4 ,the skull of ,machairodus1 the only part of the skeleton which is definitely known1 was like that of ,smilodon on a much smaller scale1 but more primitive in several respects4 ,it was longer and had a less capacious brain-case and less prominent sagittal and occipital crests4 ,the large tympanic bull were conspicuous in the side-view of the skull1 as the processes for the attachment of the neck-muscles had no such development as in ,smilodon4 ,the descending flanges of the lower jaw were larger than in the latter4 ,the upper ,oligocene 7,john ,day7 contained a large variety of cat-like forms1 of which no less than five genera have been described2 one of them 7,pogonodon71 nearly as large as a ,lion1 would seem to have died out here without descendants1 and two others1 to which we shall return later1 so combined the characters of true felines and machairodonts as to be of uncertain reference4 ,two other genera1 which are much commoner and better known1 from the ,white ,river1 will be described from specimens of that stage4 ,the ,white ,river1 or lower ,oligocene1 had three highly interesting genera of machairodonts1 two of them known from nearly or quite complete skeletons4 ,one of these 7,hoplophoneus71 which was1 it can hardly be doubted1 the direct ancestor of the later typical machairodonts1 had several species1 which are found in the various levels of the ,white ,river beds4 ,the largest of these species was considerably smaller than ,machairodus1 and the smallest and most ancient was inferior to the modern ,wild ,cat4 ,the number of teeth was variable1 but normally greater than in the genera above described1 being i #c_/c1 c #a_/a1 p #c-b_/c-b1 m #a_/a1 #b #bh-cb4 ,the foremost premolar in each jaw was very small and often absent4 ,the upper canine was a long and curved1 but very thin1 scimitar1 finely serrate on both edges1 while the lower canine was but little larger than the incisors4 ,the carnassial teeth had a significant likeness to those of other fissipede families2 the upper one1 the fourth premolar1 was relatively smaller than in ,machairodus and its blade less effectively trenchant2 the accessory antero-external cusp was present1 though extremely small1 and the internal cusp1 which in ,smilodon had almost disappeared1 was quite large4 ,the lower sectorial1 the first molar1 though already cat-like and consisting of two thin1 broad and trenchant cusps in line1 yet had vestiges of the heel and sometimes of the inner cusp4 ,these vestiges were a connecting link between the highly specialized sectorial of the cats and the type usual among the ,fissipedia1 which is exemplified by the dogs4 ,the small upper molar was less reduced than in the ,miocene and ,pliocene genera and plainly consisted of a larger external and smaller internal cusp4 ,illustration3 ,,fig4 #bfd4--,white ,river sabre-tooth tiger 7,hoplophoneus primvus74 ,restored from a skeleton in the ,american ,museum4 ,oreodonts 7,merycoidodon7 in the background4 ,compared with that of other ,fissipedia1 the skull was short and broad1 but in comparison with that of the modern cats and of ,smilodon1 it was decidedly longer and narrower and the face was less abbreviated2 the resemblance to ,smilodon was very marked in the form of the cranium1 but1 of course1 the skull of ,hoplophoneus was distinctly more primitive in many respects4 ,thus1 the orbit was much more widely open behind1 the tympanic bull were but imperfectly ossified1 and the perforations1 or foramina1 in the base of the skull1 by which the nerves and blood-vessels communicated with the brain-chamber1 were quite different and had more resemblance to those of the ancient dogs 7e4g4 ,daphnus74 ,in the classification of the ,fissipedia much stress is laid upon the number and arrangement of these cranial foramina1 and it is very significant to find the primitive dogs and cats agreeing so much more closely than do the modern members of these families4 ,the lower jaw was relatively much stouter than in ,smilodon and the anterior flanges much more prominent1 projecting downward so far that1 when the jaws were closed1 the points of the tusks did not extend below the flanges4 ,the animal could have made no use at all of the sabre-tusks unless the mouth could have been opened so widely as to clear their points4 ,with close general resemblance1 allowing for the very inferior size1 the skeleton of ,hoplophoneus had many significant differences from that of ,smilodon4 ,the neck was shorter and the body1 especially the loins1 longer1 lighter and more slender and the tail very much longer1 equalling that of the ,leopard in relative length and surpassing it in thickness4 ,the limbs were much less massive and somewhat differently proportioned1 the upper arm being shorter and the fore-arm longer4 ,the humerus1 though far more slender than that of ,smilodon1 was remarkable for the great development of the deltoid and supinator ridges1 the latter1 together with the shape of the radius1 indicating very free rotation of the fore paw4 ,the very prominent internal epicondyle was pierced by a foramen1 and the femur had a distinct remnant of the third trochanter4 ,the five-toed feet were comparatively small1 but the claws were as completely retractile and as fully hooded as in any of the subsequent genera4 ,that ,hoplophoneus was a fierce destroyer1 is made evident by every part of its skeleton1 and1 like other cats1 it no doubt subsisted upon warm-blooded animals1 which it killed for itself1 the size of the prey being determined by the size and power of the particular species of the sabre-toothed genus4 ,in view of the probable extent of the ,oligocene forests1 the restoration 7,fig4 #bfd7 gives the animal a spotted coat and the general aspect is that of one of the modern spotted cats1 but the protruding ends of the tusks and the relatively long head distinguish it from any existing cat4 8,the presence of long1 knife-like canines is correlated with powerful grasping feet possessing highly developed retractile claws4 ,with its powerful feet the animal clung to its prey1 while it struck repeatedly with its thin1 sharp sabres0 7,j4 ,c4 ,merriam74 ,in the latter part of the ,white ,river stage lived one of the most highly specialized of the machairodonts1 so far1 at least1 as the dentition is concerned1 for only the skull is known4 ,this genus1 ,eusmilus1 which also occurred in the ,oligocene of ,europe1 was apparently an example of premature specialization which led to nothing1 for none of the subsequent genera could have been derived from it4 ,the teeth were reduced to a minimum in number3 i #c_/b1 c #a_/a1 p #b_/a1 m #a_/a1 #b #bd1 one lower incisor and at least one premolar less in each jaw than had ,hoplophoneus4 ,the canine tusk was very large and the flange of the lower jaw for its protection correspondingly elongated1 being more prominent than in any other machairodont4 ,the ,american species1 ,e4 dakotensis1 was the largest carnivore of its time and not greatly inferior in size to the ,lion4 ,still another ,white ,river machairodont1 ,dinictis1 differed in many interesting ways from its contemporary ,hoplophoneus1 being more primitive and departing less from the ordinary fissipede type of structure4 ,this is shown by the greater number of teeth1 which was normally1 i #c_/c1 c #a_/a1 p #c_/c1 m #a_/b1 #b #cd4 ,the upper carnassial had a considerably larger internal cusp and the trenchant blade did not have the accessory anterior cusp1 which is present in almost all other cats and was thus more dog-like than cat-like4 ,the lower carnassial was more feline1 but retained a remnant of the heel and of the inner cusp1 but the latter was variable1 being sometimes present in one side of the jaw and not in the other1 a sign that it was on the point of disappearance4 ,the upper molar was plainly a reduced form of the tritubercular tooth1 in plan like that of the dogs1 while the second lower molar was a very small1 single-rooted tooth4 ,no other ,american cat has such a primitive dentition as this1 and1 aside from the sabre-tusk1 which was not nearly so long as in ,hoplophoneus1 and the lower carnassial1 it might almost as well have belonged to a dog or musteline4 ,illustration3 ,,fig4 #bfe4--,primitive sabre-tooth 7,dinictis felina7 from the ,white ,river4 ,restored from specimens in the ,american ,museum and ,princeton ,university4 ,the skull was very like that of ,hoplophoneus1 but was still longer and somewhat different in shape1 owing to the higher forehead and lower occiput4 ,the primitive features of the cranial base1 such as the foramina1 the imperfectly ossified tympanic bull1 etc41 were repeated in ,dinictis1 but the lower jaw had much less prominent flanges for the protection of the tusks4 ,the limbs differed considerably from those of ,hoplophoneus in being relatively longer and more slender and retaining more primitive features1 such as the larger third trochanter of the femur4 ,the five-toed feet were decidedly small and weak1 and the claws1 though retractile1 were less so than in the other genus and were not hooded4 ,the gait was probably plantigrade or semi-plantigrade4 ,illustration3 ,,fig4 #bff4--,skull of ,dinictis squalidens1 ,white ,river4 7,after ,matthew47 p4 #d fourth upper premolar1 sectorial4 ,the relationships of ,dinictis and ,hoplophoneus are rather puzzling2 none of the known species of the former could have been ancestral to the latter1 for the two genera were contemporaneous4 ,dinictis was apparently the somewhat modified survivor of the ancestral stage and represented very nearly the common starting point of both the feline and machairodont subfamilies4 ,dr4 ,matthew has propounded the bold theory that this genus was the actual ancestor of the felines1 continuing the series through ,archlurus and ,nimravus of the ,john ,day to the unmistakable felines of the middle ,miocene4 ,this view runs contrary to the supposed 8law of the irreversibility of evolution10 a rule which many authorities look upon as well established4 ,the theory postulates a different mode of development from anything that we have so far encountered in the series previously described and supposes that the upper canine first lost its original form1 becoming a thin1 elongate and scimitar-like tusk1 while the lower canine was reduced almost to the proportions of an incisor and the lower jaw acquired a straight1 flat chin and inferior flanges for the protection of the tusks4 ,then1 after specialization had advanced so far1 it was reversed and the original condition regained4 ,this interesting hypothesis may possibly turn out to be true1 though personally ,i cannot accept it1 and1 should it do so1 it would necessitate a thoroughgoing revision of current opinions as to the processes of mammalian development4 ,illustration3 ,,fig4 #bfg4--,left pes of ,dinictis felina4 ,cal41 calcaneum4 ,as41 astragalus4 ,cb41 cuboid4 ,princeton ,university ,museum4 ,the only ,john ,day cat which was assuredly derived from ,dinictis was the large ,pogonodon1 previously mentioned4 ,illustration3 ,,fig4 #bfh4--,skull of false sabre-tooth 7,nimravus gomphodus7 from the ,john ,day4 7,after ,matthew47 p4 #d fourth upper premolar1 sectorial4 ,also in the ,john ,day stage lived ,archlurus and ,nimravus1 which1 as was noted above 7p4 #bdi71 have been called the 8false sabre-tooths10 for in them the upper canine was not much larger than the lower and the latter1 though smaller than in the felines1 was yet very much less reduced than in the true machairodonts4 ,the skull closely resembled that of ,dinictis1 but the lower jaw was without flanges4 ,the limbs were long and slender and the feet long and digitigrade4 ,the pes had only four digits1 of which the median pair was elongated and the lateral pair shortened1 so as to produce considerable resemblance to the pes of the dogs1 and the claws were partially retractile4 ,the proportions of the body1 limbs and feet were suggestively like those of the ,cheeta1 or ,hunting ,leopard 7,cynlurus jubatus7 of ,india1 the generic name of which means 8dog-cat10 and it is quite possible that the ,cheeta may have been derived from some member of this 8false sabre-tooth0 series1 though the connecting links are unknown4 ,these cursorial cats quite displaced the leaping machairodonts of the ,hoplophoneus type1 at least in the ,oregon region at a time when1 it will be remembered1 that region had a remarkable variety of dogs4 ,in other parts of the continent1 of which we have no record1 the true machairodonts must have been thriving1 as may be inferred from their comparative abundance in the later formations4 ,concerning the habits of these cursorial cats1 ,professor ,merriam says3 8,when the canines are not developed to the dagger-like form for stabbing1 the premolar teeth serve a more definite purpose in the destruction of prey and would be less subject to reduction4 ,the view suggested above finds support in that such evidence as we have indicates that during the deposition of the ,middle ,john ,day beds this region was in the main a country of open plains1 offering advantages to running types of carnivores1 and that during this epoch the ,archlurus-,nimravus type of feline was by far the most common form i4e4 of cats40 ,the derivation of these cats is still obscure1 but their likeness to certain forms of the ,european ,oligocene suggests that they were immigrants4 ,the true cats of the subfamily ,felin include the great variety of living forms1 large and small1 from the ,lion and ,tiger at one extreme to the ,domestic ,cat at the other4 ,there is great difference among naturalists with regard to the nomenclature of the ,recent cats2 some make a considerable number of separate genera1 while others include all the species1 except the lynxes and the ,cheeta1 in the genus ,felis4 ,for the purposes of this book the latter practice is the more convenient and will be followed4 ,in ,felis the dental formula is3 i #c_/c1 c #a_/a1 p #b-c_/b1 m #a_/a1 #b #bh-cj2 the canines are large and strong1 of oval section1 and the upper one is but little larger than the lower2 there are two large and functional premolars in each jaw1 and an additional very small one may or may not be present in the upper jaw4 ,the upper sectorial has a large shearing blade1 with well-developed anterior accessory cusp1 and the inner cusp1 which in ,smilodon had almost disappeared1 is quite large and carried on a separate root4 ,the lower sectorial is composed of two cusps only1 all traces of the heel and of the inner cusp having disappeared4 ,the single upper molar is very small and usually concealed by the sectorial4 ,the skull is very short and broad1 and the shortening of the jaws gives great power to the biting muscles1 because of the more favourable leverage4 ,the zygomatic arches are very stout and curve out boldly1 contributing much to the rounded shape of the head2 the orbits are almost encircled in bone4 ,the large tympanic bull are two-chambered and there is no alisphenoid canal1 but in several other respects the base of the cranium differs markedly from that of ,smilodon4 ,the lower jaw is without flanges and there is no angle between front and sides4 ,illustration3 ,,fig4 #bfi4--;,dentition of ,lynx 7,l4 rufus71 left side4 i4 #c1 external upper incisor4 i4 #a1 first lower incisor4 c4 canine4 p4 #c1 p4 #d1 third and fourth premolars4 m4 #a1 first molar4 ,illustration3 ,,fig4 #bgj4--,upper teeth of ,puma 7,felis concolor71 left side4 p4 #d1 fourth premolar4 m4 #a1 first molar4 ,the neck is short1 the body long and the tail is long in most of the species1 but short in the lynxes4 ,the limbs are relatively longer and less massive than in ,smilodon1 and there are five toes in the manus1 four in the pes2 the claws are hooded and retractile4 ,the western hemisphere at the present day contains none of the very large species1 the ,puma and ,jaguar being the largest2 but this was not true of the ,pleistocene1 where a huge cat 7,felis atrox71 surpassing the ,lion in size1 ranged over the southern half of ,north ,america4 ,enormous cats also lived in the lower ,pliocene and upper ,miocene of the ,great ,plains region1 but are not sufficiently well known for reference to either subfamily4 ,illustration3 ,,fig4 #bga4--,skull of ,puma 7,felis concolor74 p4 #d1 upper carnassial4 ,the upper molar is concealed4 ,the history of the true felines has been but partially deciphered1 and can1 as yet1 be traced back only to the middle ,miocene1 the genus ,pseudlurus representing the series both in ,europe and ,north ,america4 ,in this genus the dental formula was nearly the same as in ,felis1 but there was frequently an additional small premolar in the lower jaw and the sectorials were more primitive1 the upper one having the accessory anterior cusp in a merely incipient stage and in the lower one there was a vestige of the heel4 ,the upper canine was considerably longer than the lower1 thinner and more blade-like than in ,felis1 which1 so far as it goes1 is in favour of ,dr4 ,matthew's theory 7p4 #eda74 ,what little is known of the skull and skeleton of ,pseudlurus agrees with the modern cats4 ,illustration3 ,,fig4 #bgb4--,left manus of ,domestic ,cat 7,felis domestica1 after ,jayne74 ,the horny claws are left in place1 covering the ungual phalanges4 ,while it is not feasible to trace the series of true felines to an earlier stage than the middle ,miocene1 there can be no doubt that the subfamily was derived from the same stock as the machairodonts and it is probable that the ,white ,river ,dinictis nearly represents the common starting point for both series2 the resemblances between ,dinictis and such primitive dogs as ,daphnus are suggestive of a common origin4 #c4 ,procyonid4 ,raccoons1 etc4 ,an almost exclusively ,american family of ,fissipedia is that of the raccoons1 which includes not only the latter 7,procyon71 but also the coatis 7,nasua71 curious animals1 with long1 flexible1 pig-like snouts1 the cacomistles 7,bassariscus7 and kinkajous 7,potos74 ,in addition to these ,american forms1 there is an outlying ,asiatic genus1 the ,panda 7lurus7 of the southeastern ,himalayas1 the last of a series which goes back to the ,european ,pliocene4 ,the ,procyonid are animals of small and moderate size1 largely arboreal in habits and subsisting upon a mixed diet of fruit1 eggs1 insects and the like2 the teeth are adapted to this diet and the sectorials have mostly lost their shearing form and the molars are tuberculated for crushing and grinding4 ,the species generally have long tails1 except in the raccoons proper1 in which the tail is of medium length1 and five-toed1 plantigrade feet1 with naked soles4 ,fossil members of this family are very rare in ,tertiary formations and its history is therefore but scantily known2 in the lower ,pliocene have been found fragmentary remains with less specialized teeth1 which appear to belong to the direct ancestor of ,bassariscus4 ,the upper ,miocene genus ,leptarctus was an undoubted member of the family1 and1 while it would seem not to have been in the direct line of any of the modern forms1 it was near to the common ancestry of the ,american genera1 so far as the imperfect specimens enable us to judge4 ,illustration3 ,,fig4 #bgc4--;,dentition of ,raccoon 7,procyon lotor71 left side4 i4 #c1 external incisor4 c41 canine4 p4 #d1 fourth premolar4 m4 #a1 first molar4 ,by far the most primitive representative of the family yet discovered is the lower ,miocene genus ,phlaocyon1 which connected the ,procyonid with the ,oligocene genus of dogs1 ,cynodictis 7p4 #ebi74 ,the dentition resembled that of the latter1 with several differences1 which were all changes toward the ,procyonid4 ,all the cusps were lower and blunter than in ,cynodictis2 the premolars were small1 thick and closely crowded together and the upper sectorial1 while still trenchant1 had a postero-internal cusp1 which is found in none of the ,canid and was a first step toward the tuberculated pattern of the raccoons1 and the lower sectorial had a very low cutting blade and large heel2 the other molars of both jaws were low1 wide and of subquadrate shape4 ,the skull was short and broad1 with the face as much shortened and the orbits as far forward as in ,procyon1 but the brain-case was narrower1 less capacious1 and the lower jaw had the curved form and much the same character as in the modern genus4 ,the limbs were relatively more slender than in the latter and the five-toed feet were more canine than procyonine in the proportions of the digits4 ,the discovery of ,phlaocyon by ,dr4 ,matthew was an event of capital importance1 as showing the highly probable derivation of the raccoons from ,cynodictis and thus bringing another fissipede family into relationship with the dogs4 #d4 ,ursid4 ,bears ,the present distribution of the bear family is all but exclusively northern1 as there is but one ,african species1 confined to the northwestern corner of that continent1 and one in the ,andes of ,peru and ,ecuador1 all the others belonging to ,eurasia and ,north ,america4 ,illustration3 ,,fig4 #bgd4--;,dentition of ,black ,bear 7,ursus americanus74 i4 #c1 external incisor4 c41 canine4 p4 #a1 first premolar4 p4 #d1 fourth premolar4 m4 #a1 first molar4--,below is a view1 on a larger scale1 of the grinding surface of the fourth premolar and first molar1 upper jaw4 ,structurally1 the family is very distinct and the dentition is quite peculiar4 ,the incisors and canines resemble those of other ,fissipedia2 the three anterior premolars are very small1 single-rooted and often shed early2 the carnassials have lost their trenchant character2 and the molars1 which are usually longer than wide1 are tuberculated1 somewhat resembling those of pigs4 ,almost all the bears live principally upon vegetable food1 and even the ,polar ,bear1 which feeds upon fish and seals1 will eat grass and berries in the brief ,arctic summer2 thus1 the shearing teeth of the strictly carnivorous types are unnecessary to these animals4 ,the skull is not unlike that of the dogs in shape1 but the tympanic bull are much flattened and the entrances to them are long1 bony tubes1 while the cranial foramina are nearly as in the dogs4 ,the body is very heavy and the tail always short4 ,the limbs are short and thick2 the humerus has lost the epicondylar foramen in all existing species except the ,south ,american ,spectacled ,bear 7,tremarctos ornatus74 ,the plantigrade feet have naked soles 7except in the ,polar ,bear7 and each foot has five well-developed and functional digits1 armed with very long1 sharp and non-retractile claws4 ,illustration3 ,,fig4 #bge4--,restored head of the ,short-faced ,bear 7,arctotherium bonerense74 ,from a skull in the ,national ,museum1 ,buenos ,aires4 ,the ,pleistocene representatives of the family in ,america included species of the true bears 7,ursus7 and of the very large short-faced bears 7,arctotherium7 which ranged over both ,north and ,south ,america4 ,in ,arctotherium the dentition was less modified2 the larger premolars were very closely crowded together and the molars were nearly square2 the lower jaw was almost as much curved as in the raccoons4 ,the humerus retained the epicondylar foramen4 ,the family1 which was of ,old ,world origin1 may have reached ,america in the lower ,pliocene1 but was rare until the late ,pleistocene4 ,arctotherium has not been found in the eastern hemisphere1 but that1 of course1 is no proof that the genus was not an immigrant from ,asia4 ,on the other hand1 it may have been a peculiar ,american development from ,pliocene immigrants4 ,in the ,old ,world1 bears were first distinguishable in the upper ,miocene1 and may be there traced back to forms which were unmistakably derivatives of the early dogs4 #e4 ,mustelid4 ,mustelines ,the last fissipede family1 which has1 or has had1 representatives in the western hemisphere is that which includes a great variety of small carnivores1 such as minks1 martens1 skunks1 badgers1 otters1 etc41 and was likewise of ,old ,world origin1 though now of universal distribution1 except in ,australia and ,madagascar4 ,these are fierce and bloodthirsty beasts of prey1 most of them strictly carnivorous and often killing in mere wantonness more than they can devour4 ,though now quite numerous and varied in ,north and ,south ,america1 they are decidedly less so than in the eastern hemisphere and comparatively few peculiar types have originated here4 ,owing to the small size and fragility of the skeletons1 they have not been well preserved as fossils1 and little can be done as yet in tracing out the genealogy of the various phyla4 ,the mustelines have shortened jaws and a reduced number of teeth1 the molars being #a_/b or even #a_/a and the premolars varying from four to two1 though three in each jaw is the usual number4 ,the cranium is generally very long and the facial part of the skull short1 but the soft snout may add considerably to the length of the face4 ,the tympanic bull are single-chambered and little inflated1 and the lower lip of the entrance is extended2 the hard palate is usually continued well back of the teeth4 ,the body is very long and the tail variable and1 in most of the genera1 is short rather than long4 ,the limbs are short1 the feet1 except in one genus1 five-toed and plantigrade or semi-plantigrade1 and the claws are non-retractile4 ,terrestrial1 arboreal1 burrowing1 aquatic and marine forms are all represented in the family4 ,so far as ,north ,america is concerned1 it is scarcely practicable to do more than catalogue the genera of the successive geological epochs4 ,pleistocene mustelines were very modern in character1 differing little from those now inhabiting the continent1 though in some cases with different ranges1 according to climatic fluctuations4 ,badgers1 martens1 skunks and others occurred then very much as they do now and the ,boreal ,wolverene extended down to ,pennsylvania4 ,little is known of ,pliocene mustelines1 the ,blanco having yielded fragments of only one genus of uncertain affinities and though several genera occurred in the lower ,pliocene1 but one1 a marten 7,martes71 can be identified4 ,unquestionably1 ,north ,america had many more ,pliocene members of the family1 but the conditions of preservation were unfavourable4 ,much the same is true of the ,miocene stages4 ,in the upper ,miocene there were a marten 7,martes71 a weasel 7,mustela7 and two otters 7,potamotherium and the modern ,lutra71 of which the marten and the more primitive otter went back to the middle ,miocene4 ,in the lower ,miocene were several mustelines quite different from any now existing4 ,one of those1 ,megalictis1 was truly gigantic1 with a skull nearly as large as that of a ,black ,bear and having heavy1 pointed claws4 ,this and a similar genus1 lurocyon1 were related to the ,ratel 7,mellivora7 of ,india and ,africa and1 more closely1 to the ,wolverene4 ,oligobunis1 a much smaller animal1 was apparently of the same group4 ,this genus was also in the upper ,oligocene1 but there represented by a larger species1 which was as large as a badger4 ,the ,white ,river beds have yielded but a single genus1 ,bunlurus1 which was the most primitive of ,american mustelines and had four premolars and two molars in each jaw1 though the second upper molar was extremely small4 ,the face was much less shortened than in the modern weasels and the tympanic bull were short and strongly inflated and had no tubular entrance1 and were thus canine rather than musteline in form4 ,the bony palate was not extended back of the teeth as it is in the modern genera4 ,the same primitive group was much more abundant in the ,european ,oligocene1 migrating probably from ,asia into ,europe as well as into ,north ,america4 ,,south ,,american ,,fissipedia ,the history of the ,south ,american carnivores is a comparatively brief one2 the southern continent has representatives of the same five families as the northern1 but most of the genera are different1 the time since the great southward migration having been sufficient for the development of peculiar forms in the new environment4 ,among the dogs1 there are to be noted the curious1 close-haired1 long-bodied and short-legged ,bush-,dog 7,icticyon7 and the fox-like wolves 7,cerdocyon71 but there are no true foxes4 ,of the cats1 the ,puma differs little from that of ,north ,america1 and the ,jaguar 7,felis onca7 and ,ocelot 7,f4 pardalis7 also range into the northern continent1 but several small cats are confined to ,south ,america1 which has no lynxes4 ,there is but one bear 7,tremarctos ornatus7 of ,andean range4 ,of the ,procyonid1 the northern ,procyon lotor is replaced by the ,crab-eating ,raccoon1 ,p4 cancrivorus1 while the coatis 7,nasua7 and kinkajou 7,potos7 are chiefly ,neotropical4 ,except for the otters1 the genera of ,mustelid are nearly all different2 there are no badgers and a different genus of skunks 7,conepatus7 replaces the northern ,mephitis2 the ,grison 7,grison71 ,tayra 7,tayra7 and the ,patagonian ,lyncodon are peculiar4 ,even less can be done to trace the evolution of the ,south ,american genera than for the forms of the northern continent1 whence migrated the more or less different ancestors of the former4 ,the ,pleistocene has yielded most of the modern genera1 both existing and extinct species4 ,an example of the latter was ,procyon ursinus from the ,brazilian caverns1 a truly gigantic ,raccoon1 as large as a bear4 ,the sabre-tooth tigers 7,smilodon7 and short-faced bears 7,arctotherium7 were shared with ,north ,america4 ,in the ,pliocene a bear1 a raccoon and a dog were the only known fissipedes1 and in the ,miocene none have been found1 their place being taken by flesh-eating marsupials4 99 99 99 99 99 ,while the history of the ,fissipedia1 as outlined in the preceding pages1 is sadly incomplete as compared with that of many ungulates1 it is nevertheless highly suggestive4 ,in each family the advance of specialization and adaptation to a narrow range of habits may be followed2 generally speaking1 the teeth were diminished in number and increased in size and were either simplified by the loss of parts1 as in the cats1 or complicated by the addition of new elements1 as in the bears and raccoons4 ,the brain grew larger and more convoluted and the cranium more capacious2 in most of the families1 the face was shortened1 notably in the cats and mustelines1 while in others1 especially the dogs1 it was elongated4 ,in all of the early types there was a long and heavy tail1 but in most series it underwent more or less reduction4 ,there was little reduction of digits1 and no fissipede has less than four4 ,in modern dogs and cats there are five digits in the manus and four in the pes and the hyenas have four in each1 as has one genus of mustelines2 other modern genera throughout the suborder are pentadactyl4 ,it is significant that the more ancient members of the various families differed less than do the modern ones2 the various groups1 as they are traced back in time1 would seem to be converging to a common ancestry1 of which the lower ,oligocene dogs were the least changed representatives1 and it is probable that all the families of the ,fissipedia were derived1 directly or indirectly1 from a single ,eocene group of primitive flesh-eaters4 ,the families1 none of which is extinct1 are not all of equal antiquity4 ,so far as now appears1 the dogs and viverrines are the most ancient1 having become distinct in the upper ,eocene2 in the ,oligocene were added the mustelines and cats2 the raccoons branched off from the dogs in the lower ,miocene1 as did the bears in the upper ,miocene4 ,finally1 the hyenas appeared in the lower ,pliocene1 seemingly derived from the viverrines4 ,the dogs passed through the greater part of their development in ,north ,america1 where1 during the ,oligocene and ,miocene1 they were very abundant and varied1 while at the same time they were comparatively rare in ,europe and belonged chiefly to the phylum of the bear-dogs4 ,on the other hand1 the remaining four families are of ,old ,world origin1 the bears and mustelines migrating to ,america1 while the viverrines and hyenas did not4 ,,suborder ,,creodonta4 ,,primitive ,,flesh-,,eaters ,this group long preceded the ,fissipedia in time1 for they began their recorded history in the ,paleocene and became extinct in the ,oligocene4 ,through one family1 the ,miacid1 the creodonts were broadly connected with the fissipedes1 and it seems probable that that family was the ancestral stock from which all the fissipede families were derived4 ,the other creodont families died out without leaving descendants4 ,there is some difference of practice as to the number of families to be admitted2 the table contains those listed in ,professor ,osborn's book and also adopted by ,dr4 ,schlosser4 ,i should prefer a somewhat larger number of family groups1 but the matter is one of secondary importance4 ,many genera are omitted4 ,i4 ,,oxycl,,nid4 ,oxyclnus1 ,paleoc4 ,deltatherium1 do4 ,,ii4 ,,arctocyonid4 ,clnodon1 ,paleoc4 ,anacodon1 low4 ,eoc4 ,,iii4 ,,mesonychid4 ,triisodon1 ,paleoc4 ,dissacus1 do4 ,pachyna1 low4 ,eoc4 ,mesonyx1 mid4 ,eoc4 ,dromocyon1 do4 ,harpagolestes1 mid4 and up4 ,eoc4 ,,iv4 ,,oxy,,nid4 ,palonictis1 low4 ,eoc4 ,oxyna1 do4 ,patriofelis1 mid4 ,eoc4 ,limnocyon1 do4 ,machairoides1 do4 ,oxynodon1 up4 ,eoc4 ,v4 ,,hy,,nodontid4 ,sinopa1 mid4 ,eoc4 ,stypolophus1 low4 and mid4 ,eoc4 ,tritemnodon1 mid4 ,eoc4 ,pterodon1 low4 ,oligo4 ,hynodon1 do4 ,,vi4 ,,miacid4 ,didymictis1 ,paleoc4 and low4 ,eoc4 ,viverravus1 mid4 ,eoc4 ,miacis1 low4 ,eoc4 ,uintacyon1 low4 to up4 ,eoc4 ,odectes1 mid4 ,eoc4 ,vulpavus1 do4 ,palarctonyx1 do4 ,the ,creodonta were an extremely varied assemblage1 of carnivorous1 omnivorous and presumably insectivorous habits1 so that few statements1 not subject to exceptions1 can be made of them all4 ,only seven genera are known from skeletons1 and several more from skulls1 but most are represented only by jaws and teeth2 limb- and foot-bones1 however1 give us a conception of the general structure of a considerable number4 ,as a rule1 the dentition was complete1 according to the formula1 i #c_/c1 c #a_/a1 p #d_/d1 m #c_/c1 #b #dd1 but the first premolar or the last molar may be lost4 ,the canines were always large1 as was befitting for beasts of prey4 ,in only one family1 the ,miacid1 were the carnassial teeth confined to a single pair and those the same as in the ,fissipedia1 the fourth upper premolar and first lower molar2 in all the other families there were either no sectorial teeth1 or else there was more than one pair4 ,in the ,fissipedia the first is the largest of the lower molars1 while in the ,creodonta 7except the ,miacid7 it was usually the smallest4 ,the premolars were generally simple1 compressed-conical teeth and the molars1 with all their great variety1 may be reduced to a common plan2 those of the upper jaw were primitively tritubercular1 with a triangle of two external and one internal cusps1 and those of the lower jaw were in two distinct parts1 an anterior1 elevated triangle of three cusps and a low heel of two4 ,the skull was almost always very large in proportion to the size of the animal2 the cranium1 though long1 was of small capacity and the face varied much in length in the different families4 ,primitively1 the face and jaws were short in correlation with the small size of the teeth1 and this primitive condition was modified in two opposite directions2 in one the face and jaws were elongated1 as the teeth enlarged1 and in the other they were shortened still further4 ,the zygomatic arches were stout and curved out strongly from the sides of the skull1 making very wide openings1 and1 in almost all cases1 the sagittal and occipital crests were very high1 as would be necessary from the combination of powerful jaws and small brain-case 7see p4 #fc74 ,the tympanic bull were not ossified4 ,the brain was extremely small1 especially in the more ancient genera1 and the convolutions were almost always few and simple1 which indicates a low grade of intelligence and very marked inferiority to the ,fissipedia4 ,in all the genera of which sufficient material has been obtained the body was long and had #ai or #bj trunk-vertebr3 in the lumbar and posterior part of the dorsal regions the processes by which the successive vertebr were articulated together 7zygapophyses7 were cylindrical and interlocking1 as in the artiodactyl ungulates 7p4 #cfj74 ,to this general statement1 the ,miacid formed a partial exception4 ,the tail was very long and heavy in all the forms of which the caudal vertebr are known1 and this was probably true of all4 ,the limbs were short and generally heavy2 the femur had the third trochanter and the humerus1 save in a few of the later genera1 the epicondylar foramen1 and the manus could1 in nearly all1 be freely rotated4 ,except in the most advanced forms of one family1 the ,mesonychid1 the feet were five-toed and plantigrade1 or semi-plantigrade1 and of decidedly primitive structure4 ,the scapho-lunar bone of the ,fissipedia 7see p4 #eai7 was not formed1 its three elements1 with very few exceptions1 remaining separate4 ,the astragalus nearly always had a shallow groove1 or none at all4 ,the claws were thick and blunt and the ungual phalanges cleft at the end1 except in the ,arctocyonid and ,miacid1 which had sharp claws and uncleft phalanges4 ,from this brief description1 it is obvious that the ,miacid occupied a very isolated position among the creodonts and1 in my judgment1 it would be better to transfer that family to the ,fissipedia and include the others in a separate order4 ,throughout the ,paleocene and ,eocene epochs the ,creodonta were numerous and varied1 the first of the ,fissipedia appearing in the upper ,eocene4 ,till then the creodonts were the only predaceous mammals in ,north ,america and ,europe1 and they were especially abundant in the former4 ,most members of the suborder and all the ,paleocene forms were of small or moderate size1 but some of the ,eocene species were very large4 ,in the ,uinta the creodonts were greatly decreased in numbers and in the ,white ,river there were only two genera of one family1 the ,hynodontid1 and since the ,oligocene the suborder has been extinct4 #a4 ,miacid4 ,fissipede-like ,creodonts ,it is unfortunate that no member of this family is known from a complete skeleton1 but the material collected is sufficient to give a fairly adequate conception of these most interesting animals4 ,these were the only creodonts with a single pair of carnassials1 the fourth upper premolar and first lower molar1 but in some of the genera the carnassials did not differ greatly from the other teeth4 ,in the various genera the skull differed considerably in length and in the proportions of cranium and face2 the brain-case was larger than in most other creodonts and the brain more advanced1 though smaller than in the fissipedes1 and the sagittal and occipital crests were very prominent2 the tympanic bull were not ossified4 ,the humerus had the epicondylar foramen and the femur the third trochanter2 in the wrist the scaphoid1 lunar and central were separate1 almost the only important difference from the ,fissipedia and merely the primitive stage of the latter4 ,the feet were pentadactyl and the digits were arranged in spreading fashion2 the claws were small1 sharp and partially retractile and the ungual phalanges not cleft at the tip4 ,within the family several different phyla may be distinguished1 one of which 7,miacis--,uintacyon7 led to the dogs1 another to the bear-dogs1 or amphicyons4 ,a third phylum 7,didymictis--,viverravus7 is by several authorities regarded as ancestral to the civet family1 or viverrines1 of the ,old ,world1 and a fourth 7,odectes1 ,vulpavus7 as the forerunner of the kinkajous 7,potos74 ,except for the connection with the dogs1 the hiatus in time between the supposed ancestors and descendants is too great to permit any confident statements4 ,it seems very probable1 however1 that the ,miacid represented the common stock1 from which the fissipede families were all derived1 directly or indirectly1 though for most of them the details of the connection remain to be learned4 ,we find thus a group separating itself from the other creodonts in the older ,paleocene and gradually assuming fissipede characteristics1 at the same time dividing into several phyla4 ,in the upper ,eocene this group passed almost imperceptibly into the ,fissipedia1 more obviously into the dog family1 which1 as we have seen1 represents the central line of fissipede development4 #b4 ,mesonychid ,this family displayed1 in certain respects1 the highest degree of specialization attained by any creodonts1 for they were the only ones which acquired cursorial limbs and feet4 ,the mesonychids were prevailingly1 but not exclusively1 a ,north ,american family and their range in time was through the ,paleocene and ,eocene4 ,the teeth1 in the more advanced genera1 had a curious mingling of primitive and specialized characters and none were sectorial in the proper sense of the word4 ,the incisors were small1 the canines large and bear-like and the premolars simple4 ,the upper molars were very primitive1 retaining the original tritubercular pattern1 except that the two outer cusps were joined together1 but the lower molars had lost all the internal cusps1 which gave them a carnassial appearance2 they were not sectorial1 however1 for their cusps wore directly against the upper teeth1 not shearing past them1 and were greatly blunted and worn down by use4 ,the last of the family was ,harpagolestes1 of the ,uinta and ,bridger1 one of the largest of the creodonts4 ,the skull1 which was of disproportionate size1 exceeded that of the ,grizzly ,bear2 the upper profile of the skull had considerable resemblance to that of a bear in the steep forward descent at the fore head4 ,the teeth were more reduced than in the other members of the family through the loss of the second premolar and third molar of the upper jaw4 ,the skeleton is little known1 but the humerus had a long and prominent deltoid crest and an epicondylar foramen4 ,illustration3 ,,fig4 #bgf4--,upper teeth1 right side1 of ,mesonyx obtusidens1 showing the grinding surface4 ,in the middle ,bridger stage were closely allied and very similar genera1 ,mesonyx and ,dromocyon 7,fig4 #aci1 p4 #bfi71 which were like small1 big-headed wolves1 for the skull was as long as that of a ,black ,bear4 ,though the cranium was very long1 the brain-chamber was very small and the sagittal crest enormously high1 to afford surface for the attachment of the powerful jaw-muscles4 ,the tympanic bull were ossified and had quite long1 tubular entrances1 a feature which has been found in no other creodont skull4 ,the face and jaws were also elongate1 giving the head quite a wolf-like appearance4 ,the neck and body were of moderate length1 but the tail was extremely long1 slender and whip-like4 ,the limbs and feet were more specialized than in any other creodont and the changes were all in the direction of adaptation to swift running4 ,the humerus was very smooth1 with low ridges1 and1 alone among creodonts1 had in these genera no epicondylar foramen1 though the femur retained the third trochanter4 ,the radius was broad and so interlocked with the humerus as to prevent any rotation of the manus4 ,the feet were four-toed and much resembled those of the modern dogs and hyenas4 ,in each foot the metapodials were closely appressed and parallel1 not spreading1 but arranged in two symmetrical pairs1 a longer median and shorter lateral pair1 much on the artiodactyl plan2 the ankle-bone 7astragalus7 also had an artiodactyl look1 with its deeply grooved surface for the tibia and pulley-like lower end4 ,the ungual phalanges were so short and broad as almost to suggest hoofs rather than claws4 ,it is clear that the gait was as fully digitigrade as in a modern wolf and these were the only creodonts of which this is known to be true4 ,these were somewhat puzzling animals2 the whole structure of the limbs and feet was that of cursorial types1 but the broad1 blunt claws do not suggest the running down and capture of prey1 nor were the teeth those of savage killers4 ,the speed may have been defensive1 to escape from enemies1 and the food may have been largely vegetable4 ,ancestors of these ,bridger genera have not been found yet in the ,wasatch1 a time when the family was represented by ,pachyna1 some of the species of which were very large1 rivalling ,harpagolestes1 which was descended from one or more of them4 ,pachyna had extremely massive teeth and was not improbably a carrion-feeder of hyena-like habits1 and it retained the epicondylar foramen of the humerus and pentadactyl feet4 ,much more primitive was ,dissacus1 of the upper ,paleocene1 which was very probably the direct ancestor of both the ,wasatch and the ,bridger genera4 ,the upper molars were substantially as in the latter1 but the lower molars had the internal cusp of the primitive triangle1 though the heel was trenchant1 and had lost its inner cusps4 ,the feet had five well-developed digits1 which were arranged in spreading fashion1 and the gait was plantigrade4 ,the claws were longer1 more pointed and much less hoof-like than in the ,bridger genera4 ,the ,puerco genus ,triisodon may or may not have been directly ancestral to ,dissacus2 at all events1 it was very nearly what the desired ancestor must have been4 ,the teeth were much less specialized than in ,dissacus2 the tritubercular upper molars were broader and their external cusps were more separated1 while in the lower molars the anterior triangle was made up of three nearly equal cusps and the heel was low and basin-shaped4 ,the skull had an extremely narrow brain-case and a long1 heavy sagittal crest4 ,the most interesting feature in the history of the ,mesonychid is the demonstrable derivation of the cursorial1 digitigrade1 four-toed and almost hoofed ,bridger genera from the plantigrade1 five-toed ,torrejon genus1 which had sharp claws4 ,to all appearances1 this family was the creodont analogue of the hyenas4 #c1 #d4 ,arctocyonid and ,oxyclnid ,this second creodont family which had no carnassial teeth has received the not very happily chosen name of ,arctocyonid1 or 8bear-dogs10 though they were not related to either bears or dogs4 ,the family was a very ancient one and has been found only in the ,paleocene and lower ,eocene 7,torrejon and ,wasatch7 of ,north ,america and ,europe4 ,the molar teeth were very low-crowned and quadritubercular1 with numerous small tubercles in addition to the four principal cusps1 a pattern which was rather pig-like than bear-like4 ,the ,wasatch genus ,anacodon1 known only from jaws and teeth1 had reduced premolars1 both in size and number1 while in the ,torrejon genus1 ,clnodon1 the premolars1 though small1 were present in full number4 ,the skull was like that of ,mesonyx in the relative lengths of cranium and face1 the very small size of the brain-case and the great prominence of the occipital and sagittal crests4 ,the feet were pentadactyl and plantigrade and the claws were long1 thin and pointed1 and the ungual phalanges were not cleft at the tip1 the only creodont family1 except the ,miacid1 of which this was true4 ,of the ,oxyclnid1 very little is known and they may not have been creodonts at all4 ,they were quite small animals1 with sharp-cusped tritubercular upper molars and lower molars with high anterior triangle and low heel4 ,this is the type of dentition from which all the divergent creodont types were doubtless derived4 ,the family was ,paleocene4 #e4 ,hynodontid ,this was the last of the creodont families to survive1 being quite common in the lower ,oligocene of ,north ,america and ,europe and in the upper ,eocene of the latter also4 ,the family became extinct in the upper ,eocene of ,north ,america and the ,white ,river genera were not of native origin1 but migrants from the ,old ,world4 ,one of the more abundant predaceous genera of ,white ,river times was the ,european ,hynodon2 it was represented by several species which ranged in size from a fox to a ,black ,bear4 ,in this genus the dentition was somewhat reduced1 the incisors often numbering #b_/b and the molars constantly #b_/c2 there were three pairs of carnassial teeth on each side1 of which the pair formed by the second upper and third lower molar was the largest and most efficient1 the other pairs being the first upper and second lower molar1 the fourth upper premolar and first lower molar1 the latter the smallest of the three4 ,the upper molars had lost the internal cusp and the remaining1 external portion consisted of a flattened-conical anterior cusp and a posterior trenchant ridge2 the milk-teeth of ,hynodon1 as well as the permanent dentition of the ancestral genera1 show that the anterior cusp was composed of the two external cusps of the primitive tritubercular tooth fused into one and that the trenchant ridge was a superadded element4 ,the fourth upper premolar was a sectorial like that of the ,fissipedia1 but of an unfinished1 ineffective sort4 ,the third lower molar was very similar in shape to the carnassial of the cats and was composed of only two large1 thin and trenchant cusps1 which made a shearing blade1 having lost the inner cusp of the primitive triangle and the heel4 ,the first and second molars were like the third except in size and in retaining a vestige of the heel4 ,the premolars were large and massive1 almost hyena-like1 which suggested the generic name4 ,the canines were prominent and strong4 ,illustration3 ,,fig4 #bgg4--;,hynodon horridus1 a ,white ,river creodont3 in the background1 ,leptomeryx evansi4 ,restored from skeletons in the ,american ,museum of ,natural ,history4 ,the skull1 as in almost all creodonts1 was relatively very large1 but in the various species there was considerable difference of shape2 more commonly it was long and narrow1 with elongate jaws1 and was quite wolf-like in appearance1 but in some of the species it was shorter and wider4 ,the brain-case was more capacious and the brain more richly convoluted than in any other known creodont1 but the sagittal and occipital crests were very prominent4 ,the neck was rather short1 not equalling the head in length1 the body elongate and the loins very muscular2 the tail was fairly long and thick1 but much less so than in most creodonts4 ,the limbs were short and1 in most of the species1 quite slender1 though in some they were much stouter2 the primitive features1 such as the third trochanter of the femur1 the epicondylar foramen of the humerus1 the separate scaphoid1 lunar and central in the carpus1 were retained4 ,the feet had five digits arranged in spreading fashion and were probably semi-digitigrade2 the claws were so thick and blunt that they could hardly have served in seizing prey4 ,illustration3 ,,fig4 #bgh4--,skeleton of ,hynodon4 ,american ,museum4 ,the restoration gives the animal quite a near resemblance to the modern hyenas and perhaps errs in making the likeness so close4 ,from the whole structure of the skeleton and the form of the claws1 it may be inferred that ,hynodon was not a swift runner or very efficient in the capture of prey4 ,while probably savage fighters1 they doubtless subsisted chiefly as carrion-feeders and scavengers4 ,illustration3 ,,fig4 #bgi4--,lower teeth1 right side1 of hynodontids4 ,a1 ,sinopa4 ,b1 ,tritemnodon4 ,c1 ,pterodon4 ,d1 ,hynodon4 ,x1 ,oxyna4 ,the dotted line connects the first molar of each1 lost in ,pterodon4 ,see explanation of ,fig4 #bhj4 7,after ,matthew47 ,another doubtfully distinct genus1 ,hemipsalodon1 was so closely like1 if not identical with1 the much better known ,european ,pterodon1 that the latter may be taken in place of it4 ,pterodon was similar in most respects to ,hynodon1 but distinctly less advanced1 and though not the ancestor of the latter1 serves to connect it with the older members of the series4 ,pterodon did not1 so far as we know1 penetrate ,north ,america south of the ,canadian border1 occurring in the lower ,white ,river of ,alberta4 ,in this genus the upper molars retained a large internal cusp1 and the third molar1 though small and not sectorial1 had not been lost2 the two external cusps were connate1 but not completely fused together and the posterior ridge was not so well developed as in ,hynodon1 nor was the fourth upper premolar so nearly a carnassial4 ,the lower molars were shearing blades1 but distinct vestiges of the heel remained4 ,so far as they are known1 the skull and skeleton resembled those of ,hynodon4 ,illustration3 ,,fig4 #bhj4--,upper teeth of hynodontids1 right side1 showing the grinding surface4 ,a1 ,sinopa1 ,wasatch and ,bridger4 ,b1 ,tritemnodon1 ,bridger4 ,c1 ,pterodon1 upper ,eocene and lower ,oligocene of ,europe4 ,d1 ,hynodon1 ,white ,river4 ,the dotted line connects the first molar of each4 ,for comparison is added ,x1 ,oxyna1 one of the ,oxynid4 ,c and ,d are much larger than the others1 but all1 except ,x1 are reduced to the same length4 7,after ,matthew47 ,hynodon and ,pterodon were evidently derived from a group of small creodonts which1 in the lower and middle ,eocene1 were spread all over the northern hemisphere1 but it is not yet possible to select from the crowd of allied genera those which formed the actual steps of descent4 ,these small animals were numerous and varied and are far better known in ,north ,america than in ,europe and it is not at all improbable that some of the lower ,eocene genera migrated to the ,old ,world and there gave rise1 among other forms1 to ,hynodon and ,pterodon1 which eventually returned to the land of their earlier ancestry4 ,if confirmed1 this will be an exceptionally interesting case of back and forth migration4 ,however that may be1 the ,american ,eocene genera1 ,sinopa and ,tritemnodon1 illustrate very well the ancestry of the ,oligocene genera1 as they must have been similar to the actual progenitors4 ,illustration3 ,,fig4 #bha4--,tritemnodon agilis1 a primitive hynodont1 ,bridger stage4 ,restored from a skeleton in the ,american ,museum4 ,the first and most obvious difference from the ,oligocene genera was the very much smaller size of the animals1 few of the ,eocene forms equalling a fox in height4 ,the teeth were unreduced in number1 and there were three pairs of carnassials4 ,the first and second upper molars were not far removed from the primitive tritubercular form1 but the two external cusps were close together and a small posterior cutting ridge was present2 the third molar was progressively reduced in size4 ,the three lower molars were carnassials of a rather imperfect kind and the first was the smallest of the series2 the two outer cusps of the anterior primitive triangle formed the shearing blade and there was a basin-shaped heel4 ,the skull was long1 narrow and low and the cranial portion1 despite the very small brain-case1 was especially elongate1 though face and jaws were also long2 the sagittal crest was very prominent4 ,the neck was of moderate length1 the body long and slender and the tail extremely long4 ,the short and delicate limbs were of very primitive character1 but the radius had already lost the power of rotation2 the feet had five spreading digits1 armed with sharp claws4 ,the hynodont relationships of these small animals are obvious in every part of their structure and yet1 as would be expected1 they were far less specialized4 ,probably1 too1 they were more active and successful hunters of prey1 the smaller mammals and birds1 less given to carrion-feeding4 ,the line probably originated in the ,oxyclnid of the ,paleocene4 #f4 ,oxynid ,the genera of this family had such feline characters that more than one writer has been misled into the belief that they were the ancestors of the cats4 ,in this family there were two pairs of sectorial teeth1 of which the larger pair was composed of the first upper and second lower molar1 the smaller pair of the fourth upper premolar and first lower molar1 as in the fissipedes4 ,of the three phyla within the family1 the most specialized one ran a brief career1 through the ,wasatch1 ,wind ,river and ,bridger1 and then died out4 ,the terminal member of this series1 the ,bridger genus ,patriofelis1 had a skull as large as that of a lion1 but the rest of the skeleton was not so large in proportion4 ,the teeth were considerably reduced in number1 the formula being3 i 8_/#b1 c #a_/a1 p #c_/c1 m #a_/b1 a loss of at least twelve from the primitive total of #dd4 ,the single upper molar was a large sectorial1 which was formed much as in the hynodonts1 the two external cusps connate1 but not indistinguishably fused together1 and a long1 trenchant ridge behind1 while the inner cusp had almost vanished4 ,the second lower molar was very cat-like2 its cutting blade was formed of two shearing cusps2 of the inner cusp no trace was left1 and of the heel merely a vestige4 ,the first lower molar was smaller and less specialized1 since it retained a small internal cusp and quite a large heel4 ,illustration3 ,,fig4 #bhb4--,patriofelis ferox1 ,bridger stage4 ,restored from a skeleton in the ,american ,museum4 ,the skull was very large and massive1 with elongate cranium and shortened face1 the muzzle broad and abruptly truncate1 not tapering2 the brain-case was exceedingly small1 with very long and prominent sagittal crest2 the zygomatic arches were extremely heavy and curved outward boldly1 so that the head was very wide1 notwithstanding the absurdly small brain-case4 ,the lower jaw was very deep and heavy and the chin abruptly rounded1 with almost vertical front4 ,the very unusual massiveness of the zygomatic arches and the great development of the crests and ridges for the attachment of the jaw-muscles1 and the short1 heavy lower jaw1 all indicate a degree of power in the biting and shearing apparatus such as occurred in no other known creodont4 ,the neck was of medium length1 while the body1 though actually elongate1 was rather short as compared with most other creodonts2 the loins were very heavy and must have been extremely powerful in the living animal2 in this region the articulations between the successive vertebr were more complex than in any other member of the suborder2 resembling the structure found in certain artiodactyls4 ,the ribs were long and thick1 the chest deep and capacious4 ,even for a creodont1 the tail was long and uncommonly thick4 ,illustration3 ,,fig4 #bhc4--,right pes of ,patriofelis ferox4 ,cal41 calcaneum4 ,as41 astragalus4 ,cb41 cuboid4 ,n41 navicular4 ,cn4 #a1 #b1 #c1 internal1 middle and external cuneiforms4 7,after ,wortman47 ,the limbs1 especially the anterior pair1 were short and very stout2 the humerus had an immensely developed deltoid ridge1 which extended down for two-thirds the length of the shaft1 and a very prominent supinator ridge2 the fore-arm bones1 particularly the ulna1 were heavy and the radius had but a limited power of rotation4 ,the feet were short and broad1 with five complete1 spreading toes1 ending in thick and blunt-pointed claws4 ,patriofelis was by far the most formidable of the ,bridger ,carnivora and1 with the exception of ,harpagolestes1 the largest4 ,its appearance must have been very curious1 judged from the modern standpoint1 with its disproportionately large1 broad and rounded1 leonine head1 thick body and long1 extremely heavy tail4 ,the short1 powerful limbs and broad feet must have given it something of the appearance of an otter4 ,as in the case of so many other creodonts1 the combination of characters in the skeleton makes the question of habits a very puzzling one4 ,the teeth had a form suited only to seizing and devouring prey1 but the short legs and feet were not at all adapted to the swift movements1 whether by long-continued running1 or by stealthy approach and sudden leap1 which are required in capturing agile prey1 while the blunt claws could have rendered no service in holding a struggling creature4 ,the form of the humerus and fore foot suggests burrowing habits1 but it seems most unlikely that so large an animal could have lived in any such fashion4 ,terrestrial1 arboreal and aquatic modes of life have all been suggested1 and1 all things considered1 perhaps the least improbable conclusion is that ,patriofelis was more or less aquatic and preyed chiefly upon the fishes and turtles with which the ,bridger waters abounded4 ,this hypothesis of ,dr4 ,wortman's is supported by the otter-like form of the animal4 ,whatever the principal kind of food was1 it must have been something that greatly abraded the teeth1 which in old animals were mere stumps4 ,illustration3 ,,fig4 #bhd4--,oxyna lupina1 ,wasatch stage4 ,restored from a skeleton in the ,american ,museum4 ,the ,wind ,river representatives of the series are known only from fragments1 which1 so far as they go1 are not separable from ,patriofelis4 ,on the other hand1 the ,wasatch genus1 ,oxyna1 is fairly well understood4 ,this genus was very like its ,bridger successor1 but differed from it in just such ways as would be expected in an immediately ancestral form1 that is to say1 in smaller size and less advanced specialization4 ,the number of teeth was not so far diminished3 i #c_/c1 c #a_/a1 p #d_/d1 m #b_/b1 #b #dj2 the carnassial teeth were the same1 but they were less effective2 the fourth upper premolar and first upper molar had large inner cusps1 and in the latter the postero-external trenchant ridge was shorter4 ,the second upper molar1 lacking in ,patriofelis1 was a transversely placed ridge1 which engaged the heel of the second lower molar4 ,the latter tooth1 though larger than the first molar1 was much less completely trenchant than in ,patriofelis and retained a small internal cusp and quite large heel4 ,the skull resembled that of the ,bridger genus1 but the face was not so much shortened1 the zygomatic arches were not so widely expanded or so massive1 the lower jaw was not so heavy1 nor the chin so steep4 ,the body was relatively longer and more slender1 the ribs being thinner and the chest shallower2 the tail was even longer1 but not nearly so thick4 ,the articulations of the lumbar vertebr were less complex4 ,except for their greater length and slenderness the limbs and feet were nearly identical with those of ,patriofelis4 ,in appearance1 ,oxyna must have been merely a smaller1 lighter and less powerful variant of the ,bridger genus1 and1 no doubt1 its habits of life were substantially the same2 but in the details of structure were many minor differences1 all of them in the direction of greater primitiveness in the more ancient animal4 ,the second phylum of the family was represented in the ,uinta and ,bridger stages by a group of small species1 which were survivors of still more ancient and primitive progenitors of the family4 ,in the typical genus1 ,limnocyon1 the dental formula was the same as in ,oxyna3 i #c_/c1 c #a_/a1 p #d_/d1 m #b_/b1 but the first upper molar had its two external cusps well separated and a much lower posterior cutting ridge1 while the inner cusp was much larger4 ,the second upper molar1 though transversely placed1 had all the elements of the primitive tritubercular tooth1 the pattern from which all the varied types of creodont upper molars were derived by the addition or suppression of parts4 ,the two lower molars were very primitive1 having a high anterior triangle of three cusps1 forming an imperfect shearing blade1 and a low heel4 ,this dentition was on nearly the same plan as that of the small1 contemporary hynodonts1 but the emphasis of development1 so to speak1 was differently placed4 ,in the hynodonts there were three pairs of sectorials and the best-developed pair was made up of the second upper and third lower molar2 while in ,limnocyon the third molar was lost1 and there were but two pairs of sectorials1 of which the largest pair was the first upper and second lower molar1 as was also true of ,oxyna and ,patriofelis4 ,the skull of ,limnocyon had a much longer facial region1 and more elongate and slender jaws than in the last-named genera1 and the feet must have been quite different1 with less spreading digits4 ,limnocyon thus tends to indicate a common origin for the oxynids and hynodonts1 though these common ancestors are still unknown4 ,a very interesting genus of this series1 ,machairoides1 of the ,bridger1 shows another imitation of the cats1 the flanges of the lower jaw indicating sabre-like upper canines4 ,another genus1 ,palonictis1 of the ,wasatch1 found also in ,france1 is sometimes referred to the ,oxynid and sometimes made the type of a distinct family1 but is too incompletely known for final reference4 ,it had the same number of teeth as ,oxyna1 but the principal pair of carnassials was the fourth upper premolar and first lower molar1 as in the ,fissipedia1 the first upper and second lower molar forming the subsidiary pair4 ,the first upper molar was hardly sectorial at all2 its two outer cusps were long1 sharp-pointed cones1 and the posterior cutting ridge was a mere tubercle4 ,the skull had a short1 cat-like face4 ,the genus left no successors4 99 99 99 99 99 ,this concludes the long story of the ,carnivora1 so far as it has been recovered from the rocks4 ,incomplete as it is1 and full of unsolved problems1 it yet enables us to follow1 somewhat vaguely1 but with a general kind of accuracy1 the development of the various modifications which characterized the different families and genera of the group4 ,the more ancient and primitive suborder1 the ,creodonta1 made its first recorded appearance in the lower ,paleocene and was1 no doubt1 derived from ,mesozoic ancestors1 which cannot yet be distinguished among the very imperfectly understood mammals of that era4 ,in the upper ,paleocene1 if not before1 the creodonts had spread over the northern hemisphere and had begun to diverge into a number of families1 which continued to diverge more and more widely throughout the ,eocene epoch1 as they became more specialized and adapted to different habits of life4 ,from the most primitive group1 represented more or less accurately by the ,oxyclnid1 may be traced the several lines of diverging adaptations incorporated in the various families1 some of which had become distinctly recognizable in the lower ,paleocene1 others in the upper1 while all were in existence in the lower ,eocene4 ,in one series1 the ,mesonychid1 the upper teeth underwent comparatively little change1 while the lower ones lost the inner cusps1 but no carnassials were formed4 ,the face and jaws were elongated and the limbs and feet became adapted to cursorial habits1 and the more advanced genera had four-toed1 completely digitigrade feet1 with blunt1 almost hoof-like claws4 ,a second series1 the ,arctocyonid1 likewise failed to develop sectorial teeth1 the molars becoming quadritubercular1 with many accessory tubercles1 and assuming a bear-like or pig-like pattern1 while the premolars were reduced in size4 ,the pentadactyl feet had sharp claws4 ,in the ,oxynid two pairs of carnassial teeth were formed1 of which the larger and more effective pair were the first upper and second lower molar1 the smaller pair the fourth upper premolar and first lower molar4 ,the teeth were diminished in number1 first by the loss of the last molar1 then the suppression of the first premolar and finally by that of the third incisor and second upper molar2 the remaining teeth were enlarged4 ,the upper carnassial molar 7the first7 was formed by the approximation and partial fusion of the two external cusps and the addition of a trenchant ridge behind these1 and by the reduction and eventual loss of the internal cusp1 thus becoming more exclusively shearing in function4 ,the second lower molar also lost the inner cusp and the heel1 becoming remarkably cat-like in form2 the first was similar1 but less simplified4 ,the face and jaws were greatly shortened1 which1 with the widely expanded zygomatic arches1 gave the head a very cat-like appearance4 ,the body and tail were long1 the limbs short and thick1 and the feet had spreading toes and blunt claws4 ,save for a notable increase in size and muscular power1 the oxynids showed but little change within the family4 ,the ,hynodontid differed from the oxynids in the retention of all or nearly all the teeth and in having three pairs of sectorials1 of which the largest pair was the second upper and third lower molar1 but resembled them in the mode of forming these sectorials and in the cat-like form of the inferior ones4 ,although the actual line of descent was not through these genera1 the series1 ,sinopa--,tritemnodon--,pterodon--,hynod on1 extending from the lower ,eocene into the ,oligocene1 displays perfectly the successive steps in the transformation of the teeth4 ,the skull underwent a corresponding series of changes1 ending in long-faced1 long-jawed1 wolf-like forms1 with larger brain-case than in any other creodonts4 ,the elongated form of body was retained1 but the tail was reduced to moderate proportions4 ,the limbs and feet did not change greatly1 except in size and in the greater bluntness of the claws4 ,the ,miacid1 if not actually referable to the ,fissipedia1 at least anticipated them in the mode of carnassial development4 ,the upper molars changed very little from the primitive tritubercular plan1 but the fourth upper premolar was enlarged and acquired a trenchant ridge behind the original single outer cusp4 ,the lower molars were at first all alike1 except in size1 the first being the largest2 they had the primitive pattern common to the earlier members of nearly all the creodont families1 of an elevated anterior triangle of three subequal cusps and low1 basin-like heel4 ,the first molar grew larger in the successive genera and1 by the enlargement of the two external cusps of the primitive triangle and reduction of the inner one1 gradually became an efficient sectorial1 the fourth upper premolar keeping pace with it4 ,in proportion as the first lower molar was elaborated1 the second and third were reduced in size and the anterior triangle was lowered to the level of the heel1 these teeth thus becoming tubercular4 ,all the ,miacid were small animals1 none attaining the stature of a fox1 though some had heads as large4 ,from this family1 as was pointed out above1 probably arose all of the ,fissipedia1 the history of which it is needless to repeat4 ,,chapter ,,xv ,,history ,,of ,,the ,,primates ,this order embraces the lemurs1 monkeys1 man-like apes and ,man1 though in the general account ,man will be omitted from consideration4 ,the ,primates are clothed in dense fur or shaggy hair4 ,the teeth are always low-crowned and rooted and reduced in number1 the incisors generally to #b_/b and the premolars to #c_/c-b_/b2 the molars are trituberculate or quadrituberculate4 ,the cranium is unusually capacious and the orbit is entirely encircled in bone4 ,the tail varies much in length and may be entirely wanting4 ,the bones of the fore-arm and lower leg are separate and the radius has much freedom of rotation1 in correspondence with the grasping power of the hand4 ,the pes is also a grasping organ and1 with few exceptions1 the thumb and great toe are opposable to the other digits2 the bones of the wrist do not cossify and frequently the central is present4 ,the feet are plantigrade and almost always pentadactyl and1 with a few exceptions1 have neither claws nor hoofs1 but flat nails2 the ungual phalanges are correspondingly modified and do not taper toward the free end1 but expand at the tip4 ,the ,primates are characteristically arboreal in habit1 but a few1 such as the baboons1 have become secondarily adapted to a terrestrial mode of life4 ,they inhabit at present all the tropical regions of both hemispheres1 ,australia excepted4 ,extra-tropical ,north ,america has no existing member of the order and1 so far as we know1 has had none since the ,eocene epoch4 ,the most important of the genera of the western hemisphere are listed below4 ,suborder ,,lemuroidea4 ,lemurs ,i4 ,,notharctid4 ,pelycodus1 low4 and mid4 ,eoc4 ,notharctus1 ,eoc4 ,,ii4 ,,anaptomorphid4 ,anaptomorphus1 low4 and mid4 ,eoc4 ,omomys1 mid4 ,eoc4 ,hemiacodon1 do4 ,suborder ,,anthropoidea4 ,monkeys1 ,apes1 ,man ,section ,,platyrrhina ,,iii4 ,,hapalid4 ,marmosets4 ,hapale4 ,pleist4 and ,rec4 ,midas1 ,rec4 ,,iv4 ,,cebid4 ,south ,american ,monkeys4 ,cebus1 ,pleist4 and ,rec4 ,alouatta1 ,howling ,monkeys1 ,pleist4 and ,rec4 ,ateles1 ,spider ,monkeys4 ,pithecia1 ,sakis4 ,cacajao1 ,uakaris4 ,nyctipithecus1 ,douroucoulis4 ,eriodes1 ,pleist4 ,homunculus1 ,santa ,cruz4 ,pitheculus1 do4 ,the existing ,primates are divided into two suborders1 ,lemuroidea and ,anthropoidea1 which are quite clearly distinguished from each other1 but the fossil forms largely efface the distinction4 ,,suborder ,,lemuroidea4 ,,lemurs ,the name ,lemur1 which ,linnus gave to a genus of this suborder1 signifies in ,latin a spectre or ghost and was probably suggested by the very strange appearance and nocturnal habits of these curious creatures4 ,the term has been adopted as the ,english name for the group1 as there was no vernacular word for it4 ,the lemurs are very obviously the more primitive division of the ,primates4 ,omitting for the present the extinct forms1 the dental formula is usually3 i #b_/b1 c #a_/a1 p #c_/c1 m #c_/c1 #b #cf2 the upper canine is a long1 sharp1 dagger-like tooth1 but the lower one1 in nearly all of the genera1 is like an incisor and its place is taken by the anterior premolar2 the premolars are simple1 compressed and trenchant and the upper molars tritubercular4 ,the skull usually has a long and tapering facial portion1 so that the living head has some resemblance to that of a raccoon4 ,the orbits almost always have a more or less lateral presentation1 instead of being directed forward1 as they are in the ,anthropoidea2 they are encircled in bone1 but are not walled in by a bony funnel2 the lachrymal bone is extended on the face and the foramen is outside of the orbit4 ,the hind legs are longer than the fore2 the humerus retains the epicondylar foramen and the femur has a third trochanter2 the feet are plantigrade1 almost always five-toed1 with opposable thumb and great toe1 and having a varying proportion of flat nails and sharp claws4 ,the brain is of a primitive type and not much convoluted4 ,all the existing and most of the fossil lemurs are small animals1 some quite minute1 and only in the ,pleistocene of ,madagascar have large ones been found4 ,they are chiefly nocturnal and arboreal in habits1 and feed upon fruit and leaves1 but vary their diet with insects1 small reptiles1 birds and eggs4 ,their present geographical distribution is very remarkable2 more than two-thirds of the existing species are confined to ,madagascar2 the others are in tropical ,africa1 southern ,asia and the ,asiatic islands1 as far east as ,celebes and the ,philippines4 ,in the ,eocene epoch they extended all over the northern hemisphere1 but have not been found in any subsequent formation outside of their present range4 ,lemurs occurred in the ,uinta stage1 but were much more abundant in the ,bridger1 of which the best-known genus is ,notharctus4 ,these ,eocene forms did not have the aberrant peculiarities of the modern lemurs1 but departed less from the primitive stock common to both of the suborders4 ,in ,notharctus the dental formula was3 i #b_/b1 c #a_/a1 p #d_/d1 m #c_/c1 #b #dj1 the dentition being reduced only to the extent of losing one incisor on each side above and below2 the lower canine was not incisiform nor had the anterior premolar taken its place2 the upper molars were quadritubercular1 and in the lower ones the anterior triangle was hardly higher than the heel4 ,the two halves of the lower jaw were cossified at the symphysis1 and the femur had lost the third trochanter4 ,it is not likely that ,notharctus was ancestral to any of the existing lemurs1 but may have been to the numerous forms of the ,european upper ,eocene4 ,the ,wasatch genera are known from very fragmentary material1 but it suffices to show that some of the genera1 at least 7e4g4 ,pelycodus71 were decidedly more primitive than those of the ,bridger4 ,the incisors had already been reduced to #b_/b1 the well-nigh universal formula among the ,primates2 the upper molars were tritubercular1 but with a minute fourth cusp beginning to appear1 and in the lower molars the anterior triangle was elevated above the heel4 ,the two halves of the lower jaw were separate4 ,the ,paleocene has yielded nothing that can be positively referred to the ,primates1 but there was a group of genera 7e4g4 ,indrodon71 known only from jaws and teeth1 which have been variously assigned to the lemurs and the ,insectivora and may have belonged to either order1 or have represented the transition between them4 ,this very uncertainty is in itself a significant fact1 for it is another of the many examples of the way in which1 at that early period1 the mammalian orders were so approximated that it is often very difficult to distinguish them4 ,it was stated above that the distinction between existing lemurs and anthropoids was a very clear one1 but to this statement there is one partial exception4 ,the curious little ,tarsier 7,tarsius spectrum71 an animal about the size of the ,grey ,squirrel1 an inhabitant of the ,malay ,archipelago1 is thus described by ,mr4 ,beddard3 8,the ears are large and the eyes are extraordinarily developed4 ,the fingers and toes terminate in large1 expanded disks and are furnished with flattened nails1 except on the second and third toes1 which have claws4 ,the tail is longer than the body and tufted at the end4444 ,the ,tarsiers are nocturnal and particularly arboreal2 they live in pairs1 in holes in tree stems and are mainly insectivorous in their food4444 ,like so many ,lemurs1 this animal is held in superstitious dread1 which is the result of its most weird appearance40#ac ,the skull is more anthropoid in character than is that of any other lemur1 the face being greatly shortened1 the cranium enlarged and the orbit not merely encircled in a bony rim1 but with a thin posterior wall of bone4 ,there are also structural features in the soft parts1 which are more anthropoid than lemuroid4 ,illustration3 ,,fig4 #bhe4--;,head of monkey-like lemur 7,anaptomorphus homunculus7 from the ,wasatch4 ,restored from a skull in the ,american ,museum4 ,the particular interest which ,tarsius possesses for the student of ,american mammals is its resemblance to the ,wasatch genus ,anaptomorphus1 the type of a family which was abundant and varied in the lower and middle ,eocene4 ,this genus was remarkably advanced in view of its great antiquity4 ,the dental formula was3 i #b_/b1 c #a_/a1 p #c_/c-b1 m #c_/c1 #b #cd-cf2 in the upper jaw the premolars were bicuspid and the molars tritubercular1 while the lower premolars were simple4 ,the face was very much shortened2 the orbits were very large and encircled in bone1 but without the posterior wall4 ,this produces a decided likeness to the ,tarsier and is no doubt indicative of nocturnal habits4 ,the cranium was remarkably large1 and no other ,wasatch animal had a brain-case so capacious in proportion to its size4 ,a lemurine character was the position of the lachrymal foramen outside of the orbit4 ,the two halves of the lower jaw were separate4 ,it is hardly likely that these ,american lemurs were the actual ancestors of the anthropoids1 but they closely represent what those ancestors must have been4 ,,suborder ,,anthropoidea4 ,,monkeys1 ,,apes1 ,,man ,the specifically human characters will be omitted in defining the suborder4 ,the ,anthropoidea are plantigrade1 usually arboreal and pentadactyl1 with opposable thumb and great toe and thus the pes is like a hand1 hence the term 8,quadrumana0 formerly given to the apes and monkeys4 ,except in the ,south ,american marmosets 7,hapalid7 all of the digits have nails4 ,the canines are generally more or less tusk-like1 projecting above 7or below7 the level of the other teeth2 the premolars mostly have two tubercles1 like the human bicuspids1 the upper molars have three1 or more commonly four1 cusps and the lower1 four or five4 ,save in the baboons1 the skull has a very short muzzle and a very large cranium1 the capacity of which is relatively greatest in the large apes2 the brain is large and complexly convoluted4 ,the orbits present directly forward and are deep1 funnel-shaped cavities for the lodgment of the eyeballs1 a thin bony wall completely enclosing them externally and posteriorly4 ,the lachrymal bone and its foramen are within the edge of the orbit2 the nasal bones are short and have a nearly vertical position4 ,the two frontal bones are early fused into one and usually there is no sagittal crest2 the two halves of the lower jaw are cossified at the symphysis4 ,the tail is extremely variable in length and may be three times as long as the body1 or entirely absent4 ,the fore and hind legs are sometimes of nearly equal length1 but far more frequently the anterior pair are much the longer4 ,the length of the legs in proportion to that of the body is very different in the different families4 ,the humerus is much like that of ,man and has no epicondylar foramen2 the radius has a very complete movement of rotation2 the femur never has the third trochanter and the lower leg bones are always separate4 ,the thumb is more or less opposable to the other digits1 except in the marmosets1 but never so perfectly as in ,man2 the great toe is also opposable1 but shorter than the other digits4 ,the ,anthropoidea are divisible into two sections1 the ,catarrhina1 characteristic of the ,old ,world1 and the ,platyrrhina1 confined to the ,new4 ,in the ,catarrhina1 or ,old ,world apes and monkeys1 the dental formula is the same as in ,man3 i #b_/b1 c #a_/a1 p #b_/b1 m #c_/c1 #b #cb2 the nostrils are close together and the tympanic bull have tubular entrances4 ,many1 but not all1 have cheek-pouches opening into the mouth4 ,the tail is never prehensile and1 except in most of the large1 man-like apes 7,simiid71 there are naked callosities on the buttocks4 ,with these ,old ,world forms we have no further concern1 though it may be noted in passing that ,dr4 ,schlosser has discovered in the ,oligocene of ,egypt certain monkeys 7,parapithecus7 which he thus describes3 8,the number and structure of the teeth1 character of the jaws and bodily size make complete the transition from the ,anaptomorphids and ,tarsiids to the ,simiids40 ,section ,platyrrhina4 ,south ,american ,monkeys ,in these animals the nostrils are separated by a broad septum1 and there are always three premolars above and below 7p #c_/c74 ,the tail is frequently prehensile and serves as a fifth limb1 being capable of supporting the whole weight of the body4 ,there are no cheek-pouches and no callosities1 and the tympanic bull have no bony tubes leading into them4 ,the thumb is but partially1 or not at all1 opposable and in some genera is absent4 ,the ,new ,world monkeys are1 in general1 smaller and lighter than those of the eastern hemisphere2 there are no very large ones and they are all arboreal and are confined to the forested parts of the ,neotropical region1 except the ,west ,indies1 which have none4 ,the marmosets 7,hapalid71 the first of the two families into which the ,platyrrhina are divided1 are little creatures1 no longer than squirrels1 with long1 non-prehensile tails4 ,they are characterized by the dental formula3 i #b_/b1 c #a_/a1 p #c_/c1 m #b_/b1 #b #cb1 and are the only ,primates which have no third molar above or below4 ,the thumb is not opposable1 though quite long1 and the hallux1 or great toe1 is very small2 they are thus deficient in grasping power4 ,instead of the flat nails common to all the other ,anthropoidea1 they have long1 sharp claws4 ,all other ,south ,american monkeys are included in the family ,cebid which1 in turn1 is divided into four subfamilies4 ,it is not necessary to consider these or do more than cite a few illustrative examples4 ,illustration3 ,,fig4 #bhf4--;,common ,marmoset 7,hapale74--,by permission of ,w4 ,l4 ,berridge1 ,london4 ,illustration3 ,,fig4 #bhg4--,sapajou 7,cebus74--,by permission of the ,new ,york ,zological ,society4 ,some twenty species of the genus ,cebus are distributed from ,central ,america to ,paraguay2 they have long1 prehensile tails completely covered with hair1 and well-developed thumbs4 ,the monkeys of this genus are familiar to every one1 as they are largely used by organ-grinders4 ,the spider-monkeys 7,ateles7 are so called because of the great length and slenderness of their limbs2 the tail is very long and perfectly prehensile1 naked on the lower side near the end1 which improves its grasping power4 ,the hand has lost the thumb1 but is used very effectively as a hook4 ,the species1 ten or more in number1 have a wider range than those of ,cebus and extend from ,uruguay to ,mexico4 ,the howling monkeys 7,alouatta1 more commonly1 but improperly1 called ,mycetes7 are gifted with most unusual vocal powers4 ,mr4 ,bates says of them3 8,morning and evening the howling monkeys make a most fearful and harrowing roar40 8,the brief evening chorus of animals then began1 the chief performers being the howling monkeys1 whose frightful unearthly roar deepened the feeling of solitude which crept on as darkness closed around us40#ad ,the tremendous volume of sound which these small creatures are able to produce is due to a resonating apparatus1 formed by the great inflation of one of the hyoid bones 7see p4 #fg71 normally the bony support of the tongue4 ,the tail is long and prehensile1 with the end naked beneath2 the thumb is well developed4 ,the sakis 7,pithecia7 have long and non-prehensile tail and complete thumb4 ,the species of this genus have a remarkable kind of distribution1 which is rare among mammals1 though not infrequent for insects and birds4 ,each species is limited to a definite area of forest along the ,amazon and its tributaries1 which it occupies to the exclusion of the others4 ,the uakaris 7,cacajao7 are distinguished by the tail1 which is much shorter than in any other of the ,cebid4 ,finally1 may be mentioned the nocturnal douroucoulis 7,nyctipithecus71 which have long1 non-prehensile tail and well-developed thumb4 ,mr4 ,bates describes them thus3 8,a third interesting genus of monkeys1 found near ,ega1 are the ,nyctipitheci1 or night apes1 called ,ei- by the ,indians4444 ,they sleep all day long in hollow trees and come forth to prey on insects and eat fruits only at night4 ,they are of small size1 the body being about a foot long and the tail fourteen inches1 and are thickly clothed with soft gray and brown fur1 444 and the eyes are large and yellowish in colour1 imparting the staring expression of nocturnal animals of prey40#ae ,the ,brazilian caverns have preserved the remains of many ,pleistocene monkeys belonging to existing ,south ,american genera1 and even several modern species are represented1 while others are extinct4 ,there is also one extinct genus 7,eriodes71 a larger animal than any of the existing ,neotropical monkeys4 ,the ,pampean deposits of ,argentina1 on the other hand1 have yielded no remains of ,primates1 nor is this surprising1 for the ,pampas would seem to have been open plains in the ,pleistocene1 as they are to-day4 ,between the ,pleistocene and the ,santa ,cruz ,miocene there is a long gap in the history4 ,it is true that some bones have been found in the ,pliocene of ,monte ,hermoso which have been referred to the ,primates1 but they are too few and imperfect to be of any real assistance in the inquiry4 ,in the ,santa ,cruz beds fossil monkeys are very rare1 but that they were present in ,patagonia at all1 is strong evidence that the climate was then far milder than it is at present4 ,these were essentially members of the modern family ,cebid4 ,the best-known genus1 ,homunculus1 retained a few primitive characters1 which the existing genera have lost4 ,for example1 the premolars were relatively smaller and of simpler form and the humerus had the epicondylar foramen1 though the femur no longer had the third trochanter4 ,the radius was very modern in form and evidently could rotate freely upon the humerus4 ,no monkeys have been found in the ,deseado formation1 though too much stress should not be laid upon this fact1 because of the general scarcity of small animals in those beds4 ,but the same is true of the still more ancient stages2 despite an abundant and varied fauna of small mammals1 they have yielded no ,primates1 nor anything which could be seriously regarded as ancestral to them4 ,the facts are essentially the same as we have found them to be with reference to the ,south ,american rodents and insectivores4 ,all three of these orders appeared suddenly and unheralded in the ,deseado 7,rodentia7 or ,santa ,cruz 7,insectivora1 ,primates71 and all of them were allied to ,african or ,european rather than to ,north ,american types4 ,if we may assume the existence of a land-connection with ,africa to account for the remarkable distribution of the hystricomorph rodents1 the same connection will equally well explain the introduction of the ,primates into ,south ,america4 ,concerning the relations of the ,old and ,new ,world monkeys1 ,mr4 ,beddard remarks3 8,not only are these two groups of the ,primates absolutely distinct at the present day1 but they have been1 so far as we know1 for a very long time1 since no fossil remains of ,monkeys at all intermediate have been so far discovered4 ,this has led to the suggestion that the ,monkeys are what is termed diphyletic1 i4e41 that they have originated from two different stocks of ancestors4 ,it is hard1 however1 to understand on this view the very great similarities which underlie the divergences that have just been mentioned4 ,but1 on the other hand1 it is equally hard to understand how it is that1 having been separated from each other for so long a period1 they have not diverged further in structure than they have40#af ,the fossil monkeys of the ,santa ,cruz beds show that1 as a matter of fact1 the ,south ,american ,primates have undergone little change in the essentials of structure since that remote period1 and thus is removed this objection to the conclusion that the ,platyrrhina and ,catarrhina were derived from a common ancestry4 ,in a certain sense also1 the discovery of ,parapithecus in ,egypt has diminished the gap between these two sections of the ,anthropoidea4 ,the evidence1 though by no means conclusive1 is distinctly in favour of the derivation of the ,south ,american monkeys from ,old ,world ancestors4 ,the ,catarrhina have developed and advanced from the point of divergence far more than have the ,south ,american forms1 which have changed relatively little since their invasion of the ,neotropical region4 ,so far as has been ascertained1 ,south ,america never had any of the lemurs4 ,,man ,,in ,,the ,,western ,,hemisphere ,though to most people this is undoubtedly the most interesting chapter of all the mammalian history1 little space can be given to it here1 for the reason that the subject belongs rather in the domain of ,anthropology and ,ethnology than in that of ,palontology4 ,there can be no question that ,man originated in the eastern hemisphere and at a very remote period2 abundant remains of his handiwork and of himself have been found in ,europe as far back as the early ,pleistocene1 and recent discoveries in ,england have increased the already known length of the human habitation of ,europe4 ,so primitive and ape-like were some of these ancient men that they have been named as species 7,homo neanderthalensis and ,h4 heidelbergensis7 distinct from the existing ,h4 sapiens4 ,recently discovered and very ancient remains in ,england have even been referred to a separate genus1 ,eoanthropus4 ,as has been repeatedly pointed out in the preceding chapters1 ,america received numerous successive waves of mammalian immigrants during the ,pleistocene epoch1 at a time when there was a broad land-connection between ,north ,america and ,asia1 where now is ,bering ,strait2 and to this late connection is due the fact that the ,boreal zone of ,north ,america 7see p4 #aej7 is zologically a part of the ,old ,world and forms a division of the ,holarctic region4 ,now1 there is no known reason why ,man1 whose powers of dispersal are so superior to those of any other mammal1 should not have accompanied these migrations1 and it is entirely possible that he actually did so1 but the fact has not been demonstrated4 ,it is true that discoveries of ,pleistocene ,man have been frequently reported from both ,north and ,south ,america1 but these have not stood the test of critical examination1 though such examination has by no means disproved the presence of ,pleistocene ,man in ,america4 ,dr4 ,a4 ,hrdlika has recently concluded a series of exhaustive studies of the bones of early ,man in both ,north and ,south ,america and of the localities where these bones were found4 ,for both continents he has reached a negative result4 ,as to ,north ,america he says3 8,thus far on this continent no human bones of undisputed geologic antiquity are known40#ag ,for ,south ,america the result is the same4 8,a conscientious1 unbiased study of all the available facts has shown that the whole structure erected in support of the theory of geologically ancient man on that continent rests on very imperfect and incorrectly interpreted data and in many instances on false premises1 and as a consequence of these weaknesses must completely collapse when subjected to searching criticism40 8,the conclusions of the writers with regard to the evidence thus far furnished are that it fails to establish the claim that in ,south ,america there have been brought forth thus far tangible traces of either geologically ancient man himself or any precursor of the human race4 8,this should not be taken as a categorical denial of the existence of early man in ,south ,america1 however improbable such a presence may now appear40#ah ,on the other hand1 the coexistence in ,north ,america of ,man with several extinct species of mammals has been made extremely probable1 if not certain4 ,one of the most striking and best authenticated cases of this was the discovery by ,professor ,williston in western ,kansas of a flint arrowhead beneath and in contact with the skeleton of the extinct ,bison occidentalis4 ,professor ,russell found in lake deposits of ,nevada an obsidian spear-head in association with the bones of an elephant or mastodon1 and other such instances have been reported4 ,in these cases the doubt is as to the geological antiquity of the 8finds10 for the implements are of the type made by the pre-,columbian ,indians4 ,in brief1 there is no convincing evidence that either ,north or ,south ,america was ever inhabited in prehistoric times by races of men different from those first encountered by the ,european discoverers4 ,,chapter ,,xvi ,,history ,,of ,,the ,,edentata ,as here employed1 excluding the so-called edentates of the ,old ,world1 the ,edentata form a highly variegated1 but natural1 assemblage of related forms4 ,the order is at present exclusively ,american and almost confined to the ,neotropical region1 an armadillo which extends into ,texas being the sole exception4 ,these animals are so peculiar and so isolated from other mammals1 that it has been proposed to treat them as a separate subclass2 and there is much to be said in favour of this procedure1 though it would perhaps be premature1 until more is learned concerning these most curious and exceptional animals4 ,in the subjoined table only the more important and better known genera are included4 ,series ,,pilosa4 ,hairy ,edentates ,suborder ,,tardigrada4 ,tree-,sloths ,i4 ,,bradypodid4 ,bradypus1 ,three-toed ,sloth1 ,rec4 ,cholpus1 ,two-toed ,sloth1 ,rec4 ,suborder ,,vermilingua4 ,anteaters ,,ii4 ,,myrmecophagid4 ,myrmecophaga1 ,ant-,bear1 ,rec4 ,tamandua1 ,lesser ,anteater1 do4 ,cyclopes1 ,tree ,anteater1 do4 ,suborder ,,gravigrada4 ,ground-,sloths ,,iii4 ,,megatheriid4 ,megatherium1 ,plio4 and ,pleist41 ,s4 ,a42 ,pleist41 ,n4 ,a4 8,prepotherium1 ,santa ,cruz4 8,planops1 do4 ,,iv4 ,,mylodontid4 ,mylodon1 ,plio4 and ,pleist41 ,s4 ,a42 ,pleist41 ,n4 ,a4 ,paramylodon1 ,pleist41 ,n4 ,a4 ,grypotherium1 ,pleist41 ,s4 ,a4 ,pseudolestodon1 ,plio4 and ,pleist41 ,s4 ,a4 ,scelidotherium1 do4 ,nematherium1 ,santa ,cruz4 ,analcitherium1 do4 ,v4 ,,megalonychid4 ,megalonyx1 ,pleist41 ,n4,a4 ,nothrotherium1 ,pleist41 ,s4 ,a4 ,megalocnus1 ,pleist41 ,cuba4 ,hapalops1 ,santa ,cruz4 ,schismotherium1 do4 ,pelecyodon1 do4 ,megalonychotherium1 do4 ,protobradys1 ,casa ,mayor4 ,series ,,loricata4 ,armoured ,edentates ,suborder ,,dasypoda4 ,armadillos ,,vi4 ,,dasypodid4 ,dasypus1 #f-1 #g- and #h-;,banded ,armadillos1 ,pleist4 and ,rec41 ,s4 ,a4 ,cabassous1 #aa-;,banded ,armadillo1 do4 ,priodontes1 ,giant ,armadillo1 do4 ,tolypeutes1 ,apar1 ,rec41 ,s4 ,a4 ,zadyus1 ,pygmy ,armadillo1 do4 ,scleropleura1 do4 ,chlamydophorus1 ,pichiciago1 do4 ,tatu1 #i-;,banded ,armadillo1 ,pleist4 and ,rec41 ,s4 ,a42 ,rec41 ,texas4 ,eutatus1 ,plio4 and ,pleist41 ,s4 ,a4 ,chlamydotherium1 do4 ,proeutatus1 ,santa ,cruz4 ,prozadius1 ,deseado and ,santa ,cruz1 ,prodasypus1 do4 ,stegotherium1 ,santa ,cruz4 ,meteutatus1 ,deseado4 ,sadypus1 do4 ,amblytatus1 do4 ,pruphractus1 do4 ,,vii4 ,,peltephilid4 ,peltephilus1 ,deseado and ,santa ,cruz4 ,,viii4 ,,incert ,,sedis4 ,metacheiromys1 mid4 ,eoc41 ,n4 ,a4 ,suborder ,,glyptodontia4 ,glyptodonts ,,ix4 ,,glyptodontid4 ,glyptodon1 ,plio4 and ,pleist41 ,n4 and ,s4 ,a4 ,ddicurus1 ,pleist41 ,s4 ,a4 ,panochthus1 do4 ,sclerocalyptus1 ,plio4 and ,pleist41 ,s4 ,a4 ,glyptotherium1 mid4 ,plio41 ,n4 ,a4 ,propalohoplophorus1 ,deseado and ,santa ,cruz4 ,cochlops1 ,santa ,cruz4 ,eucinepeltus1 do4 ,asterostemma1 do4 ,in the section ,pilosa1 which includes the sloths 7,tardigrada71 anteaters 7,vermilingua7 and the extinct ground-sloths 7,gravigrada71 the skin is thickly clothed with long hair1 and in the ,loricata1 armadillos and glyptodonts1 the head1 body1 tail and legs are more or less completely encased in an armour of bony scutes covered with plates of horn1 but with some hairs also4 ,the name ,edentata 7toothless7 is not very happily chosen1 for only the anteaters are quite toothless4 ,almost all the genera have no teeth in the front of the mouth and the teeth are nearly always alike1 so that the distinction of regions among them is entirely a matter of position in the jaws4 ,in the tree-sloths and many ground-sloths the foremost tooth in each jaw is a more or less enlarged1 canine-like tusk4 ,the teeth are always rootless1 growing from permanent pulps1 and are without enamel1 made up of dentine1 which is sometimes homogeneous and sometimes in layers of different hardness1 and with a covering of cement1 usually thin and film-like4 ,the number of teeth varies from #d_/d to #aj_/aj or more1 and their form usually approximates a simple cylinder1 worn off flat at the end1 though the ends may be bevelled or grooved1 differences which are in no way due to pattern but simply to the mode of wear4 ,in the glyptodonts the teeth were divided by deep vertical grooves into two or three pillars1 connected by narrow necks4 ,in most of the edentates there is no change of teeth1 the milk-dentition having been completely suppressed1 but in the #i-;,banded ,armadillo 7,tatu7 each of the permanent teeth is preceded by a two-rooted milk-tooth1 and some other armadillos have milk-teeth4 ,the skull varies much in form and proportions1 according to the character of the food and method of feeding4 ,the tree-sloths and ground-sloths have short1 rounded heads2 in the glyptodonts1 the skull was short and remarkably deep vertically2 while the armadillos have long1 shallow heads1 with tapering muzzle1 the length and slenderness of which differ in the various genera4 ,in the anteaters the skull is extraordinarily elongate and slender4 ,the sagittal crest is seldom present at all and never prominent4 ,the zygomatic arch may be complete or interrupted2 in the tree-sloths1 ground-sloths1 glyptodonts and some extinct armadillos1 there is a descending1 plate-like process given off beneath the eye4 ,the backbone displays some of the most remarkable peculiarities of the order4 ,the neck in the tree-sloths has eight or nine vertebr1 the only instances known among mammals in which the normal number of seven is departed from4 ,in the armadillos and glyptodonts several of the neck-vertebr are cossified into a single piece1 but the atlas is always free1 so as to permit the movements of the head4 ,in the posterior part of the dorsal and in the lumbar region the articulations between the successive vertebr are by far the most complex and intricate known among mammals2 in the tree-sloths these have degenerated1 though still plainly indicated4 ,in the glyptodonts1 which were covered with a huge1 tortoise-like carapace1 mobility of the backbone was needless1 and so all of the dorsal vertebr were united into one long piece and the lumbars were cossified with one another and with the sacrum4 ,the sacrum consists1 throughout the order1 of a very large number of vertebr and is attached to the hip-bones at two different points1 instead of only one1 as in other mammals4 ,the tail varies much in length and thickness2 in the tree-sloths it is extremely short and in the anteaters very long and bushy1 prehensile in the arboreal members of the group2 in the ground-sloths1 especially the gigantic forms1 it was of immense thickness2 while in most of the glyptodonts a varying number of the terminal vertebr were fused together4 ,the sternal ribs are better developed than in any other mammals1 and in the anteaters and ground-sloths they articulate with the breast-bone by regular synovial joints1 and each rib has head and tubercle like a vertebral rib4 ,in the limbs and feet there is great variety1 according to the manner of their employment4 ,the shoulder-blade has a very long acromion and very large coracoid1 which long remains separate from the scapula2 collar-bones are very generally present1 though often in much reduced condition4 ,the hip-bones have in the tree-sloths1 ground-sloths and glyptodonts a much expanded anterior element1 which in the other groups is narrow4 ,the humerus usually has very prominent deltoid and supinator ridges and epicondylar foramen2 the fore-arm bones are always separate1 and there is generally much freedom of rotation of the manus4 ,in the wrist there is no distinct central and usually there are the ordinary eight separate bones4 ,the tibia and fibula are frequently cossified4 ,the tree-sloths1 which lead most strictly arboreal lives and are almost helpless on the ground1 are unique among mammals in that the body is habitually suspended from the limbs1 not carried upon them2 the feet are curved hooks1 which fit over the tree-branches and support the weight without muscular exertion4 ,the limb-bones are very long and slender1 the claws long1 curved and sharp1 and the metapodials of each foot1 two or three in number1 are fused into a single mass4 ,in the ground-sloths there was much change in foot-structure during the course of their recorded development2 they were usually five-toed and the feet were armed with one or more great claws2 the later and larger representatives of the suborder walked upon the outer edge of the feet4 ,the armadillos1 which are largely burrowers1 have five-toed feet and long1 heavy1 pointed claws1 but in some of them the pes has a varying number of flat1 hoof-like nails4 ,the immense glyptodonts had very short1 broad feet1 shod with hoofs1 which1 in some of the genera1 were longer and more claw-like in the manus4 ,the recorded history of the edentates was developed almost entirely in ,south ,america4 ,in the ,casa ,mayor formation there were numerous armadillos1 but as only scutes of the carapace have been found1 little is known of them4 ,the ground-sloths 7,protobradys7 have been reported1 but from such imperfect material that the reference is uncertain4 ,the first assuredly determinable members of this suborder were in the ,astraponotus beds and1 associated with them1 the most ancient known glyptodonts4 ,in the ,deseado stage were many armadillos1 some of them extremely peculiar1 several glyptodonts and ground-sloths1 some species of the latter very large4 ,edentates were far more numerous and varied in the ,santa ,cruz than in any of the preceding stages4 ,tree-sloths and anteaters have both been reported1 but the evidence is insufficient1 though there can be little doubt that these suborders had begun their separate existence in some part of ,south ,america other than ,patagonia4 ,the three families of ground-sloths were already distinguishable1 though much less clearly separated than they afterwards became2 none of them were large animals1 smaller even than some of the ,deseado species and veritable pygmies in comparison with the giants of the ,pliocene and ,pleistocene4 ,the glyptodonts were likewise far smaller than their ,pliocene and ,pleistocene successors and in several respects more primitive1 approximating the armadillos more closely2 nor was there any such variety of forms as in the later stages4 ,the armadillos were extremely numerous and varied2 they all belonged to extinct genera and most of them apparently have no descendants at the present day4 ,the tropical forests of ,brazil and the ,guianas must then1 as now1 have swarmed with mammals which did not extend their range to ,patagonia and of which we consequently have no record4 ,no doubt1 it was in these forests that the ancestors of most modern armadillos1 as well as of the tree-sloths and anteaters1 lived in ,miocene times4 ,pliocene edentates were of the same suborders as those of the ,santa ,cruz1 but far larger in size4 ,most of them are known only from very incomplete specimens1 but the ,pleistocene has yielded an enormous mass of beautifully preserved material4 ,of the tree-sloths and anteaters1 only questionable remains have been found4 ,that these tropical and forest-loving animals should not have occurred in the open ,pampas of ,argentina is not surprising1 but it is difficult to account for their absence from the extremely rich cave-faunas of ,brazil4 ,nearly all the existing genera of armadillos have been obtained1 and with these were associated several extinct genera1 some of them 7,chlamydotherium1 ,eutatus7 relatively huge1 as large as tapirs4 ,there was a wonderful variety of glyptodonts1 most of them enormous creatures1 of which no less than five genera have been collected in ,argentina and ,brazil1 and the ground-sloths were even more numerous and varied4 ,nine genera1 with many species1 of these great beasts1 which ranged in size from an elephant to a tapir1 are already known and no doubt the list is still incomplete4 ,these glyptodonts and ground-sloths must have been among the most conspicuous elements of the ,pleistocene fauna4 ,aside from certain problematical ,eocene forms1 the first ,north ,american edentates1 which were immigrants from the southern continent1 appeared probably in the middle ,miocene of ,oregon in the form of ground-sloths1 but the specimen1 as well as a similar one from the lower ,pliocene of ,nebraska1 is not sufficiently complete for positive reference4 ,in the middle ,pliocene the ground-sloths and glyptodonts were unquestionably present1 and in the ,pleistocene these two suborders were numerously and conspicuously represented4 ,three or four genera of the huge1 elephantine ground-sloths coexisted in ,pleistocene ,north ,america4 ,megalonyx was abundant in the forested regions east of the ,mississippi1 from ,pennsylvania southward1 and on the ,pacific coast2 ,mylodon was transcontinental in distribution2 while ,megatherium was apparently confined to the southern states4 ,while all three genera undoubtedly originated in ,south ,america1 ,megalonyx has not yet been found in that continent4 ,this genus was originally named by ,president ,jefferson in #ahje from an ungual phalanx found in a cave in ,virginia1 and he imagined that it belonged to a colossal lion which must still be living in the mountains of western ,virginia4 ,this was deduced from the assumption that no species could become extinct1 and the passage is of interest as showing the prevalent belief of the time1 although ,cuvier had already demonstrated that many species had actually been extinguished4 ,the passage is as follows3 8,the movements of nature are in a never ending circle4 ,the animal species which has once been put into a train of motion is still probably moving in that train4 ,for1 if one link in nature's chain might be lost1 another and another might be lost1 till this whole system of things should evanish by piecemeal40 ,the glyptodonts were also southern in distribution1 and only very imperfect remains of them have yet been recovered from the ,north ,american ,pleistocene1 quite sufficient1 however1 to make the identification certain4 ,there were several genera of rather small ground-sloths in the ,pleistocene of ,cuba4 ,the best known of these1 ,megalocnus1 had several peculiarities of structure1 but was plainly a member of the ,megalonychid4 ,the ancestors of this genus probably invaded ,cuba in the ,pliocene1 when the island was joined to ,central ,america4 ,,suborder ,,gravigrada4 ,,ground-,,sloths ,as the ground-sloths would appear to have had a more central position within the order than any of the other groups1 our study of development may well begin with them4 ,in the ,pleistocene there were three families of these gigantic brutes1 which ranged through the western hemisphere from ,pennsylvania and ,california to ,patagonia4 ,unfortunately our knowledge of the developmental stages within the different families is very unequal1 and it is therefore impracticable to do more than sketch the changes of the suborder as a whole and in a general way4 ,in the successive geological stages the proportionate representation of the different phyla varied greatly2 in the ,south ,american ,pliocene and ,pleistocene the ,mylodontid and ,megatheriid were the abundant forms1 while the ,megalonychid were but scantily represented4 ,in the ,santa ,cruz ,miocene1 on the other hand1 the overwhelming preponderance was with the ,megalonychid1 the other two families being comparatively rare and incompletely known4 ,from the still more ancient formations1 the material so far collected is so fragmentary that family distinctions have little meaning4 ,after all1 there was no very wide range of variation among the contemporary members of the three families1 and the differences were principally in size1 in the form and number of the teeth1 the shape of the skull and the number of digits2 in essentials they were all much alike4 ,the genus ,megatherium 7,fig4 #abb1 p4 #bbj7 included the largest and most massive members of the suborder1 ,m4 americanum being as large as an elephant1 but very differently proportioned1 as it was much longer and lower in stature1 owing to the shortness of the extraordinarily heavy limbs2 some of the skeletons measure #bj feet or more in length4 ,the teeth1 which were #e_/d in number1 formed an uninterrupted series on each side2 all had the same quadrate form and by abrasion were worn into two transverse ridges1 formed by the meeting of the harder dentine with the thick coating of cement4 ,the result was a form of tooth which much resembled the lower molars of a tapir1 but it was not a tooth-pattern in any proper sense of the word1 being due entirely to the mode of wear4 ,the skull was very small in proportion to the huge body and was low and narrow in shape2 the cranium had a broad1 flat roof1 without sagittal crest2 the orbit was completely encircled in bone1 and the descending process of the zygomatic arch beneath the eye was very long and conspicuous4 ,the nasals were short1 and the slender1 toothless premaxillaries projected far in front of them1 which makes the presence of some sort of a proboscis likely4 ,the lower jaw had a long1 narrow1 spout-like symphysis1 which was abruptly rounded at the free end1 not pointed2 below the teeth1 the lower margin of the jaw was very strongly convex1 descending in a great flange4 ,the neck was short1 the body very long and enormously heavy1 as was also the tail4 ,the immense shoulder-blade had a very long acromion1 which curved forward and inward1 fusing with the coracoid and forming a bony loop or bridge4 ,the hip-bones had the anterior element 7ilium7 enormously expanded transversely1 so as to support the huge mass of viscera in the semi-erect position which the animal1 it is believed1 frequently assumed in feeding4 ,collar-bones were present4 ,the fore limb was very much more slender than the hind1 but of nearly the same length4 ,the humerus had a comparatively slender upper portion and extremely broad lower end1 due to the great development of the internal epicondyle and supinator ridge2 there was no epicondylar foramen4 ,the radius evidently had the power of very free rotation upon the humerus4 ,the femur was short1 flattened antero-posteriorly1 but excessively broad and heavy1 and had no third trochanter4 ,the tibia and fibula were likewise short and very massive and were extensively cossified at each end1 leaving but a short interspace open between the bones4 ,the very peculiar feet were so connected with the limb-bones1 that the animal must have walked upon the outer edge of the foot1 somewhat as the existing ,ant-,bear 7,myrmecophaga jubata7 uses the fore foot4 ,the manus had four functional digits1 the first being a mere vestige2 the fifth1 upon which the weight rested in walking1 had two very small phalanges and no claw1 while the second1 third and fourth had long1 sharp claws4 ,the pes had but three functional digits1 for the first and second were reduced to rudiments2 digit ,,iii had an enormous claw and of this digit the metatarsal was short and very heavy and the first two phalanges were fused together2 the two external digits1 ,nos4 ,,iv and ,v1 had no claws4 ,the astragalus had a very peculiar shape1 made necessary by the application of the external border of the foot to the ground and thus in both fore and hind feet the great claws were turned inward and1 in the case of the pes1 it must have been impossible to rest the sole upon the ground4 ,the heel-bone was enormous and club-shaped and formed the hinder portion of the weight-carrying outer edge of the foot4 ,almost all who have studied the structure of this extraordinary beast are agreed as to its habits4 ,that it fed principally1 if not exclusively1 upon leaves1 is indicated by the teeth4 ,the general opinion as to its manner of life is well summed up by von ,zittel3 8,the hip-bones1 hind legs and tail are characterized by enormous strength4 ,the entire structure of the extremities proves that the gigantic sloth could move over the ground but slowly and clumsily2 on the other hand1 the fore limbs served as grasping organs and were presumably employed to bend down and break off twigs and branches and even to uproot whole trees1 while the weight of the body was supported upon the hind legs and tail40#ai ,it would be quite absurd to suppose that such ponderous animals could have been climbers or burrowers1 hence the function of the enormous claws1 especially the single one of the pes1 is not obvious1 though they may have been merely the weapons of the otherwise defenceless monsters4 ,the great claw in the fore foot of the ,ant-,bear is a terrible weapon1 with which the creature vigorously and successfully defends itself against dogs1 and it may even be dangerous to men1 if incautiously molested4 ,megatherium had no bony scutes1 or other ossifications in the skin1 so far as is known1 and was probably covered with long and coarse hair1 as is known to have been the case in another ground-sloth4 ,less specialized in many respects than the megatheres was ,mylodon1 type of a family which was numerously and variously represented in the ,pleistocene of ,south ,america1 much less so in that of ,north ,america4 ,mylodon was smaller and lighter1 being from to smaller in linear dimensions than ,megatherium1 and the contemporary ,scelidotherium was no bigger than a tapir4 ,the teeth numbered #e_/d and the anterior one above and below had a somewhat tusk-like form2 the others were worn off evenly1 with nearly horizontal grinding surface1 but a vertical groove on the inner side gave them a subtriangular1 lobate form4 ,the skull was short and broad1 with flat top1 and orbit only partially enclosed behind2 the premaxillaries were very short and the muzzle very broad and abruptly truncated1 the nasal opening very large4 ,the lower jaw had a straight inferior border1 a short1 very wide and shovel-shaped symphysis and square chin4 ,nothing indicates a proboscis1 and the head must have been very different from that of ,megatherium4 ,within the family of the mylodonts there was some variety in the dentition and more in the shape of the skull4 ,in ,lestodon1 for example1 the first tooth in each jaw was a large1 sharp-pointed tusk1 the muzzle was greatly broadened1 and the whole animal was larger4 ,scelidotherium1 the smallest ,pleistocene member of the family1 had a much narrower and more elongate skull than the others4 ,in ,glossotherium1 which also had an elongate skull1 there was an arched bony bridge connecting the anterior end of the nasal bones with the premaxillaries and dividing the nasal opening into two parts4 ,the neck1 body and tail of ,mylodon did not differ materially from those of ,megatherium1 except in being smaller and less massive4 ,the fore limb was relatively somewhat shorter and much stouter1 but otherwise similar2 the humerus had no epicondylar foramen and the femur no third trochanter2 the tibia and fibula were separate4 ,the manus had five digits1 ,nos4 ,i1 ,,ii and ,,iii carrying claws1 that of ,,iii being especially large2 ,,iv and ,v had no claws and the outer edge of the manus rested on the ground in walking1 the sole turned inward4 ,the pes had lost the first digit1 the second and third had claws1 but not the fourth and fifth2 the weight rested on the outer edge4 ,the skin is definitely known from large pieces belonging to the allied genus ,grypotherium1 found in a cavern near ,last ,hope ,inlet1 ,patagonia1 where it had been preserved by burial in dry dust4 ,externally1 the skin was thickly covered with coarse hair and in the deeper layers was a continuous armour of small ossicles1 which were close set and in the ,last ,hope specimens show like a cobble-stone pavement on the inner side of the skin1 the innermost layers of which have been destroyed2 in life1 these small bones were not visible4 ,similar ossicles have been found in association with several skeletons of ,mylodon4 ,the habits1 diet and mode of feeding of the latter were no doubt essentially similar to those of ,megatherium1 but ,scelidotherium1 which had a much shorter and lighter tail1 was probably more quadrupedal and browsed upon low shrubbery4 ,illustration3 ,,fig4 #bhh4--;,gigantic ground-sloth 7,mylodon robustus71 ,pampean4 ,restored from ,owen's figure of the skeleton4 ,the third family1 the ,megalonychid1 was scantily represented in the ,pleistocene of ,south ,america1 but relatively common in ,north ,america4 ,megalonyx was1 on the whole1 less specialized than ,mylodon or ,megatherium1 but had a strong resemblance to both of them4 ,the teeth1 #e_/d in number1 had the foremost one in each jaw separated by a considerable space from the others and more or less tusk-like in form2 the grinding teeth were worn smooth1 without ridges1 and of somewhat trihedral shape4 ,the skull was short1 broad and deep1 resembling in shape that of the tree-sloths2 there was a long1 but feebly developed sagittal crest1 and the orbits were widely open behind1 with hardly a trace of any posterior boundary4 ,the muzzle was very short and broad and abruptly truncated and the premaxillary bones were extremely small4 ,the lower jaw was short1 thick and massive1 with very broad symphysis and almost vertical chin4 ,neck1 body1 tail1 shoulder and hip-bones did not differ sufficiently from those of ,megatherium to require particular notice4 ,the fore limb was shorter and more slender than the hind2 the humerus had the epicondylar foramen and the very massive femur retained the third trochanter2 the tibia and fibula were separate4 ,the feet had five digits1 three of which carried claws2 the calcaneum was very peculiar1 not at all like the massive1 club-shaped bone of ,megatherium and ,mylodon1 but long1 comparatively thin and sickle-shaped4 ,nothing in the skeleton suggests that the creature's habits differed in any important way from those of the genera last named4 ,megalocnus1 of the ,cuban ,pleistocene1 a member of this family1 was apparently peculiar to the island and was probably derived from ancestors which in the ,pliocene migrated from ,central ,america4 ,aside from certain remarkable peculiarities of the teeth1 this animal was more primitive1 as well as smaller1 than any other of the ,pleistocene genera4 ,although remains of ,gravigrada are comparatively common in all of the fossiliferous formations between the ,pampean and the ,santa ,cruz1 the material is too imperfect to throw any useful light upon the development of the various families4 ,from the ,santa ,cruz beds1 on the other hand1 a great wealth of specimens has been obtained1 and it is possible to give some fairly adequate account of the ground-sloths of that time4 ,these animals were then extremely abundant individually and of extraordinary variety2 evidently1 they were in a state of rapid expansion and divergent evolution along many lines1 for hardly any two specimens are alike and therefore the satisfactory discrimination of species is well-nigh impossible4 ,yet1 with all this remarkable variability1 the range of structural differences was not great2 the group was a very homogeneous and natural one1 and separation into families was not obvious4 ,two of the three families were1 however1 unequivocally present in this fauna and the third somewhat doubtfully so4 ,the ,megalonychid1 which in the ,south ,american ,pleistocene had dwindled to such insignificant proportions1 formed the overwhelming majority of the ,santa ,cruz ,gravigrada2 the ,mylodontid were quite rare in comparison and are still very incompletely known2 while the ,megatheriid1 though probably present1 have not been identified beyond all doubt4 ,all of the ,santa ,cruz ground-sloths were small animals1 the largest not approximating the smallest ,pleistocene species1 those of ,cuba excepted1 and many of them were no larger than the modern tree-sloths4 ,this was a wonderful difference between the ,santa ,cruz and the ,pampean1 but a difference which involved nearly all other groups of mammals4 ,so far as the skeleton is concerned1 this is known with completeness only for the ,megalonychid1 especially the genus ,hapalops2 but enough has been learned of the others to show that there was far less difference between the families than had arisen in the later epochs4 ,this backward convergence of the three groups towards a common term plainly indicates their common origin1 being exactly what might have been predicted in advance of experience4 ,illustration3 ,,fig4 #bhi4--,santa ,cruz ground-sloth 7,hapalops longiceps7 and glyptodont 7,propalohoplophorus australis74 ,restored by ,knight from skeletons in ,princeton ,university and the museum of ,la ,plata4 ,in all the genera the teeth number #e_/d2 the teeth on each side were sometimes in continuous series1 sometimes the first one was isolated and almost always more or less tusk-like1 most so in ,eucholops4 ,the other teeth were usually of transversely elliptical shape and worn into two ridges1 with a hollow between2 the mylodonts 7,nematherium1 etc47 already had the triangular1 or lozenge-shaped1 lobate form of teeth1 characteristic of the family4 ,the skull varied considerably in its proportions2 generally1 it was long and narrow1 with shortened face and elongate cranium2 the sagittal crest was seldom present1 never prominent1 and the orbit was always widely open behind1 without postorbital processes4 ,the premaxillaries were always short and toothless and in most of the genera they were slender rods1 in others 7e4g4 ,hyperleptus7 broad and plate-like4 ,the lower jaw had an elongate spout-like symphysis1 in which the two halves were cossified1 tapering forward to a blunt point and1 though the length of this spout differed greatly in the various genera1 in none was there a broad1 abrupt chin such as ,mylodon and ,megalonyx had4 ,in ,prepotherium1 which is believed to be referable to the ,megatheriid1 the lower jaw had the extremely convex inferior border1 in less exaggerated degree1 of its huge ,pampean successor2 it would be premature to say descendant4 ,while the long1 slender skull was the prevailing type among the ,santa ,cruz ,gravigrada1 there was a group of small animals in which the skull was shorter and more rounded and had a very suggestive likeness to that of the modern tree-sloths1 as was likewise true of the teeth4 ,despite innumerable variations of detail1 the skeleton of the ,santa ,cruz ground-sloths may be described without distinction of genera1 though it should be added that the skeleton is but partially known in many of the genera1 and fuller knowledge might require modification of some of the statements4 ,the neck was of moderate length1 the body long1 the tail long and heavy and1 in some instances1 very massive4 ,the sternal ribs were completely ossified and already had the same elaborate mode of articulation with the breast-bone as in the great ,pampean forms1 and the vertebr the same intricate connections4 ,the shoulder-blade also had the same characteristics as in the latter1 but the hip-bones had but a moderate transverse expansion1 having no huge mass of viscera to support4 ,the limbs were stout and short1 fore and hind legs of nearly equal length2 the humerus had the epicondylar foramen and the broad1 flattened femur retained the third trochanter4 ,the radius had a discoidal upper end1 which rotated freely upon the humerus2 the tibia and fibula were always separate4 ,the feet were five-toed1 all the digits complete and functional and all provided with claws2 there was no cossification between the phalanges4 ,the astragalus was little different from the normal form1 but in some genera 7e4g4 ,prepotherium7 the highly peculiar form of this bone characteristic of ,mylodon and ,megatherium was distantly foreshadowed4 ,the gait must have been simply plantigrade1 though some of the forms had probably begun to throw the weight upon the outer edge of the foot4 ,illustration3 ,,fig4 #bij4--,left pes of ,mylodon1 ,pampean 7after ,owen74 ,cal41 calcaneum4 ,as41 astragalus4 ,n41 navicular4 ,cn4 #b1 ,cn4 #c1 middle and external cuneiforms4 ,cb41 cuboid4 ,no dermal armour has yet been found in association with any of the genera1 and1 so far as the predominant ,megalonychid are concerned1 of which so many skeletons have been collected1 this negative evidence must be allowed great weight4 ,but the material of the other two families is so rare and incomplete1 that the failure to find dermal ossicles is of no value in determining the question2 probably1 the mylodonts possessed them4 ,these small ,santa ,cruz ground-sloths were not so clumsy and slow-moving as their gigantic successors of the ,pampean1 and must have been inoffensive plant-eaters1 some of them perhaps more or less arboreal in habits1 but they could defend themselves with their long1 sharp claws4 ,illustration3 ,,fig4 #bia4--,left pes of ,hapalops1 ,santa ,cruz4 ,princeton ,university ,museum4 ,letters as in ,fig4 #bij and scale of reduction the same4 ,it would require far too much space and lead us into a labyrinth of anatomical technicalities to point out all the many resemblances to other edentate suborders which are to be noted in the skeleton of the ,santa ,cruz ,gravigrada1 which thus justified their position as the most nearly central group of the entire order4 ,not only was the skeleton of these ,miocene ground-sloths very much less specialized than in their ,pleistocene successors1 but they were much closer to the anteaters than were the latter4 ,aside from the skull1 all parts of the skeleton displayed this resemblance in so marked a manner that the common derivation of the two suborders seems hardly open to question4 ,different as was the skull in the two groups1 the differences were not such as to preclude the origin of both from the same type4 ,even more closely connected were the ground-sloths and the tree-sloths2 the resemblance was most clear in the teeth and skull1 but there were also many points of likeness throughout the skeleton4 ,in the tree-sloths the entire bony structure has been profoundly modified in adaptation to their altogether exceptional mode of life1 in hanging suspended from the branches of trees2 but1 despite this modification1 there are so many notable resemblances between the ,santa ,cruz ,gravigrada and the existing ,tardigrada as irresistibly to suggest their community of origin1 and thus the former served to connect the anteaters1 on the one hand1 with the tree-sloths1 on the other4 ,this must not be construed as meaning that the ,miocene ground-sloths were the ancestors of the other suborders1 which were probably already in existence as distinct groups1 but merely that all three suborders had a common origin1 from which the ,santa ,cruz ,gravigrada had departed less than have the sloths and anteaters4 ,there is evidence that at least two of the ground-sloth families1 the ,megalonychid and the ,mylodontid1 were distinguishable in the ,deseado stage1 but materials are still lacking to give us any real knowledge of the suborder in that or the more ancient stages4 ,,section ,,loricata4 ,,armoured ,,edentates ,,suborder ,,dasypoda4 ,,armadillos ,armadillos are still an important and characteristic element of the ,neotropical fauna1 ranging from ,texas to ,patagonia and showing a considerable variety of structure and appearance4 ,existing species are all of small or moderate size1 and the one which is by far the largest 7,priodontes gigas7 may somewhat exceed three feet in length1 exclusive of the tail1 and the smallest 7,chlamydophorus truncatus7 is hardly more than five inches long4 ,in most armadillos the hair is greatly diminished in quantity and the animal is sheathed in a conspicuous armour of bony scutes1 covered with horny plates4 ,there is a head-shield which covers the top of the skull1 and the tail is enclosed in a sheath2 the back and sides are protected by the great carapace and the limbs by irregular scutes and scales1 leaving only the under side of the body and the inside of the legs uncovered4 ,in most existing genera1 the carapace is in three parts1 an anterior and posterior buckler1 in which the plates are immovably fixed together by their edges1 and between a varying number of transverse1 overlapping bands1 from #c to #ac1 which permit sufficient flexibility of the body4 ,the tail-sheath is made up of a series of rings4 ,one genus 7,tolypeutes7 has the power of rolling itself into a ball1 the head-shield exactly closing the anterior notch of the carapace and the tail-sheath filling the posterior notch4 ,the animal is thus perfectly protected against attack and does not seek refuge by digging1 as other armadillos do and with astonishing rapidity4 ,in the little ,pichiciago 7,chlamydophorus7 the dermal ossifications are very thin and the carapace is composed of twenty transverse bands of horny plates1 without bucklers2 the rump is covered with a broad and heavy shield of bone1 overlaid with thin plates of horn1 which is attached to the hip-bones and notched below for the short tail4 ,in certain rare and little known genera there is a greater development of hair2 in one 7,praopus7 the whole carapace is covered with a dense coat of hair1 and in another 7,scleropleura7 the middle of the back has only a hairy skin and the carapace is restricted to the sides4 ,the teeth vary in number and size in the different genera2 in some 7e4g4 ,dasypus7 there is one upper incisor on each side2 the teeth are all simple and of nearly cylindrical form4 ,the skull is low and flattened1 with long tapering snout and orbits widely open behind2 the zygomatic arches are uninterrupted4 ,most of the vertebr of the neck are fused into a single piece2 in the lumbar and posterior dorsal regions there are not only the usual highly intricate articulations between the vertebr1 but also high processes on each side for the support of the carapace4 ,the fully ossified sternal ribs have movable joints with the breast-bone1 but not the double articulations found in the anteaters and ground-sloths4 ,the shoulder-blade has a very long acromion1 which does not form a bony loop with the coracoid1 and the clavicles are complete4 ,the anterior element 7ilium7 of the hip-bone is narrow1 very different from the broad plate of the ,gravigrada4 ,the humerus has prominent deltoid and supinator ridges and an epicondylar foramen1 and the femur has the third trochanter4 ,though the fore-arm bones are separate1 the radius has no freedom of rotation2 tibia and fibula are cossified at both ends4 ,in the hind foot there is no great variety of character2 it is five-toed and usually has claws1 but may have broad1 flat nails 7e4g4 ,priodontes71 but the manus1 which is a burrowing organ1 displays different degrees of specialization1 which is carried farthest in the ,giant ,armadillo 7,priodontes74 ,tatu has the fore foot of quite different type4 ,the armadillos feed chiefly upon insects and worms1 but they are omnivorous and eat roots and carrion and sometimes even capture and devour small rodents and lizards4 ,as in the case of the ground-sloths1 the fossil armadillos so far available are insufficient for tracing the history of the various phyla1 or for doing more than making a very brief sketch of the development of the suborder as a whole4 ,nearly all of the modern genera have been found in the ,pleistocene together with several that are extinct1 some of the latter of very large size4 ,one of these1 ,eutatus1 had a carapace without bucklers and made up of #cc movable1 transverse bands4 ,another1 ,chlamydotherium1 as large as a rhinoceros and the largest known armadillo1 had anterior and posterior bucklers1 with several movable bands between2 it was especially characterized by the teeth1 which were divided by a vertical groove into pillars or lobes1 thus approximating the teeth of the glyptodonts4 ,the genus went far back into the ,pliocene1 and the more ancient species were successively smaller4 ,though remains of armadillos abound in the formations between the ,pampean and the ,santa ,cruz1 they are for the most part so fragmentary as to be of no service in deciphering the history of the group4 ,in the ,santa ,cruz beds also they are very abundant and varied1 and several of the genera are very completely known4 ,as a whole1 this assemblage of armadillos was very different from that of the ,pleistocene1 and only a few direct ancestors of the latter have been found in the ,miocene of ,patagonia2 no doubt1 like the ancestral tree-sloths and anteaters1 they were then living in the warmer regions of the north4 ,most of the ,santa ,cruz armadillos belonged to aberrant types1 of which no descendants have survived2 but1 nevertheless1 they throw welcome light upon the developmental stages of the suborder4 ,illustration3 ,,fig4 #bib4--,skull of ,peltephilus1 ,santa ,cruz4 ,ameghino collection4 ,these armadillos had the complete armour of head-shield1 carapace and tail-sheath1 but the carapace had no anterior buckler in any of the ,santa ,cruz genera1 and in some there was no posterior buckler1 the carapace consisting entirely of transverse1 movable bands1 as in the ,pleistocene ,eutatus4 ,in one especially peculiar genus1 ,peltephilus1 the head-shield was remarkable2 it was made up of large1 polygonal plates1 the two anterior pairs of which were elevated into high1 sharp points1 which must have supported horns1 that were quite large in proportion to the size of the animal4 ,a #d-;horned armadillo1 like a tiny rhinoceros in armour1 must have been a sufficiently bizarre object4 ,as a rule1 the teeth of the ,santa ,cruz armadillos were of the same simple1 cylindrical form as in the modern genera and arranged in the same way1 but there were some exceptions4 ,in the horned ,peltephilus1 the teeth of each jaw were so inserted as to form a continuous series around the sides and front of the mouth2 and1 at first sight1 it would seem that this genus differed from all other known edentates in having a full set of incisors1 but actually it had but one on each side above and below1 as has the modern ,dasypus1 with the difference that1 in the latter1 the incisors of the opposite sides are widely separated and in ,peltephilus were brought close together4 ,the anterior upper teeth were long and sharp and passed outside of the lower ones1 when the jaws were closed1 and all the teeth had an external layer of hard and shining dentine1 which had almost the appearance of enamel4 ,another variant in dentition was ,proeutatus1 which was the largest of ,santa ,cruz armadillos and larger than any existing forms except ,priodontes and ,cabassous4 ,it had teeth like those of the huge ,pliocene and ,pleistocene ,chlamydotherium1 of which it was a probable ancestor2 the five posterior ones in each jaw were of trihedral shape1 and the two kinds of dentine1 of which they were composed1 were so arranged as to form a rough grinding surface4 ,probably this animal subsisted largely upon vegetable food2 at all events1 the food was of such a nature as to keep the teeth worn down more than in any of the associated genera4 ,a fourth type of dentition was displayed by ,stegotherium 7,fig4 #bdc1 p4 #dhj72 the teeth were so few and small that they can have had no functional value and were merely minute points almost level with the gums4 ,in all probability1 ,stegotherium was more exclusively insectivorous than the other genera4 ,among the ,santa ,cruz armadillos may be distinguished four well-marked types of skull4 7#a7 ,that which agrees closely with the modern form1 especially as exemplified by the genus ,dasypus4 7#b7 ,proeutatus had a higher and less flattened cranium and a very long1 cylindrical muzzle4 7#c7 ,in the horned ,peltephilus the face was very short and broad1 and the lower jaw was horseshoe-shaped1 the two halves cossified at the symphysis1 which is not true of any other armadillo4 7#d7 ,quite the opposite extreme was displayed by ,stegotherium1 in which the face was drawn out into a very long1 slender and tapering muzzle2 the lower jaw was extremely weak and thin1 the posterior1 ascending portion low and ill-defined1 the condyle and coronoid process much reduced4 ,no other known armadillo has such fragile jaws1 and there was a distinct likeness in the skull to that of the ,ant-,bear4 ,illustration3 ,,fig4 #bic4--,skull of ,proeutatus1 ,santa ,cruz4 ,princeton ,university ,museum4 ,illustration3 ,,fig4 #bid4--,skull of ,stegotherium1 ,santa ,cruz4 ,princeton ,university ,museum4 ,aside from carapace and skull1 the skeleton of the ,santa ,cruz armadillos was surprisingly modern4 ,the vertebr of the neck were cossified1 those of the lumbar and posterior dorsal regions had the extremely complex articulations and the high processes for the support of the carapace1 just as in the ,recent genera4 ,the limb-bones did not differ in any significant way from those of the latter1 and the feet closely resembled those of the modern ,dasypus2 none of the genera displayed the specialization of the manus seen in ,cabassous1 ,priodontes or ,tolypeutes4 ,whether these specializations have all been acquired since ,santa ,cruz times1 or whether they had already appeared in some other region of the continent1 is a question that remains to be determined4 ,little can yet be done in the way of tracing the history of the armadillos through the stages preceding the ,santa ,cruz times1 because of the fragmentary character of the material4 ,the suborder was abundantly represented in the ,deseado stage1 in which some of the ,santa ,cruz genera existed4 ,even in the most ancient of the ,patagonian ,tertiary formations are found scutes of the carapace essentially like those of the modern armadillos4 ,the group is thus of very high antiquity1 older than any other of the suborders is known to be4 ,in addition to the typical armadillos of ,south ,america1 there were1 in other continents1 certain more or less doubtful forms1 concerning which a word should be said4 ,in the ,bridger ,eocene of ,north ,america was a genus 7,metacheiromys7 of armadillo-like animals1 the true relationships of which are far from clear4 ,the teeth were mostly lost1 leaving but one on each side of each jaw1 and this was covered with enamel1 which is not true of any unquestioned edentate4 ,however1 this is not an insuperable objection to the inclusion of these animals in the edentates1 for there can be no doubt that these were derived from ancestors with enamel-covered teeth4 ,even in modern armadillos the enamel-organ is formed in the embryo1 though it does not perform its functions4 ,the skull of ,metacheiromys had something of the armadillo-shape1 but was not especially characteristic4 ,the vertebr of the neck were all separate1 and those of the dorsal and lumbar regions did not have the complex articulations common to all known edentates1 fossil and ,recent2 the sacrum had on each side but one point of contact with the hip-bones1 and the sternal ribs were not ossified4 ,the shoulder-blade1 hip-bones and humerus were all armadillo-like4 ,the plantigrade feet were five-toed and the metapodials were very edentate in form4 ,no indication of bony armour has been found4 ,while these curious animals may very possibly have been referable to the ,edentata and1 at all events1 had several features suggestive of relationship to that order1 it can hardly be maintained that they were unequivocal members of it4 ,in the ,oligocene of ,france have been obtained some very fragmentary fossils which were classified and described as armadillos1 but their character is quite problematical4 ,it is thus possible1 though far from certain1 that in the early ,tertiary1 armadillo-like edentates were spread all over the northern hemisphere4 ,,suborder ,,glyptodontia4 ,,glyptodonts ,in the ,pliocene and ,pleistocene these huge armoured creatures ranged from the southern ,united ,states to ,patagonia4 ,that they were nearly related to the armadillos is clear1 but they were so greatly modified and specialized as to demand recognition as a distinct suborder4 ,aside from their enormous size1 the most striking feature of the ,glyptodontia is the extraordinary development of their defensive armour1 which was far more complete and massive than in the armadillos4 ,the top of the head was protected by a thick head-shield1 or casque1 composed of several cossified plates2 the body and much of the limbs were enclosed in the immense carapace of elongate-oval1 domed shape1 which covered the neck and trunk and on the sides almost reached to the ground4 ,this tortoise-like carapace was composed of very thick1 polygonal plates of bone 7no doubt covered externally with horny plates7 immovably fixed together by their rough edges1 and ornamented with an elaborate pattern of sculpture1 which varied according to the genus4 ,with one or two exceptions1 the plates of the carapace were not arranged in transverse rows1 but formed a mosaic without discernible banding4 ,in the exceptions noted1 the sides of the carapace were made up of bands1 and near the margins were two or three overlapping transverse bands which permitted a minimal degree of flexibility4 ,the tail-sheath was remarkable and differed much in appearance and make-up in the various genera4 ,in ,glyptodon the tail was comparatively short and the tail-sheath was made up of a series of overlapping rings1 each ring consisting of two rows of plates2 those of the second row were ornamented1 on the top and sides of the tail1 with very prominent1 conical projections1 capped1 in the living animal1 with still longer and sharper spines of horn1 so that the tail must have bristled with spikes4 ,a more usual type of tail-sheath was exemplified by ,sclerocalyptus1 in which there were several overlapping rings at the root of the tail1 but for much the greater part of its length the plates of the sheath were fused together into a long1 transversely oval tube1 tapering very gently to the free end1 where it was bluntly rounded4 ,a modification of this type was the very long tail-sheath of ,panochthus1 in which there were seven overlapping rings at the root1 followed by a long1 massive tube1 the sides of which were set with three or more large and heavy1 horn-like spines4 ,in ,ddicurus was reached the maximum specialization of this type2 the very long tube had its free end greatly expanded and thickened into a huge1 club-shaped mass1 on the top and sides of which were fixed long and sharp horns4 ,the teeth1 which in all the known genera numbered #h_/h1 were all very much alike2 each was divided by two broad and deep vertical grooves on each side into three pillars1 connected by narrow necks4 ,harder dentine in the centre and on the periphery of the tooth1 with a softer intermediate layer1 kept the grinding surface rough through differential wear4 ,teeth of this character are indicative of a vegetable diet and these great creatures were1 no doubt1 as harmless and inoffensive as possible4 ,illustration3 ,,fig4 #bie4--,pampean glyptodonts1 ,ddicurus clavicaudatus and ,glyptodon clavipes4 ,restored from skeletons in the museums of ,la ,plata and ,buenos ,aires4 ,the skull was remarkably short1 broad and high1 the facial region being especially abbreviated2 the cranium1 though forming the greater part of the skull1 was yet small in comparison with the size of the animal2 it had a distinct1 though not prominent1 sagittal crest4 ,the occipital surface was inclined forward and had a very elevated position1 the condyles being near the top of the head and raised very far above the level of the teeth4 ,the orbits were relatively small1 more or less completely encircled with bone and as near to the top of the head as they could be brought2 this was to make room for the extremely high teeth1 which required a great depth of jaw2 the elevation of the whole cranium left unlimited space for the jaws beneath it4 ,the zygomatic arches were strong and curved out widely from the sides of the skull2 beneath each eye was given off a very long descending process which projected downward1 outside of the lower jaw4 ,in most of the species the upper profile of the skull was nearly straight1 but in ,panochthus it descended very steeply from the forehead to the nose4 ,the forehead was dome-like and the nasals extremely short4 ,sinuses were extensively developed1 especially in the frontals1 and in ,sclerocalyptus the bones around the nostrils were grotesquely inflated4 ,the two halves of the lower jaw were fused together1 and the symphysis was prolonged into a short1 wide spout1 which projected considerably in advance of the upper jaw1 showing that the soft parts of the muzzle must have had a corresponding extension4 ,the horizontal portion of the lower jaw1 carrying the teeth1 was short and very deep2 the posterior1 ascending portion had a forward inclination and was very high4 ,the skeleton of the ,pleistocene glyptodonts was unique among mammals1 though evidently a modification of the armadillo type4 ,the extreme modification was conditioned by the enormous weight of the carapace1 which the skeleton had to support4 ,the neck was very short1 made up of short vertebr1 which were extensively cossified2 the atlas was always free1 but the axis was fused with a varying number of the succeeding vertebr2 usually1 the axis and the third to the sixth formed one mass1 while the seventh was fused with the dorsals4 ,the joint between the sixth and seventh vertebr was such as to permit at least a partial downward bending of the head beneath the carapace1 closing its anterior opening with the head-shield4 ,the seventh neck vertebra and all the dorsals1 except the last one1 were cossified into a heavy curved rod1 the 8dorsal tube02 the conjoined neural arches formed a tunnel for the spinal cord and the spines made a continuous ridge4 ,as the hind legs were very much longer than the fore1 the back was strongly arched upward from the neck to the hips4 ,the last dorsal1 the lumbars and the sacrum were all fused together to form the 8lumbo-sacral tube10 of which the cossified neural spines made a very prominent ridge1 the principal support of the carapace in the median line2 the anterior half of the trunk skeleton1 comprising the short1 deep thorax1 was free from the carapace1 which in that region must have rested upon the muscles of the back and shoulders4 ,the number of neck and trunk vertebr combined varied in the different genera from #bf to #bh1 but fusion had reduced the number of separate parts to #d1 or at most #e4 ,such greatly diminished flexibility of the back was rather an advantage4 ,the tail differed much in length in the various genera1 but was always massive2 the anterior vertebr1 usually #g in number1 were free1 the others were fused into a heavy1 tapering rod2 but for nearly its whole length the processes of the vertebr were very prominent1 each vertebra touching the tail-sheath at five points and thus giving it very effective support4 ,in ,glyptodon the tail-vertebr were all free4 ,in most of the genera the scapula was very broad and had the very long acromion common to all the edentates2 there were no clavicles4 ,the hip-bones were very peculiar2 the anterior element 7ilium7 stood almost vertically1 at right angles to the backbone1 and formed a broad plate1 facing forward1 the top of which was roughened and thickened to support the carapace4 ,the posterior element 7ischium7 was also much expanded1 but faced outward1 and its hinder end1 curved upward and thickened1 was another point of strong support for the carapace4 ,the two elements together formed an inverted arch1 the crown of which rested on the head of the femur4 ,though less massive than those of the hind leg1 the bones of the fore limb were yet very heavy4 ,the humerus was short and had reduced deltoid and supinator ridges and no epicondylar foramen2 the short fore-arm bones were separate and heavy1 the ulna especially so4 ,the femur was much the longest of the limb-bones and was extremely strong1 especially in its great breadth1 the antero-posterior flattening1 common to nearly all very heavy mammals1 being well marked4 ,a very unusual feature was the position of the third trochanter near the lower end of the shaft4 ,the tibia and fibula were much shorter than the femur1 extremely heavy and cossified at both ends4 ,the very short and broad feet retained five digits2 in the manus the claws were sometimes comparatively long and sharp1 sometimes blunt and hoof-like2 those of the hind foot were always broad hoofs4 ,among all the many strange and grotesque mammals which the study of fossils has brought to light1 none can have been more remarkable than the ,pleistocene glyptodonts2 slow-moving hillocks they must have seemed1 the larger species #ab to #ad feet long and #e feet or more in height4 ,those that had claws on the fore feet probably used them to dig for roots and tubers1 but all were plant-feeders4 ,when attacked by the sabre-tooth tigers 7,smilodon7 or the great bears 7,arctotherium7 they needed only to squat down1 bringing the edges of the carapace to the ground1 and draw in the head1 to be perfectly protected1 while a sweep of the spiny or club-like and horned tail would have been fatal to anything in its path4 ,as in the case of so many other groups1 little has yet been learned regarding the history of the glyptodonts during the interval between the later ,pliocene and the ,santa ,cruz2 the intermediate formations have yielded many glyptodonts1 but not in such preservation as to be of any service in this connection4 ,we find1 as might be expected1 many and very great differences between the ,pampean and the ,santa ,cruz representatives of the suborder1 the latter being in all respects less modified and less widely removed from the armadillos4 7#a7 ,the most obvious and striking distinction was in size1 the ,santa ,cruz forms being all small and some of them very small4 7#b7 ,in all cases the carapace was made up of transverse bands1 which permitted a slight degree of flexibility1 and near the anterior end1 at the margins of the shell1 were two or three overlapping bands4 ,the plates were thin and were but rarely cossified2 the ornamentation was made by shallow grooves4 7#c7 ,the tail-sheath1 which was of very uniform character1 consisted of two quite distinct portions2 the anterior region consisted of #e or more freely movable1 overlapping rings1 each of two rows of plates1 and in the posterior region the rings were closely fitted together1 less distinctly marked and not movable4 ,this posterior portion was sometimes thick and ended abruptly1 sometimes slender and tapering and in one genus 7,asterostemma7 it was very armadillo-like4 ,in none of the genera were there any spines or horns1 nor were the separate plates ever fused together to form a tube4 7#d7 ,there was considerable variety in the head-shield1 which was usually made up of many separate plates1 but in one genus 7,eucinepeltus7 they were cossified into a single heavy casque4 7#e7 ,the teeth had a less extreme height and the four anterior ones of each jaw were much simpler than in the ,pampean forms4 ,an interesting survival was the retention of two minute incisors in each premaxillary bone1 in one genus 7,propalohoplophorus71 but these were of no functional value and were early lost4 7#f7 ,the skull was much longer1 narrower and lower and had a relatively longer facial portion2 the occiput was higher and more erect1 and the condyles had no such elevation above the level of the teeth2 the orbit was widely open behind and the descending process given off from the zygomatic arch beneath the eye had no such exaggerated length2 the bones were not conspicuously inflated by sinuses4 ,the lower jaw was shallower1 the symphysis and anterior spout shorter and the ascending portion far lower4 7#g7 ,the backbone had a greater number of separate parts2 the atlas1 as always1 was free1 the axis was fused with two or three of the following vertebr2 the sixth was free and the seventh fused with the first and second dorsals to form one piece1 which was succeeded by two or three separate vertebr3 the other dorsals1 except the last one1 were united in the dorsal tube1 and the lumbo-sacral tube was already complete4 ,thus1 instead of four or five1 there were eight or nine distinct parts4 ,none of the tail-vertebr were fused together4 7#h7 ,there was the same disparity in the length of the fore and hind limbs1 but the bones were far more slender and armadillo-like2 this was especially true of the radius and humerus1 the latter having well-developed deltoid and supinator ridges and epicondylar foramen2 the ulna was more massive and glyptodont-like4 ,the femur was very much more slender and rounded and the third trochanter was placed higher up the shaft2 tibia and fibula were cossified at both ends and resembled those of the ,pampean genera1 except for their much greater slenderness4 7#i7 ,the feet were much as in the latter1 but relatively narrower1 and the manus had longer claws4 ,in short1 the ,santa ,cruz glyptodonts departed much less widely from the armadillos than did the ,pliocene and ,pleistocene genera1 and1 to a certain extent1 bridged over the gap between the two suborders4 ,such backward convergence in time is very strong evidence for the community of origin of the two groups4 ,the glyptodonts of the more ancient formations1 so far as they are known1 teach us little concerning the stages of modification in these extraordinary animals1 because of their fragmentary condition4 ,the oldest stage in which representatives of the suborder have been detected is the ,astraponotus beds1 which may be ,oligocene or upper ,eocene4 ,on the face of the records1 therefore1 the glyptodonts had no such antiquity as the armadillos4 99 99 99 99 99 ,it has long been recognized that the ,edentata occupy a very isolated position among the placental mammals2 their relationships to other orders and their point of departure from the main stem are unsolved problems4 ,the ,south ,american fossils have so far thrown little light into these dark places1 but they bear very cogent witness to the unity of origin of the five suborders1 which were most probably all derived from a single early ,eocene or ,paleocene group4 ,in the ,paleocene and through most of the ,eocene of ,north ,america there lived an order of mammals called the ,tniodontia 7or ,ganodonta7 which many of the foremost palontologists regard as an ancestral type of the ,edentata1 and ,dr4 ,schlosser actually includes them in that order4 ,that the tniodonts had certain striking resemblances to the edentates1 especially to the ground-sloths1 is not to be denied1 but the interpretation of these resemblances is a very complex and difficult question4 ,unfortunately1 no member of the order is known from an even approximately complete skeleton1 and therefore a discussion of the matter here would be unprofitable4 ,my own conclusion1 however1 may be stated1 to the effect that the supposed relationship of the tniodonts to the edentates is illusory and not real4 ,definite decision must await the finding of more complete material both of the tniodonts and the most ancient ,south ,american edentates4 ,,chapter ,,xvii ,,history ,,of ,,the ,,marsupialia ,the marsupials are a group of more primitive structure and greater antiquity than any which we have yet considered1 so primitive1 indeed1 that they are referred to a separate infraclass1 the ,didelphia or ,metatheria4 ,the order is one of very great variety in size1 form1 appearance1 diet and habits1 and mimics several of the higher orders in quite remarkable fashion4 ,herbivorous1 insectivorous and carnivorous forms are all numerous1 as well as arboreal1 terrestrial1 cursorial1 leaping and burrowing genera4 ,some are like hoofed mammals in appearance and the ,rodentia1 ,carnivora and ,insectivora are also closely imitated in externals4 ,with all this diversity1 most unusual within the limits of a single order1 there is such a unity of structure1 that a division of the group into two or more orders is impracticable4 ,at the present time1 marsupials are very largely confined to ,australia and adjoining islands1 where they constitute nearly the whole mammalian fauna1 and it is in the ,australian region that the remarkable diversity already mentioned is to be observed4 ,there are found the phalangers1 kangaroos1 bandicoots1 ,tasmanian 8devil0 and 8wolf10 and banded anteaters1 not to mention many other curious creatures4 ,in the western hemisphere only the opossums 7,didelphis1 ,chironectes7 and one very interesting relic of a long vanished assemblage1 ,cnolestes of ,ecuador and ,colombia1 are in existence to-day4 ,the opossums1 of which some twenty-three species are recognized1 have their headquarters in ,south ,america1 to which nearly all of the species are confined1 ,north ,america having but two or three4 ,the more important ,american marsupials are given in the table below3 ,suborder ,,polyprotodonta ,i4 ,,didelphiid4 ,opossums4 ,didelphis1 ,opossum1 ,pleist4 and ,rec41 ,n4 and ,s4 ,a4 ,chironectes1 ,water ,opossum1 ,rec41 ,s4 ,a4 ,peratherium1 low4 ,eoc4 to low4 ,oligo41 ,n4 ,a4 ,microbiotherium1 ,santa ,cruz4 ,eodidelphys1 do4 ,ideodidelphys1 ,casa ,mayor4 ,proteodidelphys1 ,cretaceous1 ,s4 ,a4 ,,ii4 ,,thylacynid4 ,predaceous ,marsupials4 ,cladosictis1 ,santa ,cruz4 ,amphiproviverra1 do4 ,prothylacynus1 do4 ,borhyna1 do4 ,proborhyna1 ,deseado4 ,pharsophorus1 do4 ,procladosictis1 ,casa ,mayor4 ,pseudocladosictis1 do4 ,suborder ,,diprotodonta ,,iii4 ,c,,nolestid4 ,cnolestes1 ,rec41 ,s4 ,a4 ,zygolestes1 ,paran4 ,palothentes1 ,santa ,cruz4 ,abderites1 do4 ,palpanorthus1 ,deseado4 ,,iv4 ,,garzoniid4 ,garzonia1 ,santa ,cruz4 ,halmarhiphus1 do4 ,cladoclinus1 do4 ,suborder ,,allotheria ,v4 ,,plagiaulacid4 ,polymastodon1 up4 ,cretac4 and ,paleoc41 ,n4 ,a4 ,ptilodus1 do4 ,neoplagiaulax1 ,paleoc41 ,n4 ,a4 ,,vi4 ,,polydolopid4 ,propolymastodon1 ,casa ,mayor4 ,polydolops1 do4 ,amphidolops1 do4 ,despite all their diversity of appearance and habits1 the unity of structure among the marsupials is such that the formation of groups of higher than family rank is very difficult1 and it is by no means certain that the suborders currently accepted correspond to the facts of actual relationship4 ,except in certain extinct ,south ,american genera1 there is very little change of teeth1 only the last premolar in each jaw being replaced4 ,sometimes the temporary tooth is long retained in function and1 more rarely1 it is shed very early2 while in several genera no replacement of teeth has been observed4 ,there is a difference of opinion among naturalists as to the proper interpretation of the marsupial dentition4 ,according to one view1 all except the replaced premolar belong to the milk-series and the permanent series has been lost2 the alternative and more probable belief is that the milk-dentition has been almost or completely suppressed4 ,whichever one of these interpretations be the right one1 there is strong reason to maintain that the very limited amount of change is not a primitive condition1 but a secondary one1 for a series of rudimentary teeth is formed before those which are to become functional4 ,the only reasonable explanation of such a condition is that it has been derived from one in which the normal succession and replacement of the teeth took place4 ,something of the same sort has been observed in the simplicidentate rodents4 ,the marsupial dentition differs from the placental one in the usual number of four molars1 instead of three1 and frequently also in exceeding the normal total number of #dd4 ,the incisors are almost always of a different number in the upper and the lower jaw and are frequently more numerous than in the placentals4 ,the skeleton has several diagnostic characters1 which are present throughout the order1 though one or other of these features may be absent in particular instances4 ,the skull has a very small brain-capacity and elongate face and jaws4 ,in the placental mammals1 the sutures between adjoining bones of the skull tend to close by cossification1 and the separate bones are clearly distinguishable only in young animals2 but in the marsupials the sutures remain open for a much longer period4 ,the lachrymal is expanded on the face and the foramen is outside of the orbit4 ,the tympanic is a mere ring and permanently separate from the other bones of the cranium1 while a false bulla is formed by the inflation of part of the alisphenoid4 ,in almost all marsupials there are large openings or vacuities in the bony palate4 ,one of the most characteristic and constant features of the marsupial skull is in the conformation of the angle of the lower jaw1 which is turned inward1 or inflected1 at nearly a right angle with the body of the jaw4 ,it is true that one existing ,australian genus has lost this character2 and in some of the placental orders1 especially the ,rodentia1 a somewhat similar structure may occasionally be found1 but it is never quite the same as in the marsupials1 in which it goes back to a remote antiquity4 ,there are very constantly #ai trunk-vertebr1 of which usually #ac are dorsals4 ,the tail differs greatly in length in the various genera1 but most of them have well-developed tails4 ,an additional pair of elements1 besides the three which are found in the placentals1 enter into the composition of the hip-bones2 these are the marsupial bones1 slender1 flattened rods1 directed forward in the abdominal wall and diverging in ,v-shape4 ,save in a few genera1 clavicles are present and of full size4 ,the humerus may or may not have the epicondylar foramen1 but the femur never has the third trochanter4 ,the feet vary greatly in form and structure1 in accordance with the habits1 but there is a very widespread adaptation to an arboreal life1 and even in terrestrial and burrowing forms more or less distinct traces of this arboreal adaptation may be noted4 ,this fact has led to a generally accepted inference that all existing marsupials had an arboreal ancestry4 ,the soft parts and more especially the organs of reproduction are likewise very characteristic1 and one or two of these peculiarities may be mentioned4 7#a7 ,in the female1 the vagina is double and on the abdomen is the pouch1 or marsupium 7which gives its name to the order71 a hair-lined bag1 opening either forward or backward1 which serves to carry the young and into which the teats open4 ,a considerable number of species have lost the marsupium1 while other species of the same genera retain it1 and there can be little question that its absence is a secondary condition4 7#b7 ,except in one modern ,australian genus1 the marsupials have no true placenta1 and the young are born in a very immature state1 incapable of even swallowing4 ,the new-born young are transferred to the nipples of the mother and are attached to these and fed by the pumping of milk into their mouths by muscular action of the mother4 ,a special1 though temporary1 arrangement of the gullet and windpipe is provided1 so that the helpless young animal shall not be suffocated by the entrance of milk into the lungs4 ,,suborder ,,polyprotodonta ,this suborder1 as is indicated by its name1 is characterized by its numerous incisors1 which are #e_/d1 or #d_/c1 and none of them is especially enlarged2 by the large canines in both jaws1 simple premolars and tritubercular upper molars4 ,the members of this group are carnivorous or insectivorous in habit1 and all the existing ones are of small or moderate size1 though some very large extinct forms are known4 ,except in one ,australian family1 the feet are not 8syndactyl10 a term which means the enclosure of two or more digits in one fold of skin4 ,the only existing ,american representatives of the suborder are the opossums1 the great majority of which are ,neotropical in distribution4 #a4 ,didelphiid4 ,opossums ,in this family the dental formula is3 i #e_/d1 c #a_/a1 p #c_/c1 m #d_/d1 #b #ej4 ,the incisors are small and closely crowded together1 the canines large and tusk-like1 the premolars simple and of compressed-conical form2 in existing species1 the upper molars are triangular1 each of the three main cusps is ,v-shaped and there are additional minute cusps along the outer border2 the lower molars have a high anterior triangle of three pointed cusps and a low heel with several distinct cusps4 ,the humerus has an epicondylar foramen and the feet are five-toed2 in the manus all the digits are armed with claws and the thumb is but partially opposable1 while in the pes the hallux is without a claw and completely opposable1 making the foot much like that of a monkey4 ,the division of the existing opossums into genera has caused much difference of opinion and practice among naturalists2 there are five groups1 which by some are regarded as genera1 and by others as subgenera1 all modern members of the family being very much alike4 ,the species ,didelphis marsupialis1 which is common in the eastern ,united ,states and extends through temperate ,north ,america1 ,central ,america and tropical ,south ,america1 has a complete pouch and is chiefly arboreal and insectivorous in habit4 ,in the woolly opossums 7,caluromys7 there is no pouch1 and the young1 when sufficiently advanced1 are carried on the mother's back1 winding their tails around hers4 ,in both of these genera the tail is long1 naked and prehensile1 but in the tiny species of ,peramys the tail is short and hairy4 ,another ,neotropical genus1 ,chironectes1 the ,yapock or ,water ,opossum1 is the only existing instance of an aquatic marsupial4 ,it has light grey fur1 striped with brown1 and webbed hind feet2 living chiefly in the water1 it feeds upon crayfish1 water-insects and small fish4 ,the derivation of the modern ,north ,american opossums is a matter of great uncertainty4 ,the present distribution of the family1 with by far the greater number of its species confined to the ,neotropical region1 is certainly suggestive of a ,south ,american origin1 but such considerations are very untrustworthy guides in tracing the history of animal groups4 ,no opossum has been found in any ,north ,american formation between the ,pleistocene and the lower ,oligocene1 though in the case of such small animals1 negative evidence must be accepted with caution4 ,in the ,white ,river ,oligocene many minute opossums have been found and referred to the ,european genus ,peratherium1 though it so closely resembles the modern ,didelphis that many systematists do not make the distinction4 ,in the ,eocene1 ,paleocene and upper ,cretaceous1 opossums were represented doubtfully2 the material is too incomplete for assured determination2 in ,europe they existed in the ,oligocene and upper ,eocene4 ,in ,south ,america the family went back uninterruptedly to the oldest mammal-bearing beds of ,patagonia1 which may be upper ,cretaceous4 ,the opossums are thus the remnants of an exceedingly ancient group1 whose beginnings are to be sought in the ,mesozoic era and which was probably spread over all the continents4 ,to all appearances1 the whole group vanished completely from the northern hemisphere1 but rentered ,north ,america from the south at some time during the ,pliocene or early ,pleistocene and permanently established itself here4 ,the opossums are the most primitive of existing marsupials1 especially the little ,south ,american genus1 ,marmosa1 and are regarded1 by some of the most competent students of the order1 as closely representing the ancestral type of all the ,recent families and genera1 both of the ,polyprotodonta and ,diprotodonta4 #b4 ,thylacynid4 ,predaceous ,marsupials ,by many naturalists this group of flesh-eating forms is included in the ,dasyurid4 ,the family never entered ,north ,america1 but played a very important part in the ,tertiary of ,south ,america4 ,three existing genera of the ,australian region throw considerable light upon the ,south ,american types1 and therefore some account of them will not be out of place here4 ,the largest of modern predaceous marsupials is the animal 7,thylacynus cynocephalus7 erroneously1 but very naturally1 called the 8,tasmanian ,wolf10 now confined to ,tasmania1 but occurring also in the ,pleistocene of ,australia4 ,as 8wolf0 applied to a marsupial is misleading1 it will be less confusing to employ the anglicized form of the generic name 8,thylacine40 ,this animal is of the size of the small ,prairie ,wolf or ,coyote 7,canis latrans7 and has very wolf-like appearance and habits4 ,the muzzle is long and pointed1 the ears erect and rather small1 the tail long1 very thick at the base and tapering to the end1 not bushy1 but covered with short1 close-set hairs2 the colour is greyish brown1 with dark1 transverse stripes on the posterior half of the back and base of the tail4 ,apparently the creature is in process of losing its stripes and acquiring the solid body-colour4 ,the dental formula is3 i #d_/c1 c #a_/a1 p #b_/b1 m #d_/d1 #b #df2 the incisors are small1 the canines large fangs1 and the premolars simple2 the upper molars are tritubercular1 with large inner cusp and postero-external cutting ridge1 and the lower molars are trenchant1 with low heel4 ,the whole dentition is remarkably like that of many ,eocene creodonts1 such as ,sinopa and ,tritemnodon 7see p4 #eff74 ,the milk-premolar is small and functionless and is shed very early4 ,the skull is very wolf-like in appearance1 but thoroughly marsupial in structure1 and has the large palatal vacuities common in the order4 ,the marsupial bones do not ossify and are evidently on the point of disappearance4 ,there are five digits in the manus1 four in the pes1 the hallux being completely suppressed4 ,in habits1 the ,thylacine is carnivorous and so destructive to sheep that the farmers have nearly exterminated it4 ,illustration3 ,,fig4 #bif4--,thylacine1 or 8,tasmanian ,wolf0 7,thylacynus cynocephalus74--,by permission of ,w4 ,s4 ,berridge1 ,london4 ,the other forms to be mentioned belong to the closely allied family of the ,dasyurid4 ,the 8,tasmanian ,devil0 7,sarcophilus ursinus7 is now1 like the ,thylacine1 confined to ,tasmania1 but remains of it have been found in the ,australian ,pleistocene2 it has one less premolar in each jaw1 giving the formula3 i #d_/c1 c #a_/a1 p #b_/b1 m #d_/d1 #b #db2 there is no milk-tooth4 ,the premolars are closely crowded and the molars resemble those of the ,thylacine in construction1 but are broader and heavier4 ,the skull is disproportionately large1 with shorter and wider muzzle and jaws than in the ,thylacine2 the tail is of only moderate length and somewhat shaggy2 the hallux is wanting4 ,in size and build1 the ,tasmanian ,devil resembles a badger and has long and heavy fossorial claws on the fore feet2 the hair is rough and shaggy1 black in colour with white patches4 ,the animal has received its name from its fierce and savage disposition and is almost as destructive to sheep as the ,thylacine4 ,the five species of ,dasyurus are distributed through ,tasmania1 ,australia and ,new ,guinea and are called 8,native ,cats02 they are much smaller animals than the two preceding genera1 not exceeding a domestic cat in size4 ,as the ,thylacine imitates a wolf and the ,tasmanian ,devil a badger1 the dasyures resemble the civets4 ,in them the dental formula is the same as in ,sarcophilus1 but the teeth have higher and sharper cusps4 ,the head has a narrow1 tapering muzzle and narrow ears2 the body is long and the tail of moderate length4 ,the limbs are short and slender and a small hallux is present in some of the species4 ,the fur is grey or brown1 with numerous white spots1 and the tail is covered with long hair1 but not bushy4 ,the dasyures are largely arboreal and prey upon small mammals1 birds and eggs4 ,until the arrival of the true ,carnivora from the north1 their rle was taken in ,south ,america by predaceous marsupials1 which persisted as late as the presumably ,pliocene beds of ,monte ,hermoso4 ,little is known of them in that stage1 however1 or in the older ,paran1 but abundant material representing those of the ,santa ,cruz has been collected4 ,among these there was a considerable range of size and some variety of structure1 and they all differed in certain respects from the modern ,australian genera1 differences which have led some authorities to deny the marsupial character of all these ,south ,american forms4 ,the differences are of three kinds3 7#a7 there are no vacuities in the bony palate2 7#b7 the milk-dentition is less reduced1 the canines and one or two premolars being changed2 7#c7 the enamel of the teeth1 in the only genus 7,borhyna7 which has been examined microscopically1 resembles in its minute features that of the placentals and lacks the marsupial characters4 ,though by no means unimportant1 these differences are altogether outweighed by the thoroughly marsupial nature of all other parts of the skeleton1 and ,i cannot but agree with ,dr4 ,sinclair#bj in including them in the same family with the ,tasmanian ,thylacine4 ,the genus ,prothylacynus was especially like the latter and must have had a very similar appearance1 though in the restoration 7,fig4 #big7 the colour-pattern is changed to one of longitudinal stripes1 as more probably pertaining to so ancient and primitive a form4 ,the humerus had the epicondylar foramen1 and a large vestige of the hallux was retained1 though it could not have been visible in the living animal4 ,a more specialized ,santa ,cruz genus was ,borhyna 7,fig4 #bdd1 p4 #did71 an animal of about the same length and height as ,prothylacynus and the ,thylacine1 but much more massive and powerful4 ,the skull was remarkable for the small size of the brain-case and the great spread of the zygomatic arches1 which gave a rounded and almost cat-like appearance to the head1 as is shown in the restoration 7,fig4 #bdd74 ,in this genus the upper incisors were reduced to three1 a very unusual thing among the ,polyprotodonta1 and the humerus had lost the epicondylar foramen4 ,prothylacynus and ,borhyna were the largest of the ,santa ,cruz flesh-eaters and no doubt pursued the smaller and more defenceless ungulates1 but were hardly sufficiently powerful to attack successfully the larger hoofed animals1 which were probably well able to defend themselves4 ,illustration3 ,,fig4 #big4--,santa ,cruz predaceous marsupial 7,prothylacynus patagonicus7 and typothere 7,interatherium robustum74 ,restored by ,c4 ,knight from skeletons in the museum of ,princeton ,university4 ,illustration3 ,,fig4 #bih4--,skull of ,borhyna1 ,santa ,cruz4 7,after ,sinclair1 ,reports ,princeton ,university ,expeditions to ,patagonia1 ,vol4 ,,iv47 ,illustration3 ,,fig4 #bii4--,skull of small predaceous marsupial 7,amphiproviverra manzaniana71 showing the punctured wound from a bite4 ,princeton ,university ,museum4 ,associated with these larger predaceous marsupials were several much smaller kinds1 ranging in size from a fox to a weasel1 which must have preyed upon the abundant rodents and other small mammals and birds4 ,one of these 7,amphiproviverra7 had an opposable hallux1 somewhat as in the opossums1 and was therefore probably arboreal4 ,an interesting specimen in the museum of ,princeton ,university illustrates the pugnacity of these small creatures2 it is a skull in which the left upper canine was completely torn out1 the circular puncture of the enemy's bite being unmistakable and the healed edges of the wound proving that the loss of the tooth was suffered during life4 ,in structure1 these smaller animals differed so little from the larger ones1 that no particular description of them is needed4 ,in the restoration of ,cladosictis 7,fig4 #cjj7 the spotted pattern of the ,australian dasyures1 or native cats1 has been taken as a model4 ,in the ,deseado formation the predaceous marsupials have been less abundantly found than in the ,santa ,cruz and there can be little doubt that the group is very inadequately represented by the material so far collected4 ,only two genera1 known from lower jaws1 have been described1 but one of these 7,proborhyna7 is of interest because of its enormous size1 far surpassing any of the ,santa ,cruz forms and equalling the largest modern bears4 ,this is another illustration of the unusual relationship between the ,deseado and ,santa ,cruz faunas1 the older stage so frequently having the larger animals4 ,predaceous marsupials of small size may be traced back to the ,casa ,mayor formation1 but very little is yet known of them4 ,there is no obvious difficulty in the way of their derivation from opossum-like forms1 such as are found in the ,cretaceous of ,north ,america and probably of ,south ,america also4 ,the relation of the ,south ,american to the ,australian marsupials offers problems of unusual interest1 a discussion of which would be impracticable here4 ,several alternative solutions of the problem have been offered and great differences of opinion exist with regard to it4 ,to my mind the most probable suggestion is that a land-connection1 by way of the ,antarctic continent1 existed in early ,tertiary times1 by means of which the ancestors of the ,australian marsupials migrated1 from ,south ,america1 though this explanation is rejected by several eminent authorities4 ,illustration3 ,,fig4 #cjj4--,small predaceous marsupial 7,cladosictis lustratus7 and rabbit-like typothere 7,pachyrukhos moyani71 ,santa ,cruz stage4 ,restored by ,c4 ,knight from skeletons in ,princeton ,university and the ,american ,museum of ,natural ,history4 ,,suborder ,,diprotodonta ,north ,america never had any representatives of this suborder1 but ,south ,america possessed many of them in the ,santa ,cruz ,miocene and one genus 7,cnolestes7 has survived to the present time4 ,australia1 on the other hand1 has three well-defined families of the suborder1 the kangaroos1 phalangers and wombats1 but no member of any of these has ever been found outside of the ,australian region4 ,so far as we know1 therefore1 the suborder is and always has been confined to the southern hemisphere4 ,illustration3 ,,fig4 #cja4--,skull of ,cnolestes obscurus1 enlarged4 7,after ,sinclair47 ,the modern ,south ,american genus ,cnolestes is a small1 rat-like animal and very rare2 it has been found only in ,ecuador and ,colombia4 ,its dentition is not at all typically diprotodont1 but rather intermediate in character between the latter and the ,polyprotodonta4 ,the dental formula is3 i #d_/c1 c #a_/a1 p #c_/c1 m #d_/d1 #b #df4 ,the upper incisors are small and of subequal size1 though the second is somewhat the largest of the series1 and the canine is considerably larger and more prominent than any of them4 ,the foremost lower incisor is long and pointed and directed almost straight forward2 the other lower incisors and the canine are minute and can have little or no functional value4 ,the premolars are small and simple and the upper molars quadritubercular1 the third one triangular1 and the fourth very small and apparently about to disappear4 ,such teeth would seem to indicate a vegetable diet1 but it is reported that the animal subsists chiefly upon small birds and their eggs4 ,the skull1 which is typically marsupial in all its characters1 is most like that of the smaller ,australian native cats 7,dasyurid7 and the feet show no signs of the syndactyly which all the other diprotodonts display so clearly4 ,dr4 ,gregory is 8inclined to regard ,cnolestes and its allies as an independent suborder1 an offshoot of primitive ,polyprotodonts which has paralleled the ,diprotodonts in certain characters of the dentition40#ba ,illustration3 ,,fig4 #cjb4--,lower jaws of ,santa ,cruz cnolestids1 enlarged4 ,a1 ,garzonia patagonica4 ,b1 ,abderites crassignathus4 ,c1 ,callomenus ligatus4 7,after ,sinclair1 in ,reports ,princeton ,university ,expeditions to ,patagonia1 ,vol4 ,,iv47 ,evidently1 the animals of this series were extremely rare or absent in the areas where the known ,south ,american deposits of the ,pleistocene and ,pliocene were laid down1 for there is a very long hiatus in their history from the ,recent to the ,santa ,cruz1 during which none has yet been found1 except one genus 7,zygolestes7 in the ,paran4 ,in the ,santa ,cruz1 however1 there was a great abundance of these little marsupials1 to which various generic names have been given and which displayed considerable variety in the forms of the teeth4 ,some 7e4g4 ,garzonia7 agreed with ,cnolestes in having no trenchant shearing teeth2 behind the large1 procumbent lower incisor1 followed four or five very minute teeth1 which must have been nearly or quite functionless1 succeeded by the well-developed molars4 ,other genera 7e4g4 ,abderites7 had a similar dentition1 with the important exception that the last upper premolar and first lower molar were enlarged and trenchant1 together forming a shearing pair2 these teeth were vertically fluted or ribbed in very characteristic fashion4 ,the ,australian phalangers have very similar trenchant and fluted teeth1 but in that family the lower one of the pair is the last premolar1 not the first molar4 ,marsupials of this type have not been found in formations older than the ,deseado4 ,the relationship of these ,south ,american genera to the ,australian phalangers is a very interesting question from the standpoint of mammalian distribution1 but is not likely to receive a positive answer until something is learned regarding the history of the ,australian family4 ,,suborder ,,allotheria ,illustration3 ,,fig4 #cjc4--,skull of ,paleocene allothere 7,ptilodus gracilis71 enlarged1 ,fort ,union stage4 7,after ,gidley47 ,this extinct suborder is still very imperfectly understood1 for it is known almost exclusively from jaws and teeth2 so far1 the skull of one genus and most of that of another have been obtained1 but hardly anything of the skeleton4 ,the ,allotheria were small or minute marsupials1 herbivorous or omnivorous1 which had lost all trace of the canines and had one pair of incisors above and below1 which grew from persistent pulps and had a scalpriform1 rodent-like character4 ,the molars were composed of numerous tubercles 7whence the name 8,multituberculata10 often applied to the group7 arranged in two or three longitudinal rows1 and the premolars were either like the molars1 but of simpler pattern1 or compressed1 sharp-edged and trenchant4 ,the ,allotheria were among the most ancient of mammals and have been found in the ,triassic of ,europe1 the ,jurassic of ,europe and ,south ,africa1 the ,jurassic and ,cretaceous of ,north ,america and the ,paleocene of both northern continents1 while the ,south ,american ,eocene 7,casa ,mayor7 had certain problematical genera 7,polydolopid71 which may be referable to the ,allotheria or to the ,cnolestes series4 ,the suborder was thus preminently a ,mesozoic one and1 with the doubtful exception of ,south ,america1 it is not known to have passed beyond the limits of the ,paleocene4 ,there is not the least likelihood that any existing mammals were derived from the ,allotheria4 ,illustration3 ,,fig4 #cjd4--;,head of ,ptilodus gracilis1 about natural size4 ,restored from a skull in the ,united ,states ,national ,museum4 ,while the ,allotheria have an antiquity at least equal to that of any other mammals known1 there were other groups in the ,jurassic and ,cretaceous1 which1 so far as may be judged from teeth alone1 would seem to have been ancestral to the other marsupials and to the placentals4 ,it would serve no useful purpose to describe these minute creatures1 which are so very incompletely known1 though to the specialist they are of the highest interest4 ,the genera found in the ,triassic of ,north ,carolina may or may not represent the primitive mammalian stock4 99 99 99 99 99 ,the question of the origin of the ,mammalia is still involved in great obscurity1 and the most divergent opinions are held concerning it4 ,it remains an unsolved problem whether the mammals were all descended from a common stock1 or have been derived from two independent lines of ancestry1 or1 in technical phrase1 whether the class is monophyletic or diphyletic4 ,assuming1 as seems most probable from present knowledge1 that the mammals are monophyletic1 the question next arises3 ,from what lower vertebrates are they descended8 ,a great controversial literature has grown up around this problem1 one party regarding the ,amphibia and the other the ,reptilia as the parent group4 ,the palontological evidence1 while not conclusive1 is decidedly in favour of the latter view4 ,in the ,triassic of ,south ,africa is found a group of reptiles which approximated the mammals very much more closely than do any other known representatives of the lower vertebrates4 ,while it is not believed that any of these ,triassic reptiles were directly ancestral to the mammals1 they did1 to a very great extent1 bridge the gap between the two classes and show us what the reptilian ancestors of the mammals were probably like4 ,with perhaps the exception of certain ,insectivora1 the ,paleocene faunas contained few1 if any1 ancestors of modern mammals4 ,these originated in some region which has not been identified1 but may be plausibly conjectured to be central ,asia1 whence they migrated westward to ,europe and eastward to ,north ,america1 reaching both of those continents in the lower ,eocene4 ,from that time onward they increased and multiplied1 becoming more and more differentiated through divergent evolution1 until the existing state of things was attained4 ,from the lower ,eocene we are on firm ground1 and1 though very much remains to be learned1 much has already been accomplished in the way of tracing the history and development of many mammalian orders4 ,it has been my endeavour in the body of this book to sketch the better established and more significant parts of this marvellous story4 ,,chapter ,,xviii ,,modes ,,of ,,mammalian ,,evolution ,throughout this book the theory of evolution has been taken for granted1 as it seemed superfluous to present an outline of the evidence upon which that theory rests4 8,descent with modification0 is now accepted among naturalists with almost complete unanimity1 but1 unfortunately or otherwise1 this general agreement does not extend beyond the point of believing that the present organic world has arisen by descent from simpler and simpler forms4 ,the application of the theory to concrete cases is beset with grave difficulties and gives rise to the most divergent views4 ,the uninitiated reader who takes up a treatise upon some animal group may well be surprised to see the apparently minute accuracy with which the genealogy of the series is set forth and the complex relationships of its members marshalled in orderly array4 ,another treatise on the same subject1 however1 while agreeing perfectly with the first as to the facts1 will contradict its conclusions in almost every particular4 ,indeed1 so notorious did this become1 that 8phylogenetic trees0 were rather a laughing-stock1 and most naturalists lost interest in the problems of phylogeny and turned to fields that seemed more promising4 ,to some extent1 this almost hopeless divergence is inherent in the very nature of the problem1 which deals with the value of evidence and the balancing of probabilities1 as to which men must be expected to differ2 but there is another and more potent cause of the discrepancy4 ,when the contradictory schemes are analyzed1 it is seen that each is founded upon certain assumptions regarding the evolutionary process1 assumptions which are generally implicit and often apparently unconscious4 ,in the present state of knowledge1 these postulates are1 for the most part1 matters of judgment1 incapable of definite proof1 and they appeal with very different force to different minds2 what to one seems almost self-evident1 another regards as all but impossible4 ,it will1 however1 be of service to examine such of these postulates as are involved in mammalian history4 ,it is quite impracticable to construct a genetic series without making certain assumptions as to the manner in which the developmental process operated and the kinds of modification that actually did occur4 ,in the preceding chapters1 which deal with the evolutionary history of various mammalian groups1 it was repeatedly stated that1 of two contemporary genera1 one was to be taken as the ancestor of some later form and the other regarded as a collateral branch1 but it was also pointed out that in certain cases1 palontologists differed more or less decidedly as to the proper interpretation of the facts2 it is just this lack of agreement as to the modes and processes of change that forms the root of the difficulty4 ,there are instructive analogies between the history1 aims and methods of comparative philology1 on the one hand1 and zology1 on the other4 ,in both sciences the attempt is made to trace the development of the modern from the ancient1 to demonstrate the common origin of things which are now widely separated and differ in all obvious characteristics1 and to determine the manner in which these cumulative modifications have been effected4 ,at the present time zology is still far behind the science of language with regard to the solution of many of these kindred problems and has hardly advanced beyond the stage which called forth ,voltaire's famous sneer3 8,l'tymologie est une science ou les voyelles ne font rien et les consonnes fort peu de chose40 ,many of the animal genealogies which have been proposed have no better foundation than the 8guessing etymologies0 of the eighteenth century1 and for exactly the same reason4 ,just as the old etymologists made their derivations upon the basis of a likeness of sound and meaning in the words compared1 so the modern zologist1 in attempting to trace the relationships of animals1 must proceed by balancing their similarities and differences of structure4 ,the etymologist had no sure test for distinguishing a true derivation from a plausible but false one1 and the zologist finds himself in the same predicament4 ,how much weight should be allowed to a given likeness and how far it is offset by an accompanying difference1 there are no certain means of determining1 and we are still in search of those laws of organic change which shall render such service to zology as ,grimm's law did to the study of the ,indo-,european languages4 ,doubtless1 the analogy may be pushed still farther1 and it may be confidently assumed that1 just as sound principles of etymology were established by tracing the changes of words step by step from their modern forms to their ancient origins1 so the existing animal forms must be traced back through the intermediate gradations to their distant ancestors1 before the modes of organic development can be deduced from well-ascertained facts4 ,the evolutionary problem has been attacked by the aid of several distinct methods1 each of which has its particular advantages and its peculiar limitations and drawbacks4 ,most of the methods suffer from the fact that they deal only with the present order of things1 and thus resemble the attempt to work out the derivations of languages that have no literature to register their changes4 7#a7 ,of necessity1 the oldest of these methods is ,comparative ,anatomy1 which had made great advances in pre-,darwinian days4 ,it is the indispensable foundation of the whole inquiry1 for an accurate knowledge of ,comparative ,anatomy is absolutely necessary to the use of the other methods2 in the hands of the great masters it has registered many notable triumphs in determining the mutual relationships of animal groups2 but finality cannot be reached by this method1 because it deals only with existing forms and possesses no sure criterion for determining the value of similarities4 ,it is thus unable to distinguish with certainty between those resemblances which are due to inheritance from a common ancestry and those which have been independently acquired4 ,it is a very frequent fallacy to assume that1 because two allied groups1 ,b and ,c1 possess a certain structure1 their common ancestor1 ,a1 must also have possessed it4 ,this may or may not have been the case1 and ,comparative ,anatomy offers no assured means of deciding between those alternatives or of confidently distinguishing primitive characters from degenerative or retrograde changes4 7#b7 ,embryology1 which is the study of the development of the individual animal from the unfertilized egg to the adult condition1 was long regarded as the infallible test of theoretical views in zology4 ,this was on the assumption that individual development 7ontogeny7 is a recapitulation in abbreviated form of the ancestral history 7phylogeny7 of the species1 and was called by ,haeckel 8the fundamental biogenetic law40 ,it was soon learned1 however1 that the 8recapitulation theory0 was not to be implicitly trusted1 for structural features which could not possibly be a part of ancestral history were imposed upon or substituted for those due to phylogenetic inheritance4 ,now the whole theory is strongly questioned1 and the absence of any universally accepted rules of interpretation1 by which the contradictory embryological data may be harmonized into a consistent whole1 has deprived the method of that authoritative character once so generally ascribed to it4 ,it is like dealing with a literature which has been vitiated with many forgeries1 only the grossest of which can be readily detected4 ,embryology has rendered many great services in the solution of zological problems and will no doubt render many more1 but it cannot1 of itself1 reach final conclusions4 7#c7 ,experimental ,zology1 especially that part known as 8,genetics10 one of the newest and most promising provinces of the science1 has already taught us much concerning the laws of inheritance and the manner in which new characters arise1 and no one can venture to fix the limits of its possible results4 ,on the other hand1 it does not seem likely that the larger problems of relationship and classification can be solved by this method1 because of the brief time which the shortness of human life allows for the experiments4 7#d7 ,palontology suffers from the drawback that much of the past history of life is irretrievably lost1 and even when the record is remarkably complete1 as it is for certain chapters of the history1 the material is but partially preserved4 ,with such rare exceptions as are of little practical importance1 only the hard parts1 bones1 teeth1 etc41 are retained and the soft parts completely destroyed4 ,nevertheless1 ,palontology has the preminent advantage of offering to the student the actual stages of development1 and thus1 to recur to the simile of language1 has preserved original documents and in the true order of succession4 ,it is true that it is well-nigh impossible to reconstruct a phylogenetic series of ancestor and descendant1 unaffected by theoretical preconceptions1 and the differences which arise in the interpretation of undisputed facts are caused by divergent beliefs concerning the actual course of the evolutionary process4 ,if final and definitive results are ever to be reached1 it must be through the coperation of all the methods of research1 and such results must be able to stand the tests applied by every sound method4 ,on the other hand1 the study of those phylogenetic series which are generally accepted as well established1 should furnish us with some fairly definite information as to the modes in which development has operated in the past1 since the order of succession in time fixes a limit to the rearrangement of related series4 ,some of the conclusions thus suggested may be stated here4 ,i4 ,one of the most fundamental problems concerning the course of development is that which deals with parallel and convergent evolution4 ,the term parallelism implies that forms having a common origin may independently run through a similar course of development and arrive at similar results4 ,illustrations of this principle are given by the many phyla of horses1 rhinoceroses and camels1 which persisted side by side through several geological stages1 following independent1 but parallel1 courses of change4 ,an even more striking case is that of the two subfamilies of the cats1 the true felines and the sabre-tooths4 ,whatever view may be taken of the relationships of these two groups1 it is clear that1 at least from the upper ,oligocene to the ,pleistocene1 they were separate1 but kept remarkably even pace with each other in their advance and specialization4 ,by convergence is meant a similar result which is reached by two or more independent lines having different starting points1 so that the descendants are more alike than were the ancestors1 and is thus the opposite of divergence1 the result of which is to make the descendants of common ancestors less and less alike with each succeeding stage4 ,either parallelism or convergence may be involved in the independent acquisition of similar characters1 of which these are so many examples4 ,it is obvious that this problem is fundamental and that little real progress is possible until a solution is reached4 ,as to the correct solution1 there is much difference of opinion among naturalists4 ,some deny altogether the reality and importance of these modes of development1 but such are almost exclusively concerned with the modern world2 others go to the opposite extreme1 and looking upon every large group as polyphyletic1 consider parallel and convergent development to be the rule of evolution4 ,few palontologists are disposed to doubt that these modes of evolution are very frequent2 their difficulty is to determine what limits can be drawn1 and this difficulty can be removed only by much wider and more exact knowledge than we now possess4 ,so far as single structures are concerned1 the fossils demonstrate unequivocally that they have been independently acquired in a great many cases4 ,the resultant similarity may be attained through the loss1 the acquisition or the modification of parts4 ,the reduction of toes from the primitive number of five to four1 three1 two1 or even one1 has happened over and over again in the most diverse groups4 ,there is good reason to believe that all the early and primitive placental mammals had the third trochanter on the femur and the epicondylar foramen on the humerus1 but in most of the modern groups these structures are lost2 and the list of such similar reductions of parts might be almost indefinitely extended4 ,of much greater significance is the independent similar modification of parts and acquisition of new structures4 ,innumerable examples of this kind of parallel and convergent development might be given1 but a few will be sufficient to illustrate the principle4 7#a7 ,the odontoid process of the axis 7second vertebra of the neck7 was primitively a bluntly conical peg1 a form which is still retained in the great majority of mammals1 but in the true ruminants1 the camels1 the horses and the tapirs1 the process is spout-shaped1 concave on the upper side1 convex on the lower4 ,by tracing the development of those groups1 it has been conclusively demonstrated that the change of form took place independently in each of the four4 7#b7 ,the ruminants have molar teeth composed of four crescentic cusps arranged in two transverse pairs1 the pattern called selenodont4 ,the evidence is very strong that this highly characteristic molar pattern has been several times independently repeated1 as in the true ruminants1 the camels1 the oreodonts and probably other groups also4 7#c7 ,the family ,macrauchenid of the extinct ,litopterna shares with the camel tribe the remarkable peculiarity of having the canal for the vertebral artery running through the neural arches of the neck-vertebr4 7#d7 ,a very striking instance is afforded by the three widely separated groups of hoofed animals1 members of which had their hoofs transformed into claws2 the chalicotheres arose from the normal perissodactyls 7p4 #cef71 the agriochrids from the oreodonts and the ,entelonychia from the toxodonts4 ,from time to time attempts have been made to unite two or more of these groups1 but in each case better material and fuller knowledge have demonstrated the unnatural character of such association and the separate origin of the peculiar structure4 ,admitting the reality and frequency of these modes of development1 a far more difficult problem is to determine the extent to which such independent acquisition of similar structures has actually been carried1 and it is at this point that the widest divergences of opinion are to be found4 ,as yet1 our knowledge is far too imperfect to permit the making of positive statements1 but there is no evidence which would justify the conclusion that the same genus1 family or order of mammals ever arose independently from radically different ancestors4 ,we have no reason to believe that identical groups of mammals were ever separately developed in land areas which through long periods of time had no means of intercommunication4 ,if such a thing ever happened1 it must have been the rarest of exceptions4 ,on the other hand1 parallelism1 by which related forms pass through similar stages of development1 would seem to have been so exceedingly common1 as fairly to deserve being called a normal method of evolution4 ,as more and better material has been gathered1 it has grown increasingly clear that almost every large group of generic1 family or higher rank1 whose history is known in any adequate measure1 consists of several distinct1 though related phyla1 which pursued more or less closely parallel courses of modification1 though diverging from one another sufficiently to make the distinction of them comparatively easy4 ,the parallelism was thus not exact1 however perfect it may have been in particular structures1 and the longer the phyla persisted1 the more distinctly did they diverge4 ,a typical problem1 which involves these principles1 is afforded by the very curious and interesting group of ,south ,american hoofed animals known as the ,litopterna 7,chap4 ,,xiii74 ,the many remarkable resemblances between these ungulates and the perissodactyls and1 more specifically1 between the family ,proterotheriid and the horses1 have been very differently interpreted by palontologists4 ,some have insisted that the ,litopterna should be merged in the ,perissodactyla1 on the ground that such a degree of likeness could not have been independently acquired4 ,others hold that this is a remarkable case of parallelism or convergence1 and the latter is1 in my opinion1 much the more probable view4 ,until the ancestry of both groups1 ,perissodactyla and ,litopterna1 shall have been definitely ascertained1 it will not be practicable to make a final decision between these alternatives1 nor1 if the similarities were really independently acquired1 to determine whether parallel or convergent evolution is involved4 ,it is quite possible that both groups were rooted in the common ground of the ,condylarthra1 and1 if so1 their relation is one of parallelism2 but no such common ancestry has been proved1 and it is equally possible that their ancestry was totally distinct4 ,in the latter case the resemblances were due to convergence4 ,assuming that the remarkable resemblances between the ,proterotheriid and the horses were separately acquired1 it should be emphasized that these similarities nowhere amount to identity4 ,the likenesses are not confined to a few structures1 but are general throughout the skeleton and may be noted in the teeth1 skull1 trunk1 limbs and feet1 but in every single one of these parts the similarities are offset by differences of great significance4 ,no competent anatomist would mistake any of the bones of the proterotheres for the corresponding parts of the horses1 whatever view he might hold as to the relationship between the two groups4 ,the case is thus one of a very instructive kind1 as tending to show that identity of structure in so highly complex creatures as mammals is not independently attained by widely separated or entirely unrelated forms4 ,probable as this conclusion is made by all the available evidence1 it cannot be regarded as demonstrated2 it is proverbially impossible to prove a negative4 ,on the other hand1 it is equally probable that nearly related forms do very frequently1 perhaps normally1 pass through separate1 but closely similar1 courses of development4 ,it is likely that a new species is usually formed through similar and simultaneous modification of many individuals1 rather than from a single individual or pair4 ,it may be the general rule1 as almost certainly has often happened1 that a new genus arises by the separate assumption of the new character by several species of the ancestral genus1 rather than through the rapid diversification of a single species1 though1 no doubt1 parallel and divergent modification are both very frequent and important processes4 ,dr4 ,eigenmann concludes from his study of ,south ,american fresh-water fishes that a certain new genus is even now in process of origin through the transformation of several species of an older genus1 which in different parts of the continent are simultaneously1 but independently1 taking on the new character4 ,sometimes it is possible to assign a definite reason for the independent origin of similar structures in different groups of mammals4 ,except for the head1 there is much similarity of appearance among the very massive hoofed animals1 such as the elephants1 rhinoceroses1 tapirs and hippopotamuses of the present time1 a fact which induced ,cuvier to unite them in one order1 the 8,pachydermata10 a term which has passed into vernacular1 if metaphorical1 usage4 ,no doubt also1 several extinct groups1 such as the ,amblypoda and the perissodactyl family of the ,titanotheriid1 would have been included1 had they been known in ,cuvier's day4 ,in the largest and heaviest of these animals1 the elephants1 amblypods and titanotheres1 there are many close correspondences in all parts of the skeleton1 which are clearly due to the mechanical necessities imposed by the support of immense weight1 and the developmental history of each group shows that the smaller and lighter ancestors were less similar than the larger and more massive descendants4 ,such subsequently acquired likenesses are thus obvious examples of convergence and were caused by adaptation to similar needs4 ,frbringer has shown that among birds size and weight of body determine many resemblances between unrelated families1 the largest forms displaying a more advanced grade of specialization4 ,it is thus extremely probable that evolution is a highly complex process1 in which divergent1 parallel and convergent modes of development are normally concerned4 ,this complexity greatly increases the difficulty of determining phylogenies1 which would be very much easier could every notable resemblance be at once accepted as proof of relationship4 ,it often renders impossible the classification of some isolated group1 which seems to have several incompatible affinities4 ,it emphasizes the necessity of founding schemes of classification upon the totality of structure and the importance of determining the value of characters1 whether they are primitive or advanced1 divergent1 parallel or convergent1 before attempting to use them in classification4 ,in looking over the field of mammalian evolution1 so far as that is recorded by the fossils1 the general impression received is that the most important process is divergent development1 one line branching out into several4 ,this process became especially vigorous and rapid at times of important change in the character of the environment1 what ,osborn has called 8adaptive radiation40 ,as we have repeatedly observed in the history of particular groups1 e4g4 the rhinoceroses1 horses and camels1 numerous parallel phyla of the same family existed together in certain geological stages1 but as these phyla were traced back in time1 they were found to draw together and display themselves as branches of a single stem4 ,this favours the inference that the mammalian orders1 so far as they are truly natural groups and not arbitrary assemblages1 are each of single1 or monophyletic1 origin1 and that the parallel and convergent modes of development1 while very frequent and important1 are subordinate to divergence4 ,,ii4 ,a second problem is whether development among mammals is always by means of reduction in the number of parts1 or whether that number may not be increased4 ,with this is involved the so-called law of the 8irreversibility of evolution10 according to which organs once lost1 or reduced to a vestigial condition1 are never regained1 or restablished in function4 ,there can be no question that the usual mode of mammalian development is by reduction in the number of parts and the enlargement and elaboration of those which are retained1 as1 for example1 in the reduction of five toes to one in the series of the horses2 but there are cases which require a different explanation4 ,the very numerous teeth of the porpoises and dolphins and of the ,giant ,armadillo are not a primitive feature1 but must have arisen by a process of multiplication4 ,in the very curious ,large-eared ,wolf 7,otocyon7 of ,south ,africa the number of molar teeth #c_/d exceeds that found in any other placental mammal4 ,this feature has been interpreted as a proof of marsupial relationship1 but1 as the creature is a typical dog in all other respects1 such a relationship would involve a degree of convergence in development that is quite inadmissible without the most cogent evidence4 ,until something is learned regarding the descent of ,otocyon1 no positive statement can be made as to the significance of its exceptional dentition1 but much the most likely supposition is that additional teeth have been developed in an otherwise normal canid4 ,however that may be1 the testimony of the fossils is unequivocally to the effect that the usual mode of development among mammals is by a reduction in the number of parts1 accompanied by enlargement and specialization in those which are retained4 ,it is equally clear that the 8law of irreversibility0 holds good in a very large number of cases1 but whether it is always valid is very doubtful4 ,in the ,guinea ,pig1 as in all its family 7,caviid71 there are four toes in the front foot1 three in the hind2 but ,professor ,castle has lately succeeded in producing a race with four toes in the hind foot4 ,to call this a 8monstrosity0 or 8abnormality0 explains nothing2 the fact remains that the four-toed race has been established and no reason can be assigned why the same thing might not happen in nature4 ,if ,dr4 ,matthew's view concerning the origin of the ,american deer from ,leptomeryx 7p4 #dji71 should prove to be well founded1 another example of the same kind would be furnished4 ,in ,leptomeryx of the ,oligocene the upper canine was reduced to minute1 almost vestigial proportions1 while in the ancestral deer1 ,blastomeryx of the lower ,miocene1 it was a large1 scimitar-like tusk4 ,while ,i am unable to accept this derivation of the deer1 it may be true nevertheless and1 if so1 will be a most interesting example of the rehabilitation of a vestigial organ4 ,decision must await the discovery of the intermediate forms4 ,many such cases and instances of the addition of parts may be so far undetected1 but the phylogenetic series1 as we have them before us1 point decidedly to the conclusion that such rehabilitation or new addition is exceptional4 ,,iii4 ,so far as we are able to follow it by the aid of the fossils1 development among the mammals would appear to be a remarkably direct and unswerving process4 ,when any long-lived phylum1 made up of numerous well-preserved members1 is studied1 the observer cannot fail to be impressed by the straightforward course of the evolutionary process1 as though the animals were consciously making for a predetermined goal1 which1 needless to say1 they were not4 ,a minute cusp makes its appearance on a tooth1 enlarges steadily in each succeeding genus1 and ultimately becomes a very important element in the pattern2 and in this series of changes there is no oscillation backward and forward4 ,in the perissodactyls and a few other groups1 the premolars in each family gradually and steadily assumed the size and complexity of molars2 beginning at the hinder end of the series1 these teeth one by one become molariform1 not in irregular and haphazard fashion1 but by perfectly graded stages4 ,the same gradual and direct process was maintained in the oft-recurring reduction of digits among the hoofed animals1 differing for each group according to the symmetry of the foot4 ,in the horses1 for example1 the first digit became vestigial and disappeared1 and then the fifth followed1 leaving a three-toed foot1 in which the median digit was notably the largest and bore most of the weight4 ,throughout the ,oligocene and ,miocene epochs the horses were all tridactyl1 but there was a gradual enlargement of the median digit and dwindling of the laterals1 until these became mere dew-claws1 not touching the ground1 and the weight was carried entirely upon the median one4 ,finally1 the laterals lost their phalanges and were farther reduced to splints1 which is the modern condition4 ,in the same gradual and unswerving manner the higher artiodactyls went through a process of digital reduction from five to two1 and numberless other instances of similar sort might be adduced4 ,on the other hand1 the direction of change long followed may be departed from1 the deviation being due to the introduction of a new factor4 ,in the earliest deer the males were hornless1 but they developed effective weapons of defence by the enlargement of the upper canine teeth into long and sharp1 sabre-like tusks4 ,when antlers appeared1 the work of defence was transferred to them1 and the tusks began to dwindle1 being eventually suppressed in those deer which had large and complex antlers1 though persisting to the present time in the hornless ,musk ,deer and in the small-antlered ,muntjaks1 which can defend themselves with their sharp tusks4 ,it would be inaccurate to say that fluctuations in the size and effectiveness of parts never occurred2 on the contrary1 there is evidence that such fluctuations in details were not infrequent1 and may have been even more common than we suppose4 ,to give one instance1 the very early camels of the upper ,eocene and lower ,oligocene had small canines1 which though not at all functionless or vestigial1 were yet little larger than incisors4 ,though the ancestral camels of the middle and lower ,eocene are not yet definitely known1 there is strong reason to believe that in them1 as in all of their contemporaries among the ungulates1 the canines were enlarged and fang-like4 ,if so1 the canine teeth in the camels underwent decided fluctuations in size1 being first larger1 then smaller and again enlarging4 ,if ,dr4 ,matthew's interesting theory as to the origin of the true felines from primitive sabre-tooth cats 7see p4 #edj7 should be confirmed1 it would furnish a very striking example of fluctuating development4 ,the acceptance of the theory involves the admission of the following changes3 7#a7 ,the upper canine was enlarged and changed into a thin1 recurved1 scimitar-like tusk2 7#b7 the lower canine was much reduced1 becoming little larger than the incisors2 7#c7 the lower jaw developed a flange on each side from its inferior border1 against which the inner side of the upper canine rested1 when the mouth was closed1 and the chin was nearly flat1 meeting the outer surface of the jaw at a right angle4 ,after these peculiarities had been fully established1 the stock divided into two series2 in one1 the machairodonts1 the specialization continued along the same lines1 assuming more and more exaggerated forms1 while in the true cats it was reversed4 ,the upper canine grew shorter and thicker1 the lower canine was very greatly enlarged1 the lower jaw lost its flange1 and its external and anterior surfaces no longer met at a right angle1 but curved gradually into each other4 ,as previously stated1 such a reversal strikes me as improbable and not to be accepted without very much more complete evidence than we now have1 but it is perfectly possible that such evidence may be forthcoming4 ,making the fullest allowance for all such cases of fluctuation1 it remains true that in the great majority of the phyla whose history may be followed in some detail1 development has been remarkably direct and unswerving4 ,plasticity of organization and capacity for differentiation of structure in widely different directions would seem to be limited in the mammals1 especially among the more advanced groups4 ,,iv4 ,a question that has been much debated and is still a centre of controversy deals with continuity and discontinuity in development4 ,in other words1 does evolution proceed by the cumulative effects of minutely graded modifications1 or is it a succession of leaps and sudden changes8 ,the difference is illustrated by many breeds and races of animals and plants under domestication1 the history of which is known4 ,some have arisen from 8sports10 sudden and marked deviations from the parent stock1 which 8breed true0 from the beginning4 ,of this character was the ,ancon breed of sheep1 which was derived from a single short-legged ram that was born of normal parents in #agia and transmitted his peculiarities to his offspring4 ,professor ,castle's race of four-toed ,guinea ,pig originated from one four-toed individual1 which suddenly appeared in a litter of normal ones4 ,other breeds have been formed by the careful and long-continued selection of minute individual variations4 ,which of these methods is the one that has been followed under natural conditions8 or has now one method been used and now another1 according to circumstances8 ,the problem is one that has a profound and far-reaching importance for the whole of evolutionary philosophy1 which largely hinges upon it4 ,unfortunately1 palontology is not well fitted to give a decisive answer to these questions1 for1 however complete the record of any given series may be1 we never can be sure that it actually is so1 and interruptions in the continuity of development might be due either to progress by abrupt changes1 or to a failure to preserve all the gradations4 ,for that reason different observers have put divergent interpretations upon the facts as we have them4 ,the general impression that is made by the study of a well-preserved mammalian phylum is that of continuity1 but a closer analysis reveals numerous small breaks1 and suggests1 so far as the record may be trusted1 that the advance was made by separate steps1 though very short ones4 ,indeed1 it has been objected that so completely recorded a phylum as that of the horses must be illusory1 because there is not perfect continuity between the successive genera1 it being taken for granted that such continuity is the normal mode of development4 ,dr4 ,schlosser1 on the other hand1 is a disbeliever in perfect continuity4 8,i am of the opinion that we must reckon with development per saltum more frequently than is usually done4 ,we have been decidedly spoiled by the phylogenetic series of quiet successive development1 such as we meet with in the ,oligocene and ,miocene of ,north ,america in the titanotheres1 oreodonts1 camels1 etc41 and in the upper ,eocene of ,europe in ,palotherium1 ,paloplotherium1 etc41 as well as from the ,oligocene into the ,pleistocene1 e4g41 in the rhinoceroses1 cervids1 suillines1 amphicyonids4 ,even here we often make for ourselves artificial difficulties by balancing1 with an exaggerated scrupulousness1 the individual forms one against another1 to see whether they really are exactly fitted to fill up any gaps4 ,it is not the lack of suitable intermediate forms which so often renders difficult the establishment of genetic series1 but1 quite on the contrary1 the abundance of the forms at our disposal1 among which we must make a choice4 ,if1 however1 the development of phyla did not take place in the same region and under constant climatic and topographical conditions1 we must necessarily find apparent gaps1 for adaptation to a new environment occasions rapid changes of organization1 so that the immediate descendant will often deviate considerably from its ancestor4 ,but that must not mislead us into denying the connection between such forms40#bb ,better adapted to a solution of this problem than mammals are the fossil shells of ,mollusca1 the development of which may often be traced through a thick series of strata1 each step of modification being represented by innumerable individuals4 ,in very many instances it appears that each species in a series of successive modifications had many contemporary fluctuating variations1 but the change from one species to the next succeeding one was by a small though abrupt mutation4 ,the difference between two successive species may be no greater than that between two contemporary variants of the same species1 but it was a constant and not a fluctuating difference4 ,there is much reason to believe that such is at least a frequent mode of development1 namely1 that from species to species and genus to genus the transition has been by slight and sudden changes4 ,the possibility that such abrupt changes1 however slight1 are illusory and due to small gaps in the record1 must be admitted1 and though this does not seem to be a very likely explanation1 it is given plausibility by the almost perfect continuity between successive species which may sometimes be observed4 ,the extremely important and significant distinction between contemporary1 fluctuating variations and successive1 constant mutations was first drawn by ,waagen1 who says of them3 8,one must therefore distinguish strictly between varieties in space and those in time4 ,to describe the former1 the long-used name #8variety' will suffice1 for the latter1 on the other hand1 ,i would propose1 for the sake of brevity1 a new term1 #8mutation4' ,a species as such1 with reference to its connection with earlier or later forms1 may be conceived and regarded as a mutation4 ,but also in regard to the value of these two concepts1 just established 7variety and mutation71 an entirely different value is displayed on closer consideration4 ,while the former appears extremely vacillating1 of small systematic value1 the latter1 even though in minute characteristics1 is extremely constant and always to be recognized with certainty40#bc ,the same conception was adopted and elaborated by ,neumayr3 8,still other characteristics appear1 which mark mutations as something different from varieties1 especially that1 as a rule1 there is a definite direction of mutation in each series1 the same characters changing in the same sense through a considerable succession of strata40#bd ,whether development was continuous or discontinuous1 there is no reason to suppose that the amount and rate of modification were always constant4 ,on the contrary1 there is strong evidence that at times of great climatic or geographical changes1 or when a region was invaded by a horde of immigrants1 widespread readjustments were accomplished with comparative rapidity4 ,indeed1 such periods of relatively quick changes have long seemed to be implied by the facts of the palontological records4 99 99 99 99 99 ,it is only too clear that the principles as to the modes of mammalian development which can be deduced from the history of the various groups must1 for the most part1 be stated in a cautious and tentative manner1 so as not to give an undue appearance of certainty to preliminary conclusions1 which should be held as subject to revision with the advance of knowledge4 ,much has1 however1 been already learned1 and there is every reason to hope that ,experimental ,zology and ,palontology1 by combining their resources1 will eventually shed full light upon a subject of such exceptional difficulty4 ,,footnotes #a ,memoirs of the ,university of ,california1 ,vol4 ,i1 pp4 #bji-baa4 #b ,voyage of a ,naturalist1 ,amer4 ed41 pp4 #acc-acd4 #c ,j4 ,w4 ,gregory1 ,the ,great ,rift ,valley1 p4 #bfh4 #d ,voyage of a ,naturalist1 ,am4 ed41 #ahia1 p4 #hb4 #e ,d4 ,h4 ,scott1 ,studies in ,fossil ,botany1 ,london1 #aijj1 pp4 #ebd-ebe4 #f ,the names1 ,javan and ,sumatran rhinoceroses1 are somewhat misleading1 since both of these species are also found on the mainland of ,india4 #g ,this plausible and no doubt correct explanation was suggested to me by my colleague1 ,professor ,c4 ,f4 ,brackett4 #h ,flower and ,lydekker1 ,mammals ,living and ,extinct1 p4 #ccb4 #i ,flower and ,lydekker1 op4 cit41 pp4 #cjg-cjh4 #aj ,flower and ,lydekker1 op4 cit41 pp4 #cee and #ceg4 #aa ,the ,woodland ,bison of ,canada is now regarded as a distinct species4 #ab ,darwin1 ,voyage of a ,naturalist1 p4 #agb4 #ac ,f4 ,e4 ,beddard1 ,mammals1 ,london1 #aijb1 pp4 #eej1 #eea4 #ad ,bates1 ,naturalist on the ,amazons1 ,london1 #ahge1 pp4 #cb1 #adj4 #ae ,bates1 ,naturalist on the ,amazons1 ,london1 #ahge1 pp4 #ccb1 #ccc4 #af ,beddard1 op4 cit41 pp4 #eee1 #eef4 #ag ,a4 ,hrdlika1 ,smithsonian ,institution1 ,bureau of ,ethnology1 ,bulletin #cc1 #aijg1 p4 #ih4 #ah ,ibid41 ,bulletin #eb1 #aiab1 pp4 #che1 #chf4 #ai ,k4 von ,zittel1 ,handbuch der ,palaeontologie1 ,bd4 ,,iv1 p4 #acb4 #bj ,reports of the ,princeton ,university ,expeditions to ,patagonia1 ,vol4 ,,iv1 ,pt4 #c4 #ba ,w4 ,k4 ,gregory1 ,the ,orders of ,mammals2 ,bull4 ,amer4 ,mus4 ,nat4 ,history1 ,vol4 ,,xxvii1 p4 #baa4 #bb ,m4 ,schlosser1 ,beitrge zur ,kenntniss der ,oligoznen ,landsugethiere aus dem ,fayum1 ,vienna1 #aiaa1 p4 #afe4 #bc ,w4 ,waagen1 ,die ,formenreihe des ,ammonites subradiatus1 ,benecke's ,geognost4-,palont4 ,beitr41 ,bd4 ,i1 pp4 #ahe-ahf4 #bd ,m4 ,neumayr1 ,die ,stmme des ,thierreiches1 ,bd4 ,i1 p4 #fj4 ,,glossary ,acetabulum1 the deep socket in the hip-bone for the head of the femur4 ,acromion1 the projecting lower end of the spine of the shoulder-blade4 ,alisphenoid canal1 canal in the base of the skull for the external carotid artery4 ,allotheria1 an extinct suborder of ,mesozoic and ,paleocene ,marsupials4 ,amblypoda1 an extinct order of hoofed mammals4 ,anconeal fossa1 a deep pit on the posterior side of the humerus1 near the lower end4 ,anconeal process1 see ,olecranon4 ,ancylopoda1 an extinct suborder of ,perissodactyla4 ,angle1 of the lower jaw1 the postero-inferior corner4 ,angular process1 a hook-like projection from the angle of the lower jaw4 ,anterior nares1 the forward opening of the nasal passage4 ,anthropoidea1 ,monkeys1 ,apes1 ,man2 suborder of ,primates4 ,appendicular skeleton1 bones of the limbs and limb-girdles4 ,araucanian1 ,pliocene of ,argentina1 including the ,catamarca and ,monte ,hermoso4 ,artiodactyl1 see ,artiodactyla4 ,artiodactyla1 ,cattle1 ,deer1 ,camels1 ,pigs1 etc41 etc41 order of hoofed mammals4 ,ascending ramus1 posterior1 vertical portion of the lower jaw4 ,astragalus1 the ankle-bone4 ,astraponotus ,beds1 upper ,eocene or more probably1 lower ,oligocene of ,patagonia4 ,astrapotheria1 an extinct order of hoofed mammals4 ,atlas1 the first vertebra of the neck4 ,auditory bulla1 one of a pair of inflated bony capsules at the base of the skull2 the tympanic bone4 ,auditory meatus1 the entrance to the bulla4 ,axial skeleton1 the skull1 backbone1 ribs and breast-bone4 ,axis1 the second vertebra of the neck4 ,barytheria1 an extinct order of elephant-like mammals4 ,biceps muscle1 the large flexor muscle of the front of the upper arm2 its contraction bends the elbow4 ,bicipital groove1 a groove between the tuberosities of the humerus for the upper tendons of the biceps4 ,brachyodont1 low-crowned teeth1 with early-formed roots4 ,bridger stage1 middle ,eocene of ,n4 ,w4 ,america4 ,bunodont1 teeth composed of conical tubercles4 ,calcaneum1 the heel-bone4 ,cannon-bone1 a compound bone formed by the cossification of two or more long bones of the foot4 ,cape ,fairweather1 marine ,pliocene of ,patagonia4 ,carnassial1 a shearing1 sectorial tooth in a flesh-eater4 ,carnivora1 ,wolves1 ,bears1 ,cats1 etc41 etc42 an order of placental mammals4 ,carnivorous1 flesh-eating1 predaceous4 ,carpal1 one of the elements of the carpus4 ,carpus1 the wrist-bones4 ,casa ,mayor stage1 terrestrial formation of ,patagonia1 probably ,eocene4 ,catamarca1 a ,pliocene formation of ,argentina4 ,caudal vertebr1 those of the tail4 ,central1 a small carpal1 wedged in between the two rows4 ,centrum1 the body of a vertebra4 ,cervical vertebr1 those of the neck4 ,cetacea1 ,whales1 etc42 a cohort of marine mammals4 ,chelodactyla1 suborder of ,perissodactyla4 ,chevron-bones1 ,y-shaped bones attached to the under side of the caudal vertebr4 ,chevrotains1 8,mouse ,deer10 of the suborder ,tragulina4 ,chiroptera1 ,bats1 an order of placental mammals4 ,class1 a group of the fifth order in classification4 ,clavicle1 the collar-bone4 ,cnemial crest1 a massive prominence on the front face of the tibia1 near the upper end4 ,cohort1 division of infraclass1 containing a series of related orders4 ,condylarthra1 an extinct order of hoofed mammals4 ,condyle1 a knob-like1 articular protuberance4 ,convergence1 or ,convergent ,evolution1 similar forms resulting from two or more independent lines of descent4 ,coracoid1 a hook-like bone1 fused with the shoulder-blade in the higher mammals4 ,coronoid process1 a projection in front of the condyle of the lower jaw1 to which the temporal muscle is attached4 ,cotyles1 concavities on the atlas to receive the occipital condyles of the skull4 ,cranium1 the part of the skull above and behind the eyes1 which lodges the brain and higher sense-organs4 ,creodonta1 an extinct suborder of the ,carnivora4 ,cretaceous1 third and last of the ,mesozoic periods4 ,crown1 the exposed part of a tooth4 ,deltoid crest1 a ridge on the anterior face of the humerus for the attachment of the deltoid muscle4 ,dental formula1 an arithmetical expression of the number and kinds of teeth4 ,dermoptera1 ,flying ,lemur1 order of placental mammals4 ,deseado stage1 terrestrial formation of ,patagonia1 probably ,oligocene4 ,didelphia1 lower infraclass of the ,eutheria4 ,digit1 a finger or toe4 ,diprotodonta1 ,kangaroos1 etc41 a suborder of ,marsupials4 ,dorsal vertebr1 those which carry ribs4 ,duplicidentata1 ,hares and ,rabbits1 suborder of ,rodentia4 ,edentata1 ,sloths1 ,anteaters1 etc41 an order of placental mammals4 ,edentates1 see ,edentata4 ,embrithopoda1 an extinct order of elephant-like mammals4 ,embryo1 young animal in early stages of development within the uterus4 ,entelonychia1 extinct suborder of the ,toxodontia4 ,eocene1 second of the five ,tertiary epochs4 ,epicondylar foramen1 perforation of the internal epicondyle for transmission of the ulnar nerve4 ,epicondyle1 a rough prominence on each end of the humeral trochlea4 ,epiphysis1 the ends of the long bones1 which ossify separately and do not coalesce with the shaft until growth ceases4 ,equus ,beds1 see ,sheridan stage4 ,eutheria1 the higher subclass of mammals2 viviparous4 ,family1 group of the third order in classification1 typically containing several genera4 ,fauna1 the totality of animals of a given time or place4 ,femur1 the thigh-bone4 ,fibula1 the external bone of the lower leg4 ,fissipedia1 land-carnivores2 suborder of the ,carnivora4 ,flora1 the totality of plants of a given time or place4 ,ftus1 young animal in the later stages of development within the uterus4 ,foramen1 a perforation in a bone for the passage of a nerve or blood-vessel4 ,foramen magnum1 the opening in the occiput for the passage of the spinal cord to the brain4 ,formation1 a general term for a group of strata1 laid down continuously and under uniform conditions4 ,frontal1 one of a pair of bones which form the anterior part of the cranial roof2 the forehead4 ,genus1 group of the second order in classification1 typically containing several species4 ,glenoid cavity1 7of the squamosal7 the articular surface for the condyle of the lower jaw2 7of the scapula7 the socket for the head of the humerus4 ,hallux1 the first digit of the pes1 or great toe4 ,herbivorous1 plant-eating4 ,homalodotheres1 see ,entelonychia4 ,horizontal ramus1 the tooth-carrying part of the lower jaw4 ,humerus1 the bone of the upper arm4 ,hyoid arch1 a series of bony rods1 attached to the base of the cranium1 for support of the tongue4 ,hyopsodonta1 an extinct suborder of the ,insectivora4 ,hypsodont1 high-crowned teeth1 with late-formed roots4 ,hyracoidea1 ,klipdases1 an order of hoofed mammals4 ,ilium1 the anterior element of the hip-bone4 ,inferior maxillary1 the lower jaw4 ,infraclass1 division of subclass4 ,insectivora1 ,moles1 ,shrews1 etc41 an order of placental mammals4 ,ischium1 the postero-superior element of the hip-bone4 ,john ,day stage1 upper ,oligocene of ,n4 ,w4 ,america4 ,jugal1 the cheek-bone4 ,see ,malar4 ,jurassic1 the second of the ,mesozoic periods4 ,lachrymal1 a small bone on the front edge of the orbit4 ,lachrymal foramen1 a canal for the tear-duct piercing the lachrymal bone4 ,lemuroidea1 ,lemurs1 suborder of the ,primates4 ,lemurs1 see ,lemuroidea4 ,limb-girdles1 the bones which attach the limbs to the body4 ,lipotyphla1 suborder of the ,insectivora4 ,litopterna1 extinct order of hoofed mammals4 ,loricata1 ,armadillos and ,glyptodonts2 the armoured ,edentates4 ,lumbar vertebr1 those of the loins4 ,lunar1 the middle bone in the upper row of the carpus4 ,magnum1 the middle bone in the lower row of the carpus2 supports the third digit or middle finger4 ,malar1 cheek-bone4 ,see ,jugal4 ,malleolar bone1 the lower end of the fibula1 persisting as a separate bone after loss of the shaft4 ,malleolus1 external1 the lower end of the fibula4 ,malleolus1 internal1 process from the lower end of the tibia4 ,mammal1 a warm-blooded vertebrate1 which suckles its young4 ,mandible1 the lower jaw4 ,manubrium1 the anterior segment of the breast-bone4 ,manus1 the hand or fore foot4 ,marsupial1 see ,marsupialia4 ,marsupialia1 ,opossums1 ,kangaroos1 etc41 etc42 only order of the infraclass ,didelphia4 ,marsupium1 the hairy pouch in which the young ,marsupials are carried4 ,masseter muscle1 a muscle of mastication1 attached to the lower jaw and inferior border of the zygomatic arch4 ,mastoid1 that part of the periotic bone which is exposed on the surface of the skull4 ,mastoid process1 a spine-like outgrowth of the mastoid4 ,maxillary1 the upper jaw-bone4 ,medullary cavity1 the marrow cavity of a long bone4 ,mesozoic1 the middle era of geological time4 ,metacarpal1 a member of the metacarpus4 ,metacarpus1 the long bones of the manus1 or fore foot4 ,metapodial1 a metacarpal or metatarsal4 ,metatarsal1 a member of the metatarsus4 ,metatarsus1 the long bones of the pes1 or hind foot4 ,miocene1 the fourth of the ,tertiary epochs4 ,monodelphia1 placental mammals2 the higher infraclass of the ,eutheria4 ,monophyletic1 derived from a single line of ancestry4 ,monotremata1 ,duck-billed ,mole and ,spiny ,anteaters2 the only existing order of the ,prototheria4 ,monte ,hermoso stage1 upper ,pliocene of ,argentina4 ,mouse ,deer1 chevrotains2 suborder ,tragulina4 ,mystacoceti1 ,whalebone ,whales2 order of the ,cetacea4 ,nasal1 one of a pair of bones1 forming the roof of the nasal passage4 ,navicular1 central bone of the tarsus4 ,neural arch1 the bony arch of a vertebra4 ,neural canal1 the cavity in the arch1 lodging the spinal cord4 ,neural spine1 or spinous process1 the projection arising from the summit of the neural arch4 ,notostylops ,beds1 see ,casa ,mayor stage4 ,occipital condyles1 a pair of knob-like protuberances from the occiput for articulation with the first vertebra4 ,occipital crest1 an elevated bony ridge around the margin of the occiput4 ,occiput1 the posterior surface of the skull4 ,odontoceti1 ,toothed ,whales2 order of ,cetacea4 ,odontoid process1 a peg-like projection from the body of the second vertebra1 which fits into the ring of the first4 ,olecranon1 the heavy projection from the upper end of the ulna1 forming the point of the elbow4 ,oligocene1 the third of the ,tertiary epochs4 ,opposable1 used of the thumb and great toe1 when they can be opposed to the other digits4 ,orbit1 the bony eye-socket4 ,order1 a group of the fourth rank in classification1 typically including many families4 ,oviparous1 egg-laying4 ,palate1 hard1 the bony roof of the mouth4 ,palatine1 one of a pair of bones which form the hinder part of the hard palate4 ,palatine process1 a shelf-like projection of the maxillary1 which forms most of the hard palate on each side4 ,paleocene1 the oldest of the five ,tertiary epochs4 ,palmate1 form of antler in which the tines are fused into large plates4 ,pampean1 ,pleistocene1 perhaps including the uppermost ,pliocene1 of ,argentina4 ,parallelism1 or ,parallel ,evolution1 similar development of related1 but separate series4 ,paran stage1 lower ,pliocene 7or perhaps upper ,miocene7 of ,argentina4 ,parietal1 one of a pair of large1 vaulted bones1 which form most of the sides and roof of the cranium4 ,paroccipital process1 a bony projection from the infero-external angle of the occiput4 ,patagonian stage1 marine lower ,miocene of ,patagonia4 ,patella1 the knee-cap4 ,pecora1 true ,ruminants1 suborder of ,artiodactyla4 ,pelvic girdle1 see ,pelvis4 ,pelvis1 the hip-bones4 ,periotic1 a small1 dense bone1 which lodges the internal labyrinth of the ear4 ,pes1 the hind foot4 ,petrosal1 see ,periotic4 ,phalanx1 one of the joints of the fingers or toes4 ,pholidota1 ,pangolins or ,scaly ,anteaters2 order of placental mammals4 ,phylum1 a genetic series of ancestors and descendants within a family4 ,pilosa1 ,sloths1 ,anteaters1 etc42 suborder of ,edentata4 ,pinnipedia1 ,marine ,carnivores2 suborder of ,carnivora4 ,pisiform1 an accessory bone attached to the postero-external angle of the carpus4 ,placenta1 a temporary structure connecting mother and ftus1 by means of which the ftus is nourished in the womb4 ,placental1 having a placenta2 the ,monodelphia4 ,pleistocene1 the older of the two ,quaternary epochs4 ,pliocene1 the fifth and last of the ,tertiary epochs4 ,pollex1 the first digit of the manus1 or thumb4 ,polyphyletic1 derived from two or more distinct lines of ancestry4 ,polyprotodonta1 ,opossums1 etc42 suborder of ,marsupials4 ,posterior nares1 the hinder opening of the nasal passage4 ,postglenoid process1 a bony ridge behind the glenoid cavity of the squamosal to prevent backward dislocation of the jaw4 ,postorbital process1 a bony projection from the frontal or jugal1 bounding the eye-socket behind4 ,premaxillary1 the anterior bone of the upper jaw1 carrying the incisor teeth4 ,primates1 ,lemurs1 ,monkeys1 ,apes and ,man2 cohort and order of placental mammals4 ,proboscidea1 ,elephants1 etc42 order of hoofed mammals4 ,process1 a distinct prominence or projection of bone for the attachment of muscle or ligament4 ,proglires1 an extinct suborder of the ,insectivora4 ,prototheria1 most primitive subclass of mammals2 oviparous4 ,pubis1 the postero-inferior element of the hip-bone4 ,pyramidal1 the external bone in the upper row of the carpus4 ,pyrotheria1 an extinct suborder of ,toxodontia4 ,pyrotherium ,beds1 see ,deseado stage4 ,radius1 the internal bone of the fore-arm4 ,rodent1 see ,rodentia4 ,rodentia1 ,gnawers2 order of placental mammals4 ,rotular groove1 a broad1 shallow groove on the anterior face of the femur1 near the lower end1 in which the knee-cap glides4 ,round ligament1 the ligament between the head of the femur and a pit in the acetabulum of the hip-bone4 ,sacral vertebr1 those of the sacrum4 ,sacrum1 a bony mass of fused vertebr1 for the support of the hip-bones4 ,sagittal crest1 a ridge of bone in the median line of the cranial roof1 running forward from the occipital crest4 ,scaphoid1 the inner bone in the upper row of the carpus4 ,scapho-lunar1 a compound bone made up of the coalesced scaphoid1 lunar and central4 ,scapula1 the shoulder-blade4 ,section1 primary division of a suborder4 ,sectorial1 a carnassial or shearing tooth of a flesh-eater4 ,selenodont1 teeth composed of crescent-shaped cusps4 ,shaft1 the body of a long bone1 comprising most of its length4 ,sheridan stage1 older ,pleistocene of the ,great ,plains4 ,shoulder-girdle1 the bones to which the fore limb is attached4 ,simplicidentata1 ,squirrels1 ,rats1 ,porcupines1 etc41 etc42 suborder of ,rodentia4 ,sinus1 an air-cavity in one of the skull-bones4 ,sirenia1 ,sea ,cows and ,dugong2 order of marine mammals4 ,species1 the unit group in classification1 made up of individuals which are most closely similar4 ,spine1 7of the scapula7 a bony ridge on the outside of the shoulder-blade2 7of the tibia7 a single or double prominence from the upper end of the shin-bone2 7of a vertebra7 the neural spine4 ,squamosal1 a bone forming the posterior side-wall of the cranium4 ,sternal ribs1 the inferior segments of the ribs1 which articulate with the breast-bone4 ,sternum1 the breast-bone4 ,stratum1 a layer of bedded rock4 ,subclass1 primary division of class4 ,subfamily1 a group of related genera within the family4 ,subgenus1 a group of related species within the genus4 ,suborder1 primary division of order4 ,subspecies1 a definite subdivision of a species4 ,suina1 swine-like animals2 suborder of ,artiodactyla4 ,superfamily1 a group of related families4 ,superorder1 a group of related orders4 ,supinator ridge1 a crest on the outer side1 near the lower end of the humerus1 for attachment of the supinator muscle4 ,symphysis1 the line of junction of the two halves of the lower jaw4 ,synonym1 a name improperly given to a genus or species already named4 ,tniodontia1 an extinct order of clawed mammals4 ,tarsal1 an element of the tarsus4 ,tarsus1 the bones of the ankle-joint4 ,temporal muscle1 a muscle of mastication attached to the side of the cranium and the coronoid process of the lower jaw4 ,tertiary1 the more ancient of the two ,cenozoic periods4 ,thoracic vertebr1 see ,dorsal4 ,thorax1 the bony frame-work of the chest4 ,tibia1 the shin-bone1 internal bone of the lower leg4 ,tillodontia1 an extinct order of clawed mammals4 ,toxodonta1 an extinct suborder of the ,toxodontia4 ,toxodontia1 an extinct order of hoofed mammals4 ,toxodonts1 see ,toxodonta4 ,tragulina1 8,mouse ,deer02 suborder of ,artiodactyla4 ,transverse processes1 projections from the sides of a vertebra4 ,trapezium1 internal bone in the lower row of the carpus2 supports the first digit1 or thumb4 ,trapezoid1 second bone in the lower row of the carpus2 supports the second digit1 or index finger4 ,triassic1 first of the three ,mesozoic periods4 ,triconodonta1 an extinct suborder of ,mesozoic ,marsupials4 ,trituberculata1 an extinct order of ,mesozoic mammals4 ,trochanter1 a projection from the femur4 ,trochanter1 third1 a hook-like process on the outer side of the shaft of the femur1 near the middle of its length4 ,trochlea1 the pulley-shaped lower end of the humerus for articulation with the fore-arm bones4 ,trunk vertebr1 those of the body1 the dorsals and lumbars4 ,tubercle1 an articular projection on a rib1 connecting with the transverse process of a dorsal vertebra4 ,tuberosities 7of the humerus71 heavy projections from the upper end of the bone1 in front of the head4 ,tubulidentata1 the ,aard ,vark2 an order of placental mammals4 ,tylopoda1 ,camels and ,llamas2 suborder of ,artiodactyla4 ,tympanic1 a bone forming the support of the ear-drum and usually inflated into a hollow capsule4 ,typotheres1 see ,typotheria4 ,typotheria1 an extinct suborder of the ,toxodontia4 ,ulna1 the external bone of the fore-arm4 ,unciform1 the external bone in the lower row of the carpus2 supports the fourth and fifth digits1 or ring and little fingers4 ,unconformity1 the relation between two groups of strata1 one of which was deposited upon the worn surface or upturned edges of the other4 ,ungual phalanx1 the terminal joint of a digit1 which supports the claw1 nail or hoof4 ,unguiculata1 clawed mammals2 cohort of ,monodelphia4 ,ungulata1 hoofed mammals2 cohort of ,monodelphia4 ,ungulates1 see ,ungulata4 ,uterus1 the womb4 ,vagina1 the genital canal of the female4 ,variety1 a more or less constant group within a species4 ,vertebra1 a joint of the backbone4 ,vertebral column1 the backbone4 ,viviparous1 producing living young4 ,zeuglodontia1 an extinct order of ,cetacea4 ,zygapophyses1 the projecting processes1 by means of which successive vertebr are articulated together4 ,zygomatic arch1 a bony bridge from the eye-socket to the hinder part of the cranium4 ,,index ,n4 ,b4--,the most important references are in heavy-faced type2 technical names of genera and species are italicized1 though most of the specific names are omitted as unnecessary4 ,extinct groups are indicated by a dagger 774 ,aard ,vark1 #fj ,abderites1 #fbg1 #fda 7jaw fig47 ,achnodon1 #bgc1 #cfa1 #cfi 7skull fig471 #cgj ,achnodonts1 ,bridger1 #cfi2 ,uinta1 #cfi2 ,wasatch1 #cgj ,aclodid1 #dgg ,adaptive radiation1 #fee ,adinotherium1 #dfb1 #dgc1 #dgd 7restoration7 ,adpithecus1 #dfb lurocyon1 #eag1 #eea lurodon1 #eag1 #ebg lurus1 #edf ,africa1 #ahd1 #bde1 #cbh1 #ccb1 #dag1 #dai1 #dba1 #dbb1 #dbf1 #ddb1 #deh1 #dha1 #eea1 #egi1 #fdb1 #fef2 elephants of1 #ach2 mammals of1 #ade2 zology of1 #adf ,,agassiz1 ,l41 #abi ,age1 geological1 #ae ,agouti1 #ahe 7fig47 ,agouti1 #ahc 7fig471 #ahe ,agoutis1 ,pleistocene1 #bah ,agriochrid1 #bdg1 #bej1 #cfa1 #chc1 #dhd1 #feb2 ,eocene1 #chc2 ,john ,day1 #bej1 #chc2 ,oligocene1 #chc2 ,uinta1 #bfg1 #che2 ,white ,river1 #bfh1 #chc ,agriochrids1 see ,agriochrid ,agriochrus1 #beb 7restoration71 #cfa1 #chc 7skull fig471 #chd 7restoration71 #che 7manus fig47 ,alachua stage1 #abg1 #bbe ,alaska1 #ajc1 #ajf1 #aig1 #aii1 #bjb1 #bjc1 #ccb1 #dah1 #dai1 #dbj1 #dbg1 #dcc2 ,mammoth in1 #dj2 ,miocene of1 #aah2 ,oligocene of1 #aac2 ,pleistocene glaciation in1 #aca2 volcanoes1 #acc2 ,pliocene of1 #abe ,albertogaudrya1 #eji1 #eab ,alce1 #fe1 #aea1 #aef 7fig471 #bjb1 #bjh1 #cfb1 #daa1 #dab ,,allen1 ,j4 ,a41 #ada1 #afa ,alligators1 #ajb ,allothere1 ,paleocene41 #fdb 7skull fig47 ,allotheria1 #ei1 #fbg1 #fdb ,alouatta1 #egh1 #ehe ,alps1 ,arctic animals and plants of1 #aic2 ,eocene1 #ajd ,alticamelus1 #bbd1 #cfb1 #chh1 #cia2 restoration1 #bcf ,amazon1 #ehe2 as barrier to species1 #acg ,amblypoda1 #fj1 #ddc1 #ejh2 ,bridger1 #bfi1 #dde2 ,eocene1 #ddc2 ,puerco1 #bhf1 #ded2 ,torrejon1 #bhe1 #dec2 ,wasatch1 #bgg1 #deb2 ,wind ,river1 #bgd1 #dej1 #deb ,amblytatus1 #eib ,,ameghino1 ,f41 #bbh1 #bfc1 #dfg1 #dga1 #dgf1 #dif1 #dig1 #fac ,america1 connections of ,north and ,south1 #abc ,american ,mastodon1 #aif2 restoration1 #aie ,americas1 marsupials of1 #ach ,amherst expedition1 #dhg ,amphibia1 #ee2 as ancestral to mammals1 #fdc ,amphicyon1 #eag1 #ebd1 #ebe1 #ecj ,amphicyons1 #eeh ,amphidolops1 #fbg ,amphiproviverra1 #fbg1 #fcg2 skull fig41 #fcg ,amynodon1 #bgb1 #bia1 #cdj1 #cdh1 #cdi ,amynodontin1 #bia1 #cdj1 #cda1 #cdf1 #cej1 #cea1 #cec2 ,bridger1 #bgb1 #cej2 ,oligocene1 #cci2 ,uinta1 #bff1 #cdh2 ,white ,river1 #bee1 #cdf4 ,amynodonts1 see ,amynodontin ,anacodon1 #bgg1 #eed1 #efa ,analcitherium1 #eib ,anaptomorphid1 #egh1 #ehc ,anaptomorphus1 #bha1 #egh1 #eha2 head restored1 #eha ,anchitherium1 #bij1 #bii ,ancon sheep1 #ffj ,ancylopoda1 #fj1 #bia1 #cec2 ,bridger1 #ceg2 ,miocene1 #bch1 #cee2 ,pliocene1 #bbd1 #cee ,andes1 #agh1 #agi1 #ahj1 #ahe1 #ahi1 #baa1 #bac1 #cbb1 #edh2 ,eocene1 #aab2 ,miocene1 #abd2 ,pleist4 glaciation1 #acc1 #acd2 ,plioc4 #abh1 #abi ,,andrews1 ,c4 ,w41 #dbb1 #dce ,antarctic continent1 #ajc1 #abc1 #fch ,ant-,bear1 #ia1 #ahg1 #ahh 7fig471 #bjf1 #eia1 #cee1 #fjj1 #fja1 #fae ,anteater1 ,collared1 #ahg1 #ahh 7fig472 ,lesser1 #eia2 tree1 #eia2 ,two-toed1 #ahh ,anteaters1 #fj1 #ge1 #id1 #ahg1 #ahi1 #eia1 #eic1 #eif2 ,pleistocene1 #bah1 #eif2 ,santa ,cruz1 #bde1 #eif2 scaly1 #fj1 #cec2 spiny1 #eg1 #ei ,antelope1 #bjb2 bones of1 #ce2 ,mioc4 restored1 #bcg2 ,prong-horned1 #e1 #afb 7fig47 ,antelopes1 #ed1 #fj1 #bbb1 #cab1 #cfb1 #dji1 #daf1 #dah2 flat-horned1 #dag2 goat-horned1 #dag2 ,miocene1 #bce1 #dag2 ,old ,world1 #bjb2 ,pleistocene1 #bjb2 ,pliocene1 #bbd2 ,s4 ,amer41 #bac1 #bae1 #bba1 #dah1 #dff2 strepsicerine1 #bbe1 #dag2 ,tertiary1 #dai2 twisted-horned1 #dag ,anthracotheres1 see ,anthracotheriid ,anthracotheriid1 #bei1 #bff1 #cfa1 #cgj1 #cha1 #chd1 #chf ,anthracotherium1 #bei1 #cfa1 #cga ,anthropoidea1 #fj1 #egh1 #egi1 #ehj1 #ehb ,anthropoids1 see ,anthropoidea ,antigua1 #acd ,antilles1 ,eocene1 #aab2 ,miocene1 #abc2 ,oligocene1 #aag2 ,pliocene1 #abh ,antillia1 #aab2 ,oligocene1 #aag ,antilocapra1 #afb 7fig471 #bjb1 #bbe1 #cfb1 #daf1 #dag ,antilocaprid1 #cfb1 #daf ,antilopid1 #daf ,antler1 #daa ,antwerp1 #cg ,apar1 #eib ,apes1 #fj1 #egg1 #egh1 #ehb1 #ehc2 night1 #ehe ,aphelops1 #bia ,aplodontia1 #aec1 #bcc 7see ,sewellel7 ,aplodontiid1 #bdi ,appalachian ,mts41 #aja1 #aej1 #aec ,aquatic habits1 #b ,araucanian stage1 #abh ,arboreal animals1 #b1 #gg1 #hd ,archan period1 #ae ,archlurus1 #bdi1 #eag1 #eda1 #edc ,archohyracid1 #dfb ,archohyrax1 #dfb ,archopithecid1 #dfb1 #dgg ,archotherium1 #bei1 #cfa1 #cfg2 manus fig41 #cfg2 restoration1 #beb1 #bfj2 skull fig41 #cfg2 teeth fig41 #cfh ,arctic1 archipelago1 #abe2 islands1 #baj2 fauna in ,pleisto41 #abh2 mammals1 #aji2 regions1 #abh2 ,cretac4 climate of1 #bf2 ,sea1 #ajf2 shells1 ,pleisto41 #bg2 species1 distribution of1 #ada2 zone1 #adg 7map71 #adh ,arctocyonid1 #eed1 #eeg1 #efa1 #ege2 ,torrejon1 #bhe2 ,wasatch1 #efa ,arctotherium1 #baa1 #eag1 #edi1 #eec2 head restor41 #edi ,argentina1 #ahj1 #ahe1 #baa1 #bac1 #bae1 #bah1 #bai1 #bde1 #cbd1 #cia1 #dah1 #dcf1 #dfc1 #dff1 #eca1 #ehf1 #eif1 #eig2 drought in1 #cc2 plains of1 #acc2 ,pliocene of1 #bj1 #abh2 spread of horses and cattle in1 #adb ,argyrohippus1 #dgf ,arid province1 #afd ,aridity1 evidences of1 #bd ,arikaree age1 or stage1 #ag1 #abj1 #bce1 #bei1 #cef ,armadillo1 #e1 #afb1 #eia2 #f-;,banded1 #ahi 7fig471 #eib2 #g-;,banded1 #eib2 #i-;,banded1 #aij 7fig471 #eib1 #eic2 #aa-;,banded1 #eib2 ,bridger1 #bfh1 #faf2 ,giant1 #aij1 #eib1 #fab1 #fef2 ,pygmy1 #eib2 restoration of ,santa ,cruz1 #bdc1 #dhj ,armadillos1 #fj1 #ig1 #ada1 #ahe1 #ahi1 #eib1 #eic1 #eid1 #eie1 #faj1 #fbc1 #fbd1 #fbe2 ,araucanian1 #bbf2 ,casa ,mayor1 #bhb1 #eie2 ,deseado1 #bfb1 #eie1 #faf2 ,paran1 #bbh2 ,pleistocene1 #bah1 #eif1 #fab1 #fac2 ,santa ,cruz1 #bde1 #eif1 #fab4 7,see also ,dasypoda and ,dasypodid7 ,artiodactyl1 primitive1 restoration1 #beb ,artiodactyla1 #ed1 #ee1 #fj1 #fi1 #bdg1 #bhd1 #caj1 #cee1 #ceh1 #djb1 #dei1 #dfj1 #dia1 #ejg1 #ead2 ,araucanian1 #bbf1 #bbg2 ,blanco1 #bbb2 ,bridger1 #bgc2 classification1 #cfa2 ,john ,day1 #bej2 ,miocene1 #bca1 #bce1 #bci2 ,neotropical1 #agf2 ,north ,american1 #agf2 ,old ,world1 #agf1 #cfb2 ,pleisto4 ,n4 ,amer41 #bja2 ,s4 ,amer41 #bac2 ,pliocene1 #bbd2 ,primitiva1 #fj1 #cfa1 #cgj2 ,uinta1 #bff2 ,wasatch1 #bha2 ,white ,river1 #bee1 #beg2 ,wind ,river1 #bge ,ash1 volcanic1 #bi ,asia1 #ajf1 #bci1 #bed1 #beh1 #bhj1 #cag1 #cba1 #cbh1 #ccb1 #ceb1 #cee1 #cfi1 #chf1 #cij1 #djh1 #dac1 #dad1 #dag1 #dah1 #dai1 #dbb1 #dbf1 #edf1 #eej1 #eeb1 #egi1 #fdd2 circumpolar area1 #adh2 elephants of1 #ach2 hyracoids of1 #ach2 ,minor1 #deh2 ,pleisto4 glaciation of1 #acj2 zology of1 #adf ,asmodeus1 #dfb ,asphalt1 #ca ,ass1 #eb ,asses1 #bac1 #bib1 #cjh ,asterostemma1 #eib1 #fbc ,astragalus1 #hh ,astraponotus1 #eji1 #eab2 ,beds1 #bj1 #bha1 #bhb1 #dgf1 #dgi1 #dhg ,astrapothere1 ,santa ,cruz1 restoration of head1 #bdc ,astrapotheres1 see ,astrapotheria ,astrapotheria1 #fj1 #dhi1 #ejh1 #ead2 of ,astraponotus ,beds1 #bhb2 ,casa ,mayor1 #bhc1 #eab2 ,deseado1 #bfd1 #eab2 ,patagonian1 #eab2 ,santa ,cruz1 #bdg1 #ejh ,astrapothericulus1 #eji1 #eab ,astrapotheriid1 #eji ,astrapotherium1 #bdc 7restor4 of head71 #eji1 #eaj 7restor4 of head7 ,ateles1 #egh1 #ehd ,atlantic coast1 ,eocene1 #ajd1 #aaa1 #aag2 ,miocene1 #aag1 #abj2 ,oligocene1 #aac1 #aaf2 ,paleocene1 #aja2 ,pliocene1 #abe2 ,tertiary mammals of1 #cfi ,atlantic ,ocean1 #ajf1 #aji2 connection with ,pacific1 #ajd ,atlas1 #gj 7fig47 ,auditory bulla1 #ff ,australia1 #ad1 #ba1 #eg1 #eh1 #ach1 #adj1 #cjg1 #cdj1 #dbf1 #dfa1 #ebj1 #eej1 #fcd2 marsupials of1 #fbf2 ,miocene1 #abc2 ,permian glaciation1 #be2 ,pleistocene1 #fcb1 #fcd2 rabbits introduced1 #adb2 zological peculiarity of1 #ade ,australian region1 #fdj ,axis1 #ga 7fig47 ,axis1 #df1 #dab ,,azara1 #cd ,baboons1 #egg1 #ehb ,bad ,lands1 #ajg 7fig47 ,badger1 #aec1 #afb1 #afc1 #afh 7fig471 #eag ,badgers1 #agd1 #bac1 #eah1 #eej1 #eea1 #eeb2 ,pleistocene1 #bjc1 #bjd1 #bje ,bahia ,blanca1 #abi ,bandicoots1 #fbf ,barriers to spread of mammals1 #aci ,barytheria1 #fj ,basal ,eocene1 #ii ,bassariscus1 #eag1 #edf1 #edg ,bat1 #hi ,,bates1 ,h4 ,w41 #ehe ,bathyopsis1 #bge1 #ddc1 #dej1 #dea1 #dee ,bats1 #ei2 absence from ,amer4 ,tertiary1 #ci2 in ,european ,tertiary1 #ci2 ,west ,indian1 #aia ,bear1 ,alaska ,brown1 #aef 7fig472 ,african1 #edh2 ,black1 #ij 7pes fig471 #edh 7teeth fig472 ,pampean1 #fbb2 ,polar1 #adh 7fig471 #edh2 ,short-faced1 #edi 7restor4 of head72 ,south ,american1 #eeb2 ,spectacled1 #agb 7fig471 #agf1 #eag1 #edh ,bear-dog1 #bbb2 ,miocene1 #ebe 7restoration72 primitive1 #ebc 7skull fig47 ,bear-dogs1 #ebc1 #ebd1 #ecj1 #eed1 #eeh2 ,john ,day1 #bdi2 ,oligocene1 #ebf2 ,pliocene1 #bbb2 ,pleistocene1 #ebd ,bears1 #d1 #ei1 #ij1 #aeb1 #afc1 #eag1 #eah1 #eai1 #edh1 #eec1 #eed2 ,old ,world1 #bjd2 ,old ,world origin of1 #eah1 #edi2 ,paran1 #bbg2 ,pleistocene1 #bjc1 #bjd1 #edi2 ,pliocene1 #bbc2 polar1 #ada2 ,short-faced1 #baj1 #baa1 #eag1 #edi2 true1 #baa1 #ebg1 #edi4 7,see also ,ursid7 ,beast1 #a ,beasts of prey1 #ei1 #ib ,beaver1 #b1 #dd1 #aeg 7fig472 dentition1 #if 7fig472 ,giant1 #aie 7restoration71 #bje1 #caa1 #bbb ,beaver ,creek1 ,wyo41 #ab 7fig47 ,beavers1 #fj1 #ie1 #aec1 #ahb2 ,john ,day1 #bdi2 ,miocene1 #bch2 ,pliocene1 #bbb2 ,white ,river1 #bed ,,beddard1 ,f4 ,e41 #ehj1 #ehg ,bedded rocks1 #f ,bering1 ,sea1 #ajj1 #aja2 ,strait1 #aig1 #ehh2 opening and closing of1 #bc2 ,pliocene1 #abe ,,berridge1 ,w4 ,l41 #afj1 #aga1 #agd1 #age1 #aha1 #ahc1 #ahd1 #ahe1 #ahi1 #cbj1 #ehd1 #fcc ,bicuspids1 #ic ,big ,horn ,basin1 #ajg1 #ajh1 #aji ,bighorn1 #dai ,binomial system of nomenclature1 #db ,biogenetic law1 #fdh ,birds1 #fee2 distribution of1 #ada2 migrations of1 #adc2 ,santa ,cruz1 #bdd ,bison1 #d1 #aeb1 #afb1 #ceh2 ,american1 #aed 7fig472 entombment of1 #cf2 ,european1 #aeb1 #aed 7fig472 ,wood1 #afb1 #dai ,bison1 #bjb1 #cfb1 #dbj2 ,b4 bison1 #aeb1 #aed 7fig471 #dai2 ,b4 bonasus1 #aeb1 #aed 7fig471 #dbj2 ,b4 crassicornis1 #bjc1 #dbj2 ,b4 latifrons1 #bjc1 #dbj2 ,b4 occidentalis1 #ehi ,bisons1 #dji1 #daf1 #dah1 #dai ,blanco age and stage1 #ag1 #abg1 #bba1 #chh1 #dac1 #eea ,blarina1 #afc1 #agc ,blastoceros1 #ahj 7fig47 ,blastomeryx1 #bbd1 #bda1 #cfb1 #dad 7restoration71 #feg ,boar1 ,wild1 #de 7fig4 of sow and young71 #df1 #cfc ,bogs1 burial of mammals in1 #cc ,bolivia1 #agh1 #ahd1 #bae1 #bbe1 #dcf2 ,pleistocene1 #bj1 #baa2 ,pliocene1 #abi ,bones1 gnawed1 #cf2 ,pleistocene1 #dj2 preservation of1 #cf2 ,tertiary1 #dj ,bochrus1 #cfa1 #cfg ,boreal1 fauna1 #agh2 region1 #aej2 subregion1 #aej2 zone1 #adg1 #adh 7map71 #afb1 #afd1 #eea1 #ehh ,borhyna1 #bdd1 #did 7restoration71 #fbg1 #fce1 #fcg 7skull fig47 ,borneo1 #acg1 #cbg ,borophagus1 #eag1 #ebd1 #ecj ,bos1 #gj ,bothriodon1 #beb 7restoration71 #bei1 #cfa1 #cgj1 #cga 7restoration7 ,bovid1 #cfb1 #dah ,bow-,tooth1 #dfc ,brachyodont teeth1 #ie ,brachypsalis1 #eag ,,brackett1 ,c4 ,f41 #cfh ,bradypus1 #ahf 7fig471 #ahg1 #eia ,brain-casts1 fossil1 #da ,brazil1 #aah1 #aha1 #aij1 #bja1 #bac1 #bae1 #bah1 #bai1 #bba1 #bde1 #cbd1 #cia1 #dcf1 #ebg1 #ecj1 #eeb2 caverns of1 #ai1 #cj1 #acc1 #baa1 #bah1 #bba1 #ehf1 #eif2 ,miocene1 #eif2 ,pleistocene1 #bj ,brazilian subregion1 #afd1 #agj 7map71 #aia ,bridger age and stage1 #ag1 #cj1 #aji1 #aaj1 #cdj1 #chj1 #chf1 #efh2 restorations of mammals1 #bga ,british ,columbia1 ,miocene1 #aah2 ,oligocene1 #aac2 ,pleistocene glaciation1 #aca2 ,pliocene1 #abe ,brocket1 ,wood1 #aha 7fig47 ,brockets1 #aha ,,brown1 ,b41 #baj ,brown-tailed ,moth1 #adc ,budorcas1 #dah ,buffalo1 #cf1 #aeb ,buffaloes1 #dji1 #daf ,bulgaria1 #caf ,bunlurus1 #eag1 #eea ,bunodont teeth1 #cfj ,bunomeryx1 #cfa ,buno-selenodont teeth1 #cga ,buried valleys1 #acb ,,burmeister1 ,h41 #dif1 #dig ,burrowers1 #de1 #gi ,burrowing mammals1 #gg ,bush-,dog1 #agd1 #bab1 #ebg1 #ecj1 #eeb ,cabassous1 #eib1 #fad1 #faf ,cacajao1 #egh1 #ehe ,cacomistle1 #afb1 #eag1 #edf ,cnolestes1 #eh1 #aij1 #bhd1 #fbf1 #fdj 7skull fig471 #fda1 #fdb ,cnolestid1 #fbg ,cnopus1 #bch1 #beb 7restoration71 #bef 7do471 #bia1 #ccc1 #ccf 7molar and skull fig471 #cci 7front teeth fig471 #cdb1 #cea ,calamodon1 #bgd ,calcaneum1 #hh ,california1 ,eocene1 #ajd1 #aaa2 marine ,pleisto41 #acb2 ,mesozoic1 #bc2 ,miocene1 #aah1 #aba1 #abg2 ,pliocene1 #abe ,callithrix1 #bah ,caluromys1 #fca ,cambrian period1 #ae2 glaciation in1 #be ,camel1 #dh1 #ed1 #fj1 #gj1 #gi1 #ceh1 #dij2 distribution1 #ach2 family1 #agh2 ,miocene1 #bcb 7restoration72 tribe1 #ac2 ,true1 #agh2 ,white ,river1 #beb 7restor47 ,camelid1 #cfb1 #chf2 distribution1 #ach ,camel-like animals1 #chf ,camels1 #ef1 #ha1 #hd1 #hg1 #ij1 #beg1 #beh1 #cab1 #cfb1 #cgc1 #chf1 #dba1 #dfa1 #fea1 #fee2 ,bridger1 #bgc1 #cih2 browsing1 #chh1 #cic2 ,eocene1 #cig1 #cih1 #djb1 #fei2 grazing1 #cic2 ,john ,day1 #bej1 #cid2 ,miocene1 #bca1 #bcb1 #bce1 #bda1 #cia2 ,old ,world1 #bca2 ,oligocene1 #cid1 #djb1 #fei2 phyla of1 #fej2 ,pleistocene1 #aif1 #bjb2 ,pliocene1 #bbd1 #chh2 true1 #ac1 #chf1 #chg1 #cij1 #cia2 ,uinta1 #bfg1 #cig2 ,white ,river1 #beg1 #cid ,camelus1 #gj1 #ach1 #cfb1 #chg ,canada1 #beg1 #ceg1 #efe2 ,eocene climate1 #aaa2 ,paleocene1 #ajb2 ,white ,river1 #aac2 zology1 #adf ,canadian fauna1 #aea2 subregion1 #adg1 #aej ,canid1 #agc1 #bbc1 #eag1 #eah1 #ebj2 fox-like1 #ebi 7,see also ,dogs7 ,canimartes1 #eag ,canine teeth1 #ic ,canis1 #aeb1 #eag1 #ebb1 #ebi2 ,c4 dirus1 restor41 frontispiece1 #bjd1 #eba2 ,c4 indianensis1 #bjd2 ,c4 latrans1 #afb1 #afe 7fig471 #fcb2 ,c4 nubilis1 #aei 7fig472 ,c4 occidentalis1 #fb 7skull fig471 #fd 7skull fig471 #afb4 7,see ,wolves7 ,cannon-bone1 #hd1 #ia 7fig471 #daj 7fig47 ,cape ,fairweather stage1 #abh ,capromeryx1 #cfb1 #dag ,capromys1 #ahd ,capybara1 #bje4 7,see also ,carpincho and ,water ,hog7 ,capybaras1 ,pleistocene1 #bah ,carboniferous period1 #ae ,caribbean1 region1 ,miocene1 #abc2 ,sea1 ,oligocene1 #aac ,caribou1 #d1 #aha1 #bjb1 #bjg1 #bjh1 #baj1 #dab1 #dac2 ,barren-ground1 #adh2 ,pleistocene1 #bg1 #dac2 ,woodland1 #aeb1 #aeg 7fig47 ,carnivora1 #dc1 #ei1 #hc1 #ij1 #bdd1 #bfh1 #bhb1 #bhd1 #bhe1 #dei1 #eaf1 #fcd2 ,araucanian1 #bbf2 ,blanco1 #bbb2 ,boreal1 #aeb2 distribution1 #ach2 ,eocene1 #eed2 ,john ,day1 #bdi1 #ebh2 marine1 #ei2 migration to ,s4 ,amer41 #ejh1 #eah2 ,miocene1 #bbi1 #bcc1 #bch2 ,neotropical1 #agc2 ,pleistocene1 ,n4 ,amer41 #bjc1 #baj2 ,s4 ,amer41 #baa2 ,plioc41 #bbb2 ,sonoran1 #afc2 ,uinta1 #bfe2 ,white ,river1 #bed1 #cab ,carnivores1 see ,carnivora ,carolozittellia1 #dfb1 #dhh ,carpincho1 #ahc 7fig471 #ahe4 7,see also ,capybara and ,water ,hog7 ,carpus1 #hb ,casa ,mayor age and stage1 #bj1 #aab1 #bha1 #dhh1 #dii1 #eab ,cascade ,mts41 #aba2 ,oligocene craters of1 #aaf ,,castle1 ,w4 ,e41 #feg1 #ffj ,castor1 #if1 #aec1 #aeg 7fig47 ,castoroides1 #aie1 #bje ,cat1 #bbb2 ,domestic1 #edf 7manus fig47 ,catamarca age and stage1 #bj1 #abi1 #bbf ,catarrhina1 #ehc1 #ehg1 #ehh ,cats1 #ed1 #ei1 #ij1 #agf1 #eag1 #eah1 #eai1 #ecj1 #ecb1 #eec1 #efh2 cursorial1 #edc2 ,miocene1 #ede2 ,native1 #fcd1 #fch1 #fdj2 ,oligocene1 #ecj2 ,pleistocene1 #ede2 ,pleisto4 ,s4 ,amer41 #baa1 #bab2 ,pliocene1 #bbc1 #ede2 ,south ,america1 #eeb2 true1 #bdi1 #eag1 #ecj1 #edc4 7,see ,felid7 ,cattle1 #ie2 spread of1 #adb ,caves as sources of fossil mammals1 #cj ,cavia1 #ahc 7fig471 #ahe ,cavicornia1 #cbh1 #daa1 #dab1 #daf1 #dba ,cavies1 see ,caviid ,caviid1 #ahe1 #feg2 ,araucanian1 #bbf2 ,pleistocene1 #bah2 ,santa ,cruz1 #bde ,cavy1 ,rock1 #ahc 7fig47 ,caxomistle1 see ,cacomistle ,cebid1 #agb1 #egh1 #ehd1 #ehe ,cebus1 #bah1 #egh1 #ehd 7fig471 #ehe ,celebes1 #egi ,cement1 #if ,cenozoic era1 #ae1 #af1 #ag1 #ah1 #ii2 ,south ,america1 #ai ,centetes1 #agc ,central1 #hc ,central ,america1 #abc1 #afd1 #agh1 #agi1 #cbj1 #ehe2 ,eocene1 #ajd1 #aab2 geology1 #abj2 mammals1 #ada2 ,oligocene1 #aac1 #aag2 ,paleocene1 #ajc2 tapirs1 #acg2 ,tertiary1 #bb2 zology1 #adf ,central ,american subregion1 #afd1 #agj 7map71 #aia ,cerdocyon1 #aga 7fig471 #agd1 #eag1 #eeb ,cervalces1 #aie 7restoration71 #bjh1 #bji 7restoration71 #cfb1 #dac ,cervicornia1 #daa1 #dba ,cervid1 #cfb1 #daa1 #ffa2 ,neotropical1 #agi4 7,see also ,deer7 ,cervulus1 #dab ,cervus1 #bjh1 #cfb2 ,c4 canadensis1 #aea1 #aee 7fig471 #bjb1 #bjh1 #daa1 #dab2 ,c4 elaphus1 #aea2 ,c4 eustephanus1 #aea4 7,see ,deer7 ,cetacea1 #fj1 #ddb2 ,miocene1 #abc1 #abe ,chtomys1 #ahd ,chalicothere1 #bdj 7restoration71 #cef 7manus fig47 ,chalicotheres1 see ,chalicotheriid ,chalicotheriid1 #fj1 #bdg1 #bia1 #ced1 #chc1 #che1 #deh1 #dhd1 #fea2 ,bridger1 #ceg2 ,john ,day1 #bej1 #ceg2 ,miocene1 #bca1 #bce1 #bch1 #cef2 ,white ,river1 #beg1 #ceg ,chalicotherium1 #ced ,,chamberlin1 ,t4 ,c41 #acj ,chamois group1 #bjb1 #dag2 subfamily1 #aeb ,champsosaurus1 #ajb ,cheeta1 #edb1 #edc ,chelodactyla1 #fj1 #bij ,chevron-bones1 #gc ,chevrotains1 #ed1 #fj1 #djh 7see also ,mouse-,deer and ,tragulina7 ,chili1 #abd1 #ahd1 #dcf2 marine rocks1 #aab2 ,pleistocene1 #bj2 ,pleisto4 glaciation1 #acc ,chilian subregion1 #afd1 #agj 7map7 ,chinchilla1 #ahd 7fig471 #ahe ,chinchilla-family1 ,araucanian1 #bbf ,chinchillas1 #ahe2 ,santa ,cruz1 #bde ,chipmunks1 #ada1 #aec ,chironectes1 #fbf1 #fbg ,chiroptera1 #ei ,chlamydophorus1 #aij1 #eib ,chlamydotherium1 #bah1 #eib1 #eif1 #fab1 #fad ,cholpus1 #gd1 #ahg 7fig471 #eia ,chronology1 geological1 #aj2 of rocks1 #f ,civet cats1 #eah1 #eeh 7see ,viverrid7 ,cladoclinus1 #fbg ,cladosictis1 #bdc 7restoration71 #fbg1 #fch1 #fci 7restoration7 ,clnodon1 #eed1 #efa ,classification of mammals1 #ej ,clavicle1 #gg 7fig47 ,clawed mammals1 #ei1 #gd1 #def1 #dei1 #dfj1 #dib1 #ead ,climate1 as barrier to species1 #adj2 determining distribution1 #bd2 ,cretaceous1 #bf2 ,eocene1 #aji1 #ddh2 ,miocene1 #abb2 ,mioc4 of ,patagonia1 #abd1 #bdd1 #ehf2 ,oligocene1 #aaf2 ,paleocene1 #ajb2 ,pleistocene1 #aaf1 #acd1 #aib2 ,pliocene1 #abg2 vicissitudes of1 #ajj ,climatic changes1 #ad2 affecting distribution1 #adj2 evidences of1 #bd2 ,pleisto41 effects on migrations1 #bjg ,coast ,range1 elevation1 #abb2 ,miocene1 #aac1 #abe ,coati1 #afb ,coatis1 #gf1 #bac1 #eag1 #edf1 #eeb ,cochlops1 #eib ,coendou1 #ahb 7fig471 #ahd ,colodon1 #beg1 #bia1 #cbg ,colombia1 #fbf1 #fdj ,colonoceras1 #bgb1 #bia1 #cdg1 #cej ,colouration1 animal1 #de ,colpodon1 #dfb ,columbia ,river valley1 ,miocene1 #aah ,comparative ,anatomy1 #fdg ,conard ,fissure1 #cj1 #baj ,condylarth1 #bgh 7restoration71 #deg 7skeleton fig471 #dei 7restoration7 ,condylarthra1 #fj1 #ddc1 #def1 #dhd1 #dib1 #dii1 #ejh1 #ead1 #eae1 #fec2 ,puerco1 #bhf1 #dfj2 ,torrejon1 #bhe1 #dei2 ,wasatch1 #bgg1 #deg2 ,wind ,river1 #bgd1 #def ,condylura1 #aeb ,conepatus1 #agd 7fig471 #bac1 #eag1 #eeb ,conies1 #fj1 #deh1 #dha ,conifers1 #ajc ,continental deposits1 ,eocene1 #ajf1 #aab2 ,miocene1 #abj2 ,oligocene1 #aac1 #aag2 ,paleocene1 #aja2 ,pliocene1 #abg1 #abh ,continental islands1 #adj ,continuity of development1 #ffj ,convergence1 #fej1 #fec1 #fee1 #fef ,,cope1 ,e4 ,d41 #cjf1 #cdc1 #cii1 #djj1 #dja ,coracoid1 #gf ,coryphodon1 #bge1 #bgg1 #bgi 7restoration71 #bhe1 #ddc1 #deb1 #ded1 #def ,coryphodontid1 #bhe1 #ddc1 #ded2 lower ,eocene1 #def ,coryphodonts1 see ,coryphodontid ,costa ,rica1 #aha2 ,pliocene1 #abh ,cotton-rats1 #afc ,coyote1 #afb1 #afe 7fig47 ,coyotes1 ,pleistocene1 #bah ,cramauchenia1 #dhi ,creodont1 #beb 7restoration71 #efc 7restoration7 ,creodonta1 #ei1 #eaf1 #eai1 #ebg1 #ebi1 #eed1 #egd2 ,bridger1 #bfh1 #bga 7restoration72 ,eocene1 #fcc2 ,paleocene1 #fcc2 ,puerco1 #bhf2 ,torrejon1 #bhe2 ,uinta1 #bfe2 ,wasatch1 #bgf2 ,white ,river1 #bec2 ,wind ,river1 #bgd4 7,see ,flesh-eaters7 ,cretaceous period1 #ae1 #af1 #ajc1 #aab1 #aag1 #bfa1 #bha1 #ddc1 #dfj1 #ead1 #fdb1 #fdc2 climate1 #bf ,crocodiles1 #abb1 #bdd2 absent from ,john ,day1 #aaf2 ,eocene1 #aaa2 ,paleocene1 #bhd2 ,white ,river1 #aaf ,crown of tooth1 #ie ,crustal movements1 ,miocene1 #abb ,ctenomys1 #ahd ,cuba1 #agc1 #ahe2 junction with ,central ,america1 #abh1 #eih2 ,miocene1 #abc2 ,pleistocene1 #acd1 #fjd2 ,pliocene1 #abh1 #fje ,cuboid1 #hi ,culebra ,cut1 ,tertiary rocks1 #bb ,cuneiform1 #hc1 #hi ,,cuvier1 ,g41 #dd1 #fed ,cyclopes1 #eia ,cyclopidius1 #cfa1 #cgf ,cynodesmus1 #eag1 #ebb 7skull fig471 #ebc1 #ecj ,cynodictis1 #bed1 #eag1 #ebi 7restoration71 #ecj1 #edg ,cyon1 #bac1 #eag1 #ebg ,cyonasua1 #eag ,dama1 #dab ,daphnodon1 #eag1 #ebe 7restoration71 #ebf1 #ecj ,daphnus1 #bed1 #eag1 #ebc 7skull fig471 #ebd 7manus and teeth fig471 #ebf1 #ebh1 #ecj1 #ecg1 #edf ,,darwin1 ,c41 #cc1 #ce1 #eb1 #acf1 #acg1 #adc1 #aic1 #bag1 #dfc1 #dhi1 #dij1 #dia1 #dib ,dasypoda1 #ahi1 #eib1 #faj4 7,see also ,armadillos7 ,dasypodid1 #eib ,dasyprocta1 #ahe 7fig47 ,dasypus1 #ahi 7fig471 #eib1 #faa1 #fad1 #faf ,dasyures1 ,australian1 #fch ,dasyurid1 #fcb1 #fcd1 #fdj ,deep ,river age and stage1 #ag1 #aba1 #bcc ,deer1 #df1 #ed1 #fj1 #ie 7molar fig471 #bbb1 #cab1 #cai1 #cfj 7molar fig471 #cfb1 #dji1 #daa1 #dfa2 ,american1 #aec1 #afb1 #bjb1 #bjh1 #dji1 #dab1 #dad1 #dbj1 #feg2 ,axis1 #dab2 ,barking1 #dab2 ,black-tailed1 #e1 #bjb2 ,chinese ,water-1 #dab2 earliest1 #feh2 ,fallow1 #dab2 ,florida1 #agi 7fig472 ,hog1 #dab2 hornless1 #dad2 ,marsh1 #agi1 #ahj 7fig472 ,miocene1 #bcb1 #bce1 #dad 7restoration72 ,mule1 #df 7fawns fig471 #afg 7fig472 ,musk-1 #bbd1 #dab1 #feh2 ,neotropical1 #agi2 ,north ,american1 #agi2 ,old ,world1 #aea1 #agi1 #aha1 #bjb1 #dab1 #dae2 ,pampas1 #ahj2 ,patagonian1 #ia 7pes fig471 #daj 7manus and pes fig472 ,pleistocene1 #bjb1 #bjh1 #dab2 ,pleisto41 ,s4 ,amer41 #bac1 #bae2 ,pliocene1 #bbd1 #bbf2 ,south ,american1 #dae1 #dah1 #dff2 southern1 #dab1 #dac2 ,tertiary1 #dab1 #dai2 ,virginia1 #d1 #aff 7fig471 #agi1 #bjb1 #dab ,deer-,antelopes1 #bjb1 #bbd1 #cfb1 #dag2 ,miocene1 #bcb1 #bce1 #dad1 #dae 7restoration72 ,pleistocene1 #dag ,degu1 #ahd ,deltatherium1 #eed ,dental formula1 #ic ,dentine1 #if ,deposits1 continental 7see ,continental deposits72 lake1 #cg2 river1 #cf ,dermoptera1 #ei ,deseado age and stage1 #bj1 #aag1 #bhb1 #bhc1 #dgd1 #dge1 #dgg1 #dgi1 #dha1 #dhe1 #dhf1 #dhg1 #ejh1 #eaa1 #eab1 #ehf1 #ehg ,desiccation1 ,miocene and ,pliocene1 #abh ,desmathyus1 #cfa ,desmatippus1 #bij ,deuterotherium1 #dhi ,development1 convergent1 #ddf1 #dii2 parallel1 #dii2 per saltum1 #ffa4 7,see also ,evolution7 ,devonian period1 #ae2 glaciation in1 #be ,dhole1 #bac1 #bdi1 #eag1 #ebg1 #ecj ,diadiaphorus1 #bdh1 #dhi1 #eja 7skull fig471 #ejb 7restoration71 #ejc 7pes fig471 #eje1 #ejg1 #ejh ,diceratheres1 see ,diceratherium ,diceratherium1 #bch1 #bci 7restoration71 #bej1 #bef1 #bia1 #ccc1 #ccd1 #cej1 #ddd ,dicerorhinus1 #cbg1 #cbi ,dichobunid1 #cfa1 #cih ,didelphia1 #eg1 #ei1 #fbf ,didelphiid1 #fbg1 #fcj ,didelphis1 #afa1 #fbf1 #fbg1 #fca2 ,d4 marsupialis1 #afa 7fig471 #fca ,didolodid1 #dhi ,didolodus1 #dhi ,didymictis1 #eee1 #eeh ,digit1 #ij ,digital reduction1 #feh ,digitigrade1 #ij ,dinictis1 #bed1 #eag1 #ech1 #eci 7restoration71 #eda 7pes fig471 #edb1 #edf ,dinocerata1 #ddc ,dinocynops1 #eag ,dinocyon1 #ebd ,dinohyus1 #bci1 #cfa1 #cff ,dinosaurs1 #ajc1 #bhd ,dinotheres1 see ,dinotherium ,dinotherium1 #dce1 #dch1 #dhf ,diplacodon1 #bff1 #bia1 #cac1 #cag 7head restored7 ,dipodomys1 #afc 7fig47 ,diprotodonta1 #ei1 #fbg1 #fdj2 ,deseado1 #fdb2 ,paran1 #fda2 ,pleistocene1 #fda2 ,pliocene1 #fda2 ,santa ,cruz1 #fdj1 #fda2 ,south ,american1 #fdj ,discontinuity of development1 #ffj ,dispersal of species1 #adc ,dissacus1 #eed1 #efj ,distribution1 discontinuous1 #abg1 #ach1 #aic2 geographical1 of mammals1 #ace ,divergence1 see ,evolution ,ddicurus1 #bab 7restoration71 #bai1 #fah1 #fai 7restoration7 ,dog1 #ij1 #eec2 family1 #eeh2 fox-like1 #ebi 7restoration7 ,dogs1 #ij1 #agc1 #eag1 #eai1 #ebj1 #edh1 #eec1 #eed1 #eeh2 ,blanco1 #ebb2 early1 #eej2 ,john ,day1 #bdi1 #ebc1 #ebh1 #ebi2 ,miocene1 #bbi1 #bcd1 #bch1 #ebb1 #ebg1 #ebh1 #ebi2 ,oligocene1 #ebc1 #edg1 #eec2 ,paran1 #bbg2 ,pleistocene1 #eba2 ,pleisto41 ,s4 ,amer41 #bab2 ,pliocene1 #ebb2 ,plioc4 ,s4 ,amer41 #bbf2 primitive1 #ecg2 short-faced1 #ecj2 ,south ,american1 #eeb2 ,uinta1 #bfe2 ,white ,river1 #bed1 #ebi4 7,see also ,canid7 ,dolichorhinus1 #bgb1 #bia ,dolichotis1 #ahe ,dolphins1 #cg1 #fj1 #id1 #fef2 ,miocene1 #abc ,domesticated plants1 history of1 #bhh ,douroucoulis1 #egh1 #ehe ,drainage1 the ,pleistocene changes of1 #acb ,drift-sheets1 #be1 #acb ,dromocyon1 #bfi 7restoration71 #bga 7restoration71 #eed1 #eei ,dromomeryx1 #bce1 #bcg 7restoration71 #cfb1 #dag ,drought1 effects of on mammals1 #cc ,duck-billed ,mole1 #eg1 #ei ,dugong1 #fj1 #ddb ,duplicidentata1 #ei ,dust1 volcanic1 #bi2 wind-blown1 #cc ,east ,indian ,archipelago1 #aia ,echidna1 #eg ,echimys1 #ahd ,ecuador1 #agh1 #bhd1 #cia1 #edh1 #fbf1 #fdj2 ,pleistocene1 #bj1 #baa2 ,pliocene1 #abi ,edentata1 #fj1 #gb1 #ge1 #ia1 #ig1 #abj1 #ahe1 #bfg1 #cee1 #eia2 ,araucanian1 #bbf2 armoured1 #fj1 #eib1 #faj2 ,casa ,mayor1 #bhc1 #eib1 #eie2 ,deseado1 #bfa1 #eie2 distribution1 #ach2 ,eocene1 ,n4 ,amer41 #eig1 #faf2 hairy1 #fj1 #eia2 ,old ,world1 #ahe1 #eia2 ,paran1 #bbg2 ,pleisto41 ,n4 ,amer41 #bje2 ,pleisto41 ,s4 ,amer41 #bah1 #eif2 ,plioc41 ,n4 ,amer41 #bbe1 #eig2 ,plioc41 ,s4 ,amer41 #bbf1 #eif2 ,santa ,cruz1 #bde1 #eif2 ,south ,american1 #bgf1 #fbe ,edentates1 see ,edentata ,edvardocopeia1 #eji ,egg-laying mammals1 #ei ,egypt1 #bed1 #cgj1 #dbb1 #dcb1 #ddb1 #dej1 #ehg2 ,eocene1 #bcd2 ,oligocene1 #bcd1 #bfd1 #ehc ,ei-1 #ehe ,,eigenmann1 ,c4 ,h41 #fed ,elachoceras1 #ddc1 #ddi1 7skull fig471 #dej1 #dea1 #dee ,elasmotherium1 #cej1 #cea ,elephant1 #eij2 ,african1 #dbc 7molar fig472 ,columbian1 #aie 7restoration71 #aig1 #aih 7restoration71 #dbg1 #dcj2 ,east ,african1 #dbe2 ,imperial1 #aii1 #dbg1 #dhe2 ,indian1 #ig 7section of tooth fig471 #aig1 #dbc1 #dbe 7manus fig471 #dbf 7section of fore foot fig472 tribe1 #hb2 ,west ,african1 #dbe ,elephantid1 #dcb ,elephants1 #de1 #fj1 #gc1 #ia1 #ib1 #ie1 #ig1 #bae1 #bfd1 #cab1 #dcf1 #ddf1 #ddh1 #dfe1 #dhg1 #fed2 ,american1 #dcj2 cranial bones of1 #fc2 distribution1 #ach2 hairy1 #ddh1 proboscis of1 #fe2 ,pleistocene1 #aif1 #baa1 #dbf2 ,siberian ,pleisto41 #ci2 true1 #dbc1 #dch1 #dci2 tusks of1 #ig ,elephas1 #dcf1 #dcg 7head and tooth fig472 ,e4 columbi1 #aie 7restoration71 #aig1 #aih 7restoration71 #dbg2 ,e4 imperator1 #aii1 #dbg1 #dhe2 ,e4 maximus1 #ig 7section of molar fig471 #aig1 #dbc1 #dbe 7manus fig472 ,e4 primigenius1 #aif1 #bjg1 #ccb1 #dbf ,elk1 #ej1 #ada1 #aea1 #aee 7fig472 ,scandinavian1 #aea ,elms1 #ajb ,embrithopoda1 #fj ,embryology1 #fdh ,emigrants from ,n4 ,amer4 to ,old ,world1 #bee1 #bef1 #def ,enamel1 #if ,england1 early ,man in1 #ehh2 ,paleocene flora1 #ajc2 ,pliocene1 #abg ,enhydrocyon1 #eag1 #ebh1 #ecj ,entelodon1 #cfi ,entelodontid1 #bej1 #cfa1 #cff1 #dde2 ,wasatch1 #bha ,entelodonts1 see ,entelodontid1 also ,giant ,pigs ,entelonychia1 #fj1 #bdg1 #dfb1 #dhb1 #feb2 ,casa ,mayor1 #bhb2 ,deseado1 #bfc4 7,see also ,homalodotheres7 ,entrerios1 #abh ,eoanthropus1 #ehh ,eobasileus1 #ddc1 #ddi1 #dea1 #dee ,eocardia1 #bdc ,eocene epoch1 #ag1 #ajd2 climate of1 #bf2 close of1 #aaa2 ,europe1 #bfb1 #cgj1 #deb1 #efb1 #ffa2 ,north ,america1 #ajd1 #aje 7map71 #bja1 #bej1 #bea1 #bec1 #bgc1 #bhg1 #bia1 #cbe1 #cfi1 #dba1 #eai1 #ebi1 #eed1 #eeg1 #egd1 #fdd2 ,south ,america1 #bj1 #aab1 #bfa1 #bha1 #dgg1 #dha1 #dhb1 #dhe1 #dhg1 #dhh1 #ejh1 #eji1 #eab1 #ead1 #fbe1 #fdb ,eodidelphys1 #fbg ,eohippus1 #bhj1 #bij1 #cjb1 #cjc 7restoration71 #cjd1 #cje 7skull fig471 #cjg 7manus and pes fig471 #cjh ,eohyus1 #bha ,eomoropus1 #bia1 #ceg ,eotitanops1 #bge1 #bia1 #cae ,eotylopus1 #beg1 #cfb ,epigaulus1 #bbc 7restoration7 ,epihippus1 #bij1 #cja1 #cjb ,epithelium1 #bbg1 #dhi1 #ejh ,epoch1 geological1 #ae ,eporeodon1 #cfa1 #cge1 #cgi ,equid1 #bij1 #bia4 7,see also ,horses7 ,equus1 #ie1 #aii1 #bac1 #bbc1 #bia1 #bie1 #cje 7skull fig471 #cjf 7manus and pes fig472 ,american species1 #bif2 ,e4 asinus1 #eb2 ,e4 burchelli1 #bjj2 ,e4 caballus1 #eb1 #aii1 #bac1 #bie2 ,e4 fraternus1 #aii2 ,e4 giganteus1 #bjj1 #bja1 #bie2 ,e4 occidentalis1 #bjj2 ,e4 pacificus1 #bja2 ,e4 pectinatus1 #bjj2 ,e4 przewalskii1 #eb1 #bib 7fig472 ,e4 scotti1 #aie 7restoration71 #bjj 7do472 ,e4 semiplicatus1 #bjj2 ,south ,american species1 #cjg2 ,e4 tau1 #aii1 #bie ,equus ,beds1 #cc1 #aca1 #acc1 #bjj1 #bje4 7,see ,sheridan7 ,era1 geological1 #ae ,erethizon1 #aea 7fig471 #aec1 #ahb1 #ahd1 #bje ,eriodes1 #egh ,ermine1 #aeb1 #aei 7fig47 ,ethiopian region1 #adf ,euceratherium1 #bjb1 #cfb1 #dah ,eucholops1 #fjg ,eucinepeltus1 #eib1 #fbc ,euprotogonia1 #deg1 #dei ,eurasia1 #aaj1 #edh ,europe1 #bec1 #bed1 #bee1 #bfg1 #bgb1 #bgf1 #bgg1 #bhj1 #bha1 #bhd1 #bhg1 #bia1 #cjc1 #cbc1 #cbd1 #cbe1 #cdj1 #cej1 #cea1 #ced1 #cef1 #ceg1 #cfi1 #cgj1 #chj1 #dag1 #dah1 #dai1 #dba1 #dbb1 #dcb1 #dce1 #deb1 #def1 #dhf1 #ecd1 #ech1 #edc1 #ede1 #edf1 #eeb1 #eed1 #eeg1 #efa1 #fdb1 #fdd2 caverns of1 #cj2 circumpolar area1 #adh2 ,eocene1 #ajd2 ,eoc4 separation from ,asia1 #ajd2 human habitation of1 #ehh2 loess of1 #acc2 mammals of1 #ade2 ,mammoth in1 #aig2 pre-,eocene immigration into1 #ajh2 ,miocene1 #bce2 ,mioc4 climate1 #abb2 ,pleisto4 glaciation1 #acc2 tapirs in1 #ach2 ,triassic1 #fdb2 zology of1 #adf ,eusmilus1 #bed1 #eag1 #ech ,eutatus1 #eib1 #eif1 #fab1 #fac ,eutheria1 #eg1 #ei ,eutrachytherus1 #bfc1 #dfb1 #dgg ,extinction of species1 #ac1 #baa ,evolution1 of ,amblypoda1 #ded2 of camels1 #djj2 convergent1 #fdi1 #fej1 #fee2 of ,creodonta1 #egd2 divergent1 #ah1 #aci1 #fej1 #fee2 of ,fissipedia1 #eec2 of horses1 #cje1 #cbe1 #djj2 irreversibility of1 #eda1 #fef2 modes of ,mammalian1 #fde2 of oreodonts1 #cha2 parallel1 #cic1 #fdi1 #fee2 of ,proboscidea1 #dcf1 #dcg 7diagram72 of rhinoceroses1 #cea2 of tapirs1 #cbd2 of titanotheres1 #caf1 #cbe ,fallow ,deer1 #df ,families1 distribution of1 #ach ,fauna1 #ef2 ,araucanian1 #bbf2 ,bridger1 #bfe1 #bfg1 #bgc1 #cae2 ,deseado1 #bfa1 #fch2 mid4 ,eocene1 #bfg2 ,john ,day1 #bdi2 low ,miocene1 #bcg2 ,neotropical1 #bhc1 #faj2 ,oligocene1 #bcg2 ,paran1 #bbg2 ,pleistocene1 ,n4 ,america1 #aic1 #bjg2 ,pleisto41 ,s4 ,amer41 #baa1 #bbf1 #eig2 ,puerco1 #bhe2 ,santa ,cruz1 #bf1 #abd1 #bdb1 #fch2 ,torrejon1 #bhd2 ,uinta1 #bfe1 #bgc2 ,wasatch1 #bgf2 ,white ,river1 #bea1 #bfe1 #bff2 ,wind ,river1 #bgd1 #bge1 #cae ,faunas1 ,casa ,mayor1 #bha1 #bhc2 ,eocene1 ,n4 ,amer41 #bfe2 ,eoc41 ,s4 ,amer41 #bha2 ,miocene1 #bbi2 ,oligocene1 ,n4 ,amer41 #bdi2 ,oligo41 ,s4 ,amer41 #bfa2 ,paleocene1 #bhc1 #bhf1 #fdd2 ,pliocene1 ,n4 ,amer41 #bba2 ,plioc41 ,s4 ,amer41 #bbe2 ,quaternary1 ,n4 ,amer41 #aic2 ,quat41 ,s4 ,amer41 #baa2 successive mammalian1 #aib2 ,tertiary1 #bba2 ,tertiary1 ,s4 ,amer41 #dfa ,fawns1 #df 7fig47 ,faym1 #dcb ,felid1 #ed1 #eag1 #eah1 #ecj ,felin1 #ed1 #bed1 #ece1 #edb1 #edc1 #fej2 ,miocene1 #bbi1 #bcd1 #bch1 #eda1 #ede2 origin of1 #fei2 ,pleistocene1 #bjd1 #ede2 ,pliocene1 #ede ,felis1 #ed1 #eag1 #edc1 #ede1 #edf2 ,f4 atrox1 #bjd1 #ede2 ,f4 concolor1 #afh 7fig471 #edd 7skull fig471 #ede 7dentition fig472 ,f4 domestica1 #edf 7manus fig472 ,f4 imperialis1 #bjd2 ,f4 leo1 #bjd2 ,f4 onca1 #agf1 #agg 7fig471 #eeb2 ,f4 pardalis1 #agf 7fig471 #eeb ,femur1 #hd1 #he 7fig47 ,ferret1 ,black-footed1 #afj 7fig47 ,fiber1 #aec ,fibula1 #hf1 #hg 7fig47 ,field-mice1 #ada ,,filhol1 ,h41 #ecd ,fisher1 #aeb ,fishers1 #ada1 #eah ,fishes1 ,florissant1 #aba2 ,green ,river1 #aji2 ,panama marine1 #bc2 ,south ,american fresh-water1 #feb2 teeth of1 #ib ,fissipedia1 #ei1 #eaf1 #eag1 #eec1 #eed1 #eee1 #eef1 #eeg1 #eeh1 #efc1 #egf ,flesh-eaters1 primitive1 #ei1 #eed2 ,santa ,cruz1 #fcg ,florida1 island1 #abb2 ,miocene1 #aag2 ,oligocene1 #aac2 ,paleocene1 #aja2 ,pliocene1 #abe1 #abg ,florissant formation1 #aba ,,flower1 ,w4 ,h41 #chi1 #cij1 #daa1 #dab1 #dai ,flying ,lemur1 #ei ,forests1 ,oligocene1 #ech2 ,paleocene1 #ajb2 petrified1 #abb ,fort ,union stage1 #ag1 #ii1 #ajb1 #fdb ,fossils1 #g1 #bi2 classification1 #ee2 entombment1 #bi2 evidence of climate1 #be2 mammals1 #fa ,fossorial habits1 #b ,fox1 #aia2 ,arctic1 #adh1 #adi 7fig471 #aej 7fig472 ,grey1 #afe 7fig471 #eag2 ,red1 #aeh 7fig471 #eag ,foxes1 #ada1 #agc1 #eah1 #ebj1 #ecj1 #eeb2 grey1 #afb2 ,pleistocene1 #bjd2 red1 #aeb2 ,white ,river1 #bed1 #ebi ,france1 #bef1 #ccc1 #cfd1 #dda1 #egd2 ,eocene1 of1 #ajh2 ,oligocene1 #fag ,frankstown ,cave1 #cj ,friasian fauna1 #eji ,f,,rbringer1 ,m41 #fee ,gait1 varieties of1 #ij ,galapagos ,archipelago1 #acf ,ganodonta1 #fbe ,garzonia1 #fbg1 #fda 7jaw fig47 ,garzoniid1 #fbg ,gazelle1 bones of1 #ce ,gazelle-,camel1 #bda1 #bdb 7restoration71 #cic1 #cid1 #djh ,genera1 origin of1 #fed ,generic area1 #acg ,genetic series1 #ef ,genetics1 #fdh ,genus1 #ec ,geographical changes affecting distribution1 #aci ,geology1 #e ,geomys1 #afc ,geomyid1 #bfe ,giant ,pig1 #beb 7restoration71 #bfj 7do47 ,giant ,pigs1 #bej1 #bei1 #bff1 #cfa1 #cff2 ,bridger1 #bgc1 #cgj2 ,john ,day1 #bei1 #cfg2 ,miocene1 #bci1 #cff1 #cfi2 ,oligocene1 #bha1 #cfh2 ,uinta1 #cfi2 ,wasatch1 #bha1 #cgj2 ,white ,river1 #bei1 #cfg ,,gidley1 ,j4 ,w41 #cc1 #bjb1 #fdb ,giraffe1 #gj1 #gi1 #ceh1 #chi ,giraffe-,camel1 #bcf 7restoration71 #cia1 #cib 7restor47 ,giraffe-camels1 #bce1 #chh1 #cid2 ,miocene1 #bca1 #bda1 #cid2 ,pliocene1 #bbd1 #chh ,giraffes1 #ed1 #chi1 #dji1 #daa ,glacial1 accumulations1 #be2 climate1 #be1 #bf2 periods1 #ad1 #be2 stages1 #ag1 #acj2 theory1 #abi ,glaciation1 ,pleistocene1 #be1 #acj2 causes of1 #acd ,glaciers1 ,pleistocene1 #aca ,glossotherium1 #fjb ,glyptodon1 #bab 7restoration71 #bai1 #eib1 #fah1 #fai 7restor471 #fba ,glyptodont1 ,santa ,cruz1 #bdc 7restoration71 #fjf 7do47 ,glyptodontia1 #fj1 #bde1 #bdf1 #eib1 #eic1 #eid1 #eie1 #fag2 ,araucanian1 #bbf2 ,astraponotus1 #bha1 #eie1 #fbe2 ,deseado1 #bfb1 #eie2 ,pampean1 #bab 7restorations71 #fai 7restorations71 #fbc2 ,paran1 #bbg2 ,pleistocene1 ,n4 ,amer41 #bje1 #bjf1 #baa1 #eig1 #eih2 ,pleisto41 ,s4 ,amer41 #bah1 #bba1 #eif1 #eig1 #fbj1 #fbd2 ,pliocene1 ,n4 ,amer41 #bba1 #bbe1 #eif2 ,plioc41 ,s4 ,amer41 #eif1 #fbb1 #fbd2 ,santa ,cruz1 #bde1 #eif1 #fbb1 #fbc ,glyptodontid1 #eib ,glyptodonts1 see ,glyptodontia ,glyptotherium1 #bba1 #eib ,gnawing mammals1 #ei ,goat1 ,rocky ,mt41 #aeb1 #aeh 7fig471 #bjb1 #daf ,goats1 #cfb1 #dji1 #daf ,gomphotherium1 #bbi1 #dcj1 #dca 7head restored71 #dcd1 #dcf1 #dcg 7head and molar fig471 #dch1 #dci ,gopher1 ,horned1 #bbc 7restoration7 ,grasses1 #bgc2 ,paleocene1 #bhd ,grassy plains1 spread of1 #bcc ,gravigrada1 #ia1 #abj1 #cee1 #eia1 #eib1 #eih1 #fab2 ,pleistocene1 ,n4 ,amer41 #bje1 #eig2 ,pleisto41 ,s4 ,amer41 #bah1 #eih2 ,santa ,cruz1 #fje1 #fjg1 #fji1 #faj4 7,see also ,ground-,sloths7 ,great ,basin1 #cbb2 ,pleistocene of1 #aca ,great ,britain1 #ba1 #adj1 #dah ,great ,plains1 #cc1 #bjj1 #bbi1 #bce1 #cbb1 #chf1 #dcb2 ,miocene1 #aba2 ,oligocene climate1 #aaf2 ,pleistocene1 #aca ,greenland1 #aja1 #ajc1 #baj2 ,pliocene1 #abe ,green ,river stage1 #aji ,,gregory1 ,j4 ,w41 #ce ,,gregory1 ,w4 ,k41 #fda ,grison1 #age 7fig471 #eag1 #eeb ,ground-,sloth1 giant1 #aie 7restoration71 #fjc 7restoration72 ,pleistocene of ,cuba1 #eih2 ,santa ,cruz1 #bdc 7restor471 #fjf 7restor472 skin of1 #dj1 #fjb ,ground-,sloths1 #ge1 #ia1 #abj1 #bfg1 #cee1 #eia1 #eib1 #eic1 #eid1 #eie1 #eih2 ,araucanian1 #bbf2 ,astraponotus1 #eie2 ,casa ,mayor1 #bhd1 #eie2 ,deseado1 #bfb1 #eie2 ,miocene1 #fji2 ,mioc41 ,n4 ,amer41 #eig2 ,pampean1 #bab 7restoration71 #bbj 7do471 #fje1 #fjh1 #fji2 ,paran1 #bbg2 ,pleistocene1 ,n4 ,amer41 #bje1 #bjf1 #baa1 #bai1 #eig2 ,pleisto41 ,s4 ,amer41 #bah1 #bai1 #bba1 #eif1 #eih1 #fjd1 #fje2 ,pliocene4 ,n4 ,amer41 #bba1 #bbe1 #eig2 ,plioc41 ,s4 ,amer41 #eif1 #eih2 ,santa ,cruz1 #bde1 #bdf1 #eif1 #eih1 #fje1 #fjh1 #fji4 7,see also ,gravigrada7 ,ground-squirrels1 #afd1 #aha ,grypotherium1 #eib1 #fjb ,guanaco1 #fj1 #aci1 #agh1 #chi 7fig471 #cii 7skull and tooth fig471 #djj 7manus fig471 #dja 7pes fig471 #dij1 #dia2 destruction by cold1 #cf2 distribution1 #ach ,guiana1 #agi ,guianas1 ,miocene1 #eif ,guinea-,pig1 #ahe2 four-toed race1 #feg1 #ffj ,gulf-coast1 ,eocene1 #ajd1 #aaa1 #aag2 ,miocene1 #aag2 ,pliocene1 #abe ,gulf of ,mexico1 ,eocene1 #ajf1 #aac2 ,oligocene1 #aac1 #aag2 ,paleocene1 #aja ,gulf ,stream1 ,oligocene1 #aac ,gulo1 #aeb1 #aee 7fig471 #bcg1 #eag ,gypsy ,moth1 #adc ,,haeckel1 ,e41 #fdh ,hairless skin1 #de ,halicore1 #ddb ,halmarhiphus1 #fbg ,handwriting1 development of1 #i1 #ac1 #ad ,hapale1 #egh ,hapalid1 #agb1 #egh1 #ehb1 #ehc ,hapalops1 #bdc 7restoration71 #eib1 #fje1 #fjf 7restor471 #fji 7pes fig47 ,hare1 ,arctic1 #aej ,hares1 #ei1 #aha1 #bde1 #bdi2 ,miocene1 #bbi1 #bch2 ,plioc41 ,n4 ,amer41 #bbb2 ,plioc41 ,s4 ,amer41 #bbf2 tailless1 or whistling1 #aec ,harpagolestes1 #eed1 #eei1 #efj1 #ega ,harrison stage1 #abj1 #bce ,,hatcher1 ,j4 ,b41 #ccg1 #ebc1 #ebd ,hayti1 #agc1 #ahe2 junction with ,centr4 ,amer41 #abh2 ,miocene1 #abc2 ,pliocene1 #abh ,hedgehogs1 #ei1 #bgf2 ,white ,river1 #bec ,hegetotheriid1 #dfb1 #dgb ,hegetotherium1 #dfb1 #dgi ,helaletes1 #bgb1 #bia ,helohyus1 #bgc1 #cfa1 #cfe ,hemiacodon1 #egh ,hemipsalodon1 #bec1 #efe ,henricosbornia1 #dfb ,heptodon1 #bge1 #bia1 #cbg ,herbivora1 #eaf ,herbivorous mammals1 #de2 large1 #dd ,hipparion1 #bia ,hippidion1 #bab 7restoration71 #bac1 #bad 7restor471 #bia1 #bif1 #cjg1 #cjh 7skeleton fig47 ,hippocamelus1 #ia 7pes fig471 #ahj1 #daj 7manus and pes fig47 ,hippopotamus1 #de1 #ed1 #fj1 #gj1 #ib1 #ceh1 #fed ,hogs1 ruminating1 #cgb ,holarctic region1 #adf1 #adg1 #aej1 #ehh ,homacodon1 #bgc1 #cfa1 #cih ,homalodontotheriid1 #dfb2 ,casa ,mayor1 #bhc ,homalodontotherium1 #dfb1 #dhb ,homalodothere1 #dhb ,homalodotheres1 #dfb1 #dhb1 #eji ,homo heidelbergensis1 #ehh2 ,h4 neanderthalensis1 #ehh2 ,h4 sapiens1 #ehh ,homunculus1 #egh1 #ehf ,hoofed animals1 #gd1 #gg1 #ha1 #hc1 #hi1 #cab1 #cac1 #dfa2 ,araucanian1 #bbg2 ,bridger1 #bfi1 #bgc2 ,casa ,mayor1 #bhb2 clawed1 #fea2 ,deseado1 #bfb1 #bfd2 massive1 #fed2 ,miocene1 #bbi1 #bcd2 ,paran1 #bbh2 ,pleistocene1 ,n4 ,amer41 #aii2 ,pleisto41 ,s4 ,amer41 #bac2 primitive1 #dib2 ,santa ,cruz1 #bdf2 ,torrejon1 #bhe2 ,uinta1 #bgc2 ,wasatch1 #bgg2 ,wind ,river1 #bgd 7see ,ungulata7 ,hoofed mammal1 clawed1 #dhd ,hoofed mammals1 #fj1 #def1 #dei1 #dfj2 even-toed1 #ed1 #fj2 odd-toed1 #fj2 ,white ,river1 #bee 7see ,ungulata7 ,,hooker1 ,j41 #aic ,hoplophoneus1 #beb 7restoration71 #eag1 #ece1 #ecf 7restoration71 #eci1 #edj1 #edc ,horn-cores1 #daf ,horse1 #dd1 #dh1 #eb1 #fb1 #gf 7scapula fig471 #gi 7humerus fig471 #ha 7fore-arm bones fig471 #he 7femur fig471 #hg 7leg-bones fig471 #ie 7molar fig471 #bid1 7manus and pes fig471 #cei2 ,asiatic ,wild1 #eb1 #bib 7fig472 ,dawn1 #cjb1 #cjc 7restoration72 forest1 #bjj2 ,pampas1 #bab 7restoration71 #bad 7restoration71 #cjh 7skeleton fig472 ,texas1 #aie 7restoration71 #bjj 7restoration72 three-toed grazing1 #bih 7restoration72 ,true1 #aii1 #bac1 #bie2 ,white ,river1 #beb 7restoration71 #cjj 7restoration74 7,see also ,equus7 ,horses1 #ef1 #fj1 #ha1 #ie1 #ig1 #bhi1 #bij1 #bia1 #cab1 #cai1 #ccj1 #cec1 #cfj1 #chb1 #cig1 #deh1 #dfa1 #dii1 #ejd1 #fea1 #fec1 #fee1 #fef1 #feh1 #ffa2 ,blanco1 #bbb2 bones of1 #cc2 ,bridger1 #bgb1 #cjb2 browsing1 #bbc1 #bca1 #bce1 #big1 #bih2 ,eocene1 #cjd1 #cjg2 grazing1 #bbc1 #bca1 #bce1 #big1 #bih2 ,john ,day1 #bii2 ,miocene1 #bie1 #big1 #bih1 #bca1 #bcb1 #bcd1 #bch1 #cja2 ,north ,american1 #ci2 ,oligocene1 #bii2 phyla of1 #bhi1 #fej2 ,pleistocene1 ,n4 ,amer41 #aii1 #bjh1 #baa1 #bac1 #bba1 #bie1 #cjd1 #cjg2 ,pleisto41 ,s4 ,amer41 #bac1 #bae1 #cjg2 ,pliocene1 #bbc1 #bie1 #cjg1 #cca2 ,south ,american1 #cjg2 spread of1 #adb1 #adc2 three-toed1 #cc1 #eja2 tridactyl1 #feh2 true1 #bib1 #cjh2 ,uinta1 #cja2 ,wasatch1 #bhj1 #cjb2 ,white ,river1 #beg1 #bii1 #cjj2 ,wind ,river1 #bge1 #cjb1 #cjc1 #cif4 7,see also ,equid7 ,,horsfall1 ,r4 ,b41 #db ,,hrdli,,ka1 ,a41 #ehi ,hudsonian fauna1 #aea ,hudson's ,bay slope1 interglacial forests1 #aca ,huemul1 #ahj ,humerus1 #gh 7fig47 ,humid province1 #afd ,humidity1 effect on distribution1 #ada ,hungary1 #caf ,hutias1 #ahd ,,huxley1 ,t4 ,h41 #bh ,hynid1 #eah ,hynodon1 #beb 7restoration71 #bec1 #eee1 #efb1 #efc 7restoration71 #efd 7skeleton fig471 #efe 7teeth fig471 #eff 7teeth fig471 #efg1 #egf ,hynodont1 primitive1 #efg 7restoration7 ,hynodontid1 #bec1 #eee1 #eeg1 #efb1 #efe 7teeth fig471 #eff 7teeth fig471 #efi1 #egc1 #ege2 ,bridger1 #bfh2 ,eocene1 #bed1 #eff1 #egf2 ,wind ,river1 #bgd ,hynodonts1 see ,hynodontid ,hynognathus1 #ebb1 #ebd1 #ecj ,hydrochrus1 #ahc 7fig471 #ahe1 #bje ,hydropotes1 #dab ,hyena1 bones of1 #ce ,hyena-dogs1 #bbb1 #bdi1 #ebg1 #ecj ,hyenas1 #eah1 #ebg1 #eec1 #eed ,hyoid arch1 #fg ,hyopsodonta1 #ei ,hyperhippidium1 #bac1 #bia1 #cjg ,hyperleptus1 #fjg ,hypertragulid1 #bfg1 #cfb1 #chf1 #djb1 #dad2 ,eocene1 #djh2 ,john ,day1 #bea1 #djd1 #djg2 ,miocene1 #bda1 #beh1 #djd2 ,white ,river1 #beh1 #djf1 #djh ,hypertragulids1 see ,hypertragulid ,hypertragulus1 #bda1 #beh1 #bfg1 #cfb1 #djg1 #djh ,hypisodus1 #beh1 #cfb1 #djh ,hypohippus1 #bia1 #big1 #cjj ,hypsodont teeth1 #ie 7fig472 prevalence of1 #bcb ,hyrachyus1 #bga 7restoration71 #bgb1 #bia1 #cci1 #cdd 7restor471 #cde 7skull fig471 #cdf1 #cdi1 #cej ,hyracodon1 #beb 7restoration71 #bee1 #bff1 #bia1 #cda 7restor471 #cdc 7manus fig47 ,hyracodontid1 #bia1 #djc ,hyracodontin1 #bia1 #cdj1 #cda1 #cdf1 #cej1 #cea1 #ceb2 ,bridger1 #bgb1 #cdc2 ,eocene1 #cdb2 ,uinta1 #bff1 #cdc2 ,white ,river1 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cancrivorus1 #eeb2 ,p4 lotor1 #aec1 #aff 7fig471 #edg 7dentition fig471 #eeb2 ,p4 ursinus1 #eeb ,procyonid1 #eag1 #eah1 #edf2 ,miocene1 #bch1 #edg2 ,south ,american1 #eeb ,prodasypus1 #eib ,proectocion1 #dhi ,proeutatus1 #eib1 #fad1 #fae 7skull fig47 ,proglires1 #ei ,promerycochrus1 #bce1 #bea1 #cfa1 #cge1 #cgf 7restoration7 ,pronesodon1 #bfb1 #dfb ,prong ,buck1 #bjb1 #bbe1 #daf1 #dag1 #dbj4 7,see ,antelope1 ,prong-horned7 ,pronomotherium1 #bca1 #cfa1 #cgd1 #cge 7head restored71 #cgf1 #cha ,propalohoplophorus1 #bdc 7restoration71 #eib1 #fjf 7restor471 #fbc ,propolymastodon1 #fbg ,propyrotherium1 #dfb1 #dhg ,prosthennops1 #cfa ,protagriochrus1 #bfg1 #cfa1 #chc1 #che ,protapirus1 #beg1 #bia1 #cbc 7skull fig471 #cbd 7head restored71 #cbe 7teeth fig47 ,proteodidelphys1 #fbg ,proterothere1 single-toed1 #ejf 7restoration72 three-toed1 #ejb 7restor47 ,proterotheres1 see ,proterotheriid ,proterotheriid1 #bbg1 #bdh1 #dhi1 #dii1 #ejg1 #fec2 ,araucanian1 #bbg1 #ejh2 ,deseado1 #bfd1 #dhi2 ,paran1 #bbh1 #dii2 ,santa ,cruz1 #bdh1 #eja ,proterotherium1 #bdh1 #dhi1 #ejd ,protheosodon1 #dhi1 #dii ,prothoatherium1 #dhi ,prothylacynus1 #bdc 7restoration71 #bdd1 #fbg1 #fce1 #fcf 7restor471 #fcg ,protitanotherium1 #bff1 #cac ,protobradys1 #eib1 #eie ,protoceras1 #beb 7restoration71 #beh1 #cfb1 #dje 7restor471 #djf 7skull fig471 #djg1 #dde ,protodonta1 #ei ,protogonodon1 #deg ,protohippus1 #bia1 #cje 7skull fig471 #cjf 7manus and pes fig47 ,protolabis1 #cfb1 #cia ,protomeryx1 #bda1 #bea1 #cfb1 #cia ,protopithecus1 #bah ,protoreodon1 #bfg1 #cfa1 #chj 7skull fig471 #cha ,prototheria1 #eg1 #ei1 #gf ,protylopus1 #bfg1 #cfb1 #cig1 #cii 7skull and tooth fig471 #djj 7manus fig471 #dja 7pes fig47 ,protypotherium1 #bdc 7restoration71 #dfb1 #dgi1 #dhj 7restor47 ,province1 zological1 #ade ,prozadius1 #eib ,pseudlurus1 #eag1 #ede ,pseudocladosictis1 #fbg ,pseudolabis1 #cfb ,pseudolestodon1 #eib ,pterodon1 #bec1 #eee1 #efe 7teeth fig471 #eff 7do471 #efg1 #egf ,ptilodus1 #fbg1 #fdb 7skull fig471 #fdc 7head restored7 ,pudu1 #ahj ,pudua1 #ahj ,puerco age and stage1 #ag1 #ii1 #aja1 #ded1 #dfj1 #efa ,puma1 #afh 7fig471 #bab1 #edd 7dentition fig471 #ede 7skull fig472 ,south ,american1 #eeb ,pumas1 #aec1 #afc1 #agf2 ,pleistocene1 #bjd ,pyramidal1 #hc ,pyrenees1 #ajd ,pyrotheres1 see ,pyrotheria ,pyrotheria1 #fj1 #dfb1 #dhe1 #ejj2 ,casa ,mayor1 #bhc1 #dhh2 ,deseado1 #bfb1 #dhe ,pyrotherium1 #bfd1 #dfb1 #dhe1 #dhf 7head restored7 ,pyrotherium ,beds1 #bj1 #aag1 #bfa1 #dhf ,quadrumana1 #ehb ,quadruped1 #a ,quaggas1 #bib ,quaternary period1 #ae1 #ag1 #fa1 #ajj1 #abi1 #bfg1 #cai2 ,south ,america1 #ai ,quicksands1 burial of mammals in1 #cg ,rabbit1 #bah ,rabbits1 #ei1 #ada1 #adb1 #afd1 #bde2 ,white ,river1 #bed ,raccoon1 #aec1 #afb1 #afc1 #aff 7fig471 #age1 #edg 7dentition fig471 #eec2 ,crab-eating1 #eeb ,raccoon-family1 ,miocene1 #bch2 ,pliocene1 ,s4 ,amer41 #bbf ,raccoons1 #e1 #ij1 #bac1 #eag1 #eah1 #eai1 #edf1 #eec2 ,miocene1 #bbi1 #edg2 ,paran1 #bbg2 ,pleistocene1 #bjd2 ,tertiary1 #edg ,race1 geographical1 #eb ,radius1 #hj ,raised beaches1 #aac1 #acd ,rancho ,la ,brea1 #ca ,rangifer1 #gj1 #aeb1 #aeg 7fig471 #bjb1 #bjh1 #cfb1 #dab ,ratel1 #eea ,rats1 #fj1 #bde2 fish-eating1 #ahb2 ,pleisto41 ,s4 ,amer41 #bah2 spiny1 #ahd ,rattlesnake stage1 #abg ,,ray4 ,j41 #ea ,realm1 zological1 #ade ,recent epoch1 #ag1 #acb1 #cce1 #ccf2 ,south ,american1 #ai ,reduction of parts1 #fef ,region1 zological1 #ade ,reindeer1 #gj1 #ada1 #dab2 ,lapland1 #aeb2 ,pleistocene1 #bg ,reptiles1 see ,reptilia ,reptilia1 #ee2 as ancestral to mammals1 #fdc2 distribution1 #ada2 ,mesozoic1 #bhd2 ,oligocene1 #aag2 ,paleocene1 #bhd2 ,santa ,cruz1 #bdd2 teeth of1 #ib2 ,triassic of ,s4 ,africa1 #fdd ,republican ,river age1 #ag1 #abg ,restorations1 how made1 #db ,rheithrodon1 #ahb ,rhinoceros1 #cej1 #dij1 #dib2 ,african1 #cbg1 #cbh1 #cbi1 #ccg2 aquatic1 #cdg 7restoration72 ,bornean1 #dd2 ,broad-lipped1 #cbi1 #cea1 #ddh2 cursorial1 #beb 7restor471 #cda 7do471 #cdc 7manus fig471 #cdd 7restor472 hornless1 #beb 7restor471 #bef 7do471 #cce 7skull fig472 ,indian1 #dd1 #cbg1 #cbh1 #cbi2 ,javan1 #cbg1 #cbh 7skull fig471 #dgc2 paired-horned1 #bci 7restor472 primitive1 #bga 7restor472 small-horned1 #bcj 7restor472 ,sumatran1 #cbg1 #cbi2 ,white1 #cbi2 ,woolly1 #ccb ,rhinoceros1 #cbg2 ,r4 sondaicus1 #cbg1 #cbh 7skull fig471 #dgc2 ,r4 unicornis1 #cbi ,rhinoceroses1 #de1 #ef1 #fj1 #fc1 #ia1 #bhi1 #cab1 #chb1 #dfa1 #eaj1 #fed1 #fee1 #ffa2 ,african1 #cdf2 aquatic1 #bia1 #cdj2 aquatic1 ,bridger1 #bgb2 aquatic1 ,uinta1 #cdh2 aquatic1 ,white ,river1 #cdf2 bones of1 #ce2 cursorial1 #bia1 #cdj2 cursorial1 ,bridger1 #bgb1 #cdc2 cursorial1 ,uinta1 #bff2 cursorial1 ,white ,river1 #bee1 #cdj2 cursorial1 ,wind ,river1 #bge2 ,eocene1 #cch1 #cci2 hairy1 #ddh2 ,john ,day1 #bej1 #bef1 #ccc2 ,miocene1 #bcj1 #bcd1 #bch1 #bef1 #ccb1 #ccc2 ,north ,american1 #ci1 #aii2 ,oligocene1 #ccc2 ,pliocene1 #bbd1 #cca2 paired-horned1 #bef1 #ddd2 phyla of1 #bhi1 #fej2 ,siberian1 #ci2 true1 #bia1 #cbf1 #cdj1 #cdf1 #cej1 #cea2 true1 ,uinta1 #bff2 true1 ,white ,river1 #bee1 #ccc2 ,white ,river1 #bee1 #ccc ,rhinocerotid1 #bia1 #cbf1 #cdj1 #cej ,rhynchippus1 #dfb ,ribs1 #gd 7fig472 sternal1 #gd ,rio de ,la ,plata1 #abh ,river deposits1 #cf ,robin1 #ej ,rocky ,mts41 #aja1 #aej1 #aec2 ,pleistocene glaciers1 #aca ,rodent1 primitive1 #bga 7restoration72 ,santa ,cruz1 #bdc 7do47 ,rodentia1 #e1 #ei1 #bhb1 #bhc1 #bhd1 #dei1 #fbi2 ,araucanian1 #bbf2 ,boreal1 #aec2 ,bridger1 #bgj2 ,deseado1 #ehg2 distribution1 #ach2 ,john ,day1 #bdi2 jumping1 #ij2 ,miocene1 #bbi1 #bcc1 #bcg2 ,neotropical1 #ahc 7figs472 ,paran1 #bbg2 ,pleistocene1 #acd1 #bje2 ,pleisto41 ,s4 ,amer41 #bah2 ,pliocene1 #bbb2 ,santa ,cruz1 #bde2 simplicidentate1 #fbh2 ,sonoran1 #afc2 ,south ,american1 #aha2 ,uinta1 #bfe2 ,wasatch1 #bhj2 ,white ,river1 #bed2 ,wind ,river1 #bge2 ,west ,indian1 #aia ,rodents1 see ,rodentia ,roots of teeth1 #ie ,rootless teeth1 #if ,rosebud stage1 #abj1 #bce ,ruminants1 #ha1 #hd1 #hg1 #bha1 #cgc1 #fea2 hollow-horned1 #cbh2 ,miocene1 #bcb2 true1 #ed1 #bja1 #cfb1 #chg1 #djb1 #dji1 #ddf ,,russell1 ,i4 ,c41 #ehi ,sables1 #ada ,sabre-tooth1 #cb2 cat1 #beb 7restoration72 cats1 #fei2 false1 #edb 7skull fig472 primitive1 #eci 7restor472 ,tiger1 frontispiece 7restor471 #aie 7restor471 #eag1 #eca 7skull fig471 #ecd 7do471 #ecf 7restor472 tigers1 #ed1 #baj1 #ecj1 #eeb2 ,miocene1 #bbi1 #bcd1 #ecd2 ,oligocene1 #ece2 ,pleistocene1 #bjd2 ,pleisto41 ,s4 ,amer41 #baa2 ,pliocene1 #bbc ,sabre-tooths1 #bfe1 #fej2 false1 #bdi1 #eda2 ,john ,day1 #bdi1 #ece1 #eda1 #edb2 ,miocene1 #bch2 ,white ,river1 #bed4 7,see also ,machairodontin7 ,sacramento ,valley1 ,miocene1 #aah ,sacrum1 #gc 7fig47 ,sadypus1 #eib ,sagittal crest1 #fc ,saiga1 #fe ,saiga ,antelope1 #fe ,st4 ,elias ,alps1 #aja ,st4 ,lawrence ,valley1 invasion of1 by sea1 #acc ,sakis1 #egh1 #ehe ,saline water1 #cd ,,salisbury1 ,r4 ,d41 #acj ,salt ,lake1 ,utah1 #aca ,salt lakes1 #bd ,sand1 wind-blown1 #cc ,santa ,cruz age and stage1 #bj1 #cj1 #abd1 #bfb1 #bfc1 #bfd1 #bhb1 #bhc1 #dfg1 #dgj1 #dgc1 #dgd1 #dge1 #dgg1 #dgi1 #dha1 #dhb1 #dhe1 #dic1 #dii1 #ejj1 #eja1 #ejd1 #ejh-eab1 #ehf1 #ehg2 mammals1 #bdc 7restorations7 ,santa ,cruz ,mts41 ,calif41 #aah ,santa ,cruz ,river1 as barrier to armadillos1 #aci ,sapajou1 #ehd 7fig47 ,sarcophilus1 #fcd ,,sarmiento1 #adc ,scalibrinitherium1 #dhi1 #dic1 #die1 #dif 7skull fig471 #dig 7do47 ,scalops1 #afc ,scalpriform teeth1 #if 7fig47 ,scapanus1 #afc ,scaphoid1 #hc ,scapho-lunar1 #hc ,scapula1 #gf 7fig47 ,scelidotherium1 #eib1 #fja1 #fjb1 #fjd ,schismotherium1 #eib ,schizotherium1 #bia1 #ceg ,,schlosser1 ,m41 #bfb1 #chj1 #ead1 #eee1 #ehc1 #fbe1 #ffa ,,schuchert1 ,c41 #aje1 #aad1 #aai1 #abf ,sciuravus1 #bhj ,sciuromorpha1 #bgj ,sciuropterus1 #afd ,sciurus1 #afd 7fig47 ,sclerocalyptus1 #bai1 #eib1 #fah1 #fbj ,scleropleura1 #eib1 #faa ,,scott1 ,d4 ,h41 #bhh ,sea-,cow1 #fj1 #bjg1 #ddb ,sea-,otter1 #eag1 #eah ,seals1 #a1 #b1 #c1 #cg1 #ef1 #ei2 ,pleistocene1 #acb ,seas1 barriers to land mammals1 #aci ,section1 geological1 #g1 #i 7diagram7 ,sedimentary rocks1 #f ,sediments1 #f ,selenodont tooth1 #cfj 7fig472 origin of1 #fea ,sewellel1 #aec1 #bcc ,sewellels1 #bdi2 ,miocene1 #bch ,shales1 ,florissant1 #abi2 ,green ,river1 #aji ,sheep1 #ed1 #fj1 #ic1 #cfb1 #dji1 #daf1 #dah1 #dai1 #dbj2 ,rocky ,mt41 #aeb1 #dai ,shells1 fossil1 #ffb ,sheridan stage1 #cc1 #aca1 #acc1 #bjj ,shrews1 #ei1 #ada1 #agc1 #aia2 ,american1 #afc2 jumping1 #ei2 ,old ,world1 #aeb2 tree1 #ei ,siberia1 #aig1 #bjg1 #ccb1 #cej1 #dbf2 frozen carcasses in1 #ci ,sierra ,nevada1 #aja1 #abb1 #aej1 #aec2 ,miocene1 #aah2 ,pleistocene glaciers1 #aca ,sigmodon1 #afc ,silurian period1 #ae ,simiid1 #ehc ,simplicidentata1 #fj ,,sinclair1 ,w4 ,j41 #ajg1 #dcg ,sinopa1 #efe 7teeth fig471 #eff 7do471 #fcc ,sirenia1 #fj1 #ddb ,sitomys1 #aec1 #afd1 #ahb ,skeleton1 #fa2 significance of1 #db ,skull1 #fa ,skunk1 #afc1 #afg 7fig471 #bac1 #eag2 ,argentine1 #agd 7fig472 ,little1 #agd 7fig472 ,spotted1 #eag ,skunks1 #aec1 #afc1 #agd1 #baj1 #eah1 #eej1 #eea2 ,pleistocene1 #bjd2 ,south ,american1 #eeb ,sloth1 ,three-toed1 #ahf 7fig471 #eia2 ,two-toed1 #gd1 #ahg 7fig471 #eia ,sloths1 #b1 #fj1 #ig1 #ahf1 #ahi1 #eib2 ,araucanian1 #bbf2 ,pleistocene1 #bah2 ,santa ,cruz1 #bde ,smilodon1 frontispiece 7restoration71 #aie 7do471 #bjd1 #baa1 #eag1 #eca 7skull fig471 #ecb 7teeth fig471 #ece1 #ecf1 #ecg1 #edd1 #eec1 #fbb ,,smith1 ,,perrin1 #bc ,,smith1 ,,william1 #g1 #i ,smith ,river stage1 #aba ,snake ,creek age and stage1 #ag1 #abg1 #bbb1 #chh ,snakes1 #bdd2 ,paleocene1 #bhd ,solenodon1 #agc 7fig47 ,solitary species1 #ch ,sonoran region1 #adf1 #adg 7map71 #aeb1 #aec1 #afa1 #agf1 #agh1 #aia1 #cfc ,sorex1 #aeb ,south ,africa1 #ad2 ,permian glaciation1 #be2 ,triassic reptiles1 #fdd ,south ,america1 ,eocene separation from ,n4 ,amer41 #ajd2 ,miocene junction with ,n4 ,amer41 #abj2 ,permian glaciation1 #be2 ,pleistocene ,man1 #ehi2 zological divisions1 #agc 7map72 zology1 #adf ,south ,australia1 dry lakes of1 #cd ,south ,shetland ,islands1 #abd ,sparnacian stage1 #ajh ,species1 definition1 #ea2 distribution1 #acf2 origin1 #bj ,specific area1 #acf ,spermophilus1 #afc 7fig471 #afd ,sphenophalus1 #cfb ,spilogale1 #agd 7fig471 #eag1 #eeb ,spiny rats1 ,pleistocene1 #bah ,sports1 #ffj ,squirrel1 ,grey1 #afd 7fig472 suborder1 #bgj ,squirrels1 #b1 #fj1 #bde2 flying1 #afd2 ,john ,day1 #bdi2 ,miocene1 #bbi1 #bch2 true1 #afd1 #aha2 ,white ,river1 #bed ,stag1 #ceh2 ,european1 #aea2 ,thian ,shan1 #aea ,stag-,moose1 #aie 7restoration71 #bjh1 #bji 7restor471 #dac ,stage1 geological1 #ae ,stalagmite1 #cj ,stations1 #acf ,stegodon1 #dcj1 #dci ,stegodonts1 #dch ,stegotherium1 #bdc 7restoration71 #dhj 7do471 #eib1 #fad1 #fae 7skull fig47 ,stenomylus1 #bda1 #bdb 7restoration71 #cfb1 #cic1 #djh ,sternum1 #ge 7fig47 ,stibarus1 #cfa ,,stirling1 ,e4 ,c41 #cd1 #ce ,straits1 of ,lombok1 #ace2 of ,magellan1 #adc ,stratified rocks1 #f ,stream-channels1 ,white ,river1 #aac ,stylinodon1 #bgd ,stypolophus1 #eee ,subregion1 zological1 #ade ,subsidences1 ,pleistocene1 #acb ,subungulata1 #ead ,suillines1 #ffa ,suina1 #ed1 #fj1 #cfa1 #cfb ,sumatra1 #ba1 #adj1 #cbg ,superposition of beds1 #g1 #h 7diagram7 ,sus1 #cei 7fore-arm bones fig471 #cfc ,swamps1 burial of mammals in1 #cc ,swan1 #gj ,swine1 #ed1 #fj2 ,american1 #cfc2 ,old ,world1 #cfc1 #cfd2 ,pleistocene1 #bja2 true1 #cfd1 #cfe4 7,see also ,peccaries7 ,swine-like animals1 #cfa1 #cfb ,sycamores1 #ajb ,symbos1 #bjh1 #cfb1 #dah ,synaptomys1 #aec ,syndyoceras1 #bda1 #beh1 #cfb1 #djc 7restoration71 #djd1 #djf1 #djg ,syria1 #dha ,systemodon1 #bhj1 #bia1 #cbd ,tniodontia1 #fj1 #bgf1 #fbe2 ,bridger1 #bfg2 ,puerco1 #bhf2 ,wind ,river1 #bgd ,tagassu1 #afa1 #agg 7fig471 #agh1 #cfj 7tooth fig471 #cfa1 #cfc 7dentition fig471 #cfd ,tagassuid1 #cfa1 #cfc ,takin1 #dah ,taligrada1 #ddc ,tamandua1 #ahg1 #ahh 7fig471 #eia ,tamias1 #aec ,tapir1 #dg 7fig4 of young71 #ha 7fore-arm bones fig471 #hg 7leg-bones fig471 #bhi 7manus fig471 #bij 7pes fig471 #cbj 7adult fig471 #cba 7skull fig471 #dga1 #dij1 #dib2 ,asiatic1 #cba2 ,pinchaque1 #cbb2 ,white ,river1 #cbc 7skull fig471 #cbd 7head restored7 ,tapiravus1 #bia ,tapirid1 #fj1 #fe1 #hi1 #ada1 #agf1 #bhi1 #bia1 #cab1 #cae1 #cai1 #ccj1 #cda1 #cdh1 #cei1 #dfa1 #fea1 #fec2 ,american1 #cbb2 ,bridger1 #bgb2 distribution1 #acg2 ,eocene1 #cbc2 ,john ,day1 #bej2 ,miocene1 #bca1 #bcd1 #cbb2 ,north ,american1 #ci2 ,oligocene1 #cbc1 #cci2 ,pleistocene1 #aii1 #bja1 #bjh1 #baj1 #cbb2 ,pleisto41 ,s4 ,amer41 #bac1 #bae2 ,pliocene1 #bbc1 #cbb2 ,south ,american1 #cbd2 ,uinta1 #bff2 ,wasatch1 #bhj1 #cbd2 ,white ,river1 #beg1 #cbb ,tapiroid1 #bgb1 #cae ,tapiroids1 #cba ,tapirs1 see ,tapirid ,tapirus1 #agf1 #bia2 ,t4 haysii1 #bja1 #cbb2 ,t4 roulini1 #cbb2 ,t4 terrestris1 #dg 7young fig471 #hg1 #bja1 #bhi 7manus fig471 #bij 7pes fig471 #cbj 7adult fig471 #cba 7skull fig471 #cbb1 #cbe 7upper teeth fig47 ,tardigrada1 #ahf1 #eia1 #eib1 #faj2 ,araucanian1 #bbf4 7,see also ,sloths7 ,tarija ,valley1 ,pliocene1 #abi1 #bbe ,tar-pools1 #ca2 ,pleistocene1 #cb ,tarsier1 #bha1 #ehj ,tarsiids1 #ehc ,tarsius1 #bha1 #ehj ,tarsus1 #hh ,tasmania1 #ach1 #fcb1 #fcd ,tasmanian ,devil1 #fbg1 #fcd2 ,wolf1 #dc1 #bbf1 #bdd1 #fbf1 #fcb1 #fcc 7fig47 ,tatu1 #afj1 #aij 7fig471 #eib1 #eic1 #fab ,taurotragus1 #bjb ,taxidea1 #aec1 #afb1 #afh 7fig471 #eag ,tayra1 #age 7fig471 #bac1 #eag1 #eeb ,teeth1 #ib2 importance of fossil1 #ch ,teleoceras1 #bia1 #cca1 #ccb1 #ccc1 #cej ,telmatherium1 #bia ,temnocyon1 #eag1 #ebh1 #ecj ,temperature as a barrier to species1 #adj1 #ada ,tenrecs1 #agc ,tephrocyon1 #eag1 #ebb1 #ebg1 #ecj ,tertiary period1 #ae1 #ag1 #ai1 #ii1 #bfg1 #cai1 #cfi1 #dac1 #dfj1 #eca2 ,central ,america1 #bb2 ,culebra1 #bb2 ,great ,plains1 #cf2 ,patagonia1 #bj2 ,south ,america1 #bj1 #bdh1 #dfa1 #dfc2 ,tierra del ,fuego1 #bj ,terrestrial habit1 #b ,tetrabelodon1 #dcj1 #dcg ,thalarctus1 #adh 7fig47 ,theosodon1 #bdc 7restoration71 #bdh1 #dhi1 #dic1 #did 7restor471 #dif 7skull fig471 #dig 7do471 #dih 7manus fig47 ,thian ,shan1 #dai ,thinohyus1 #cfa ,thoatherium1 #bdc 7restoration71 #bdh1 #dhi1 #ejj1 #eja1 #ejd1 #eje 7skull fig471 #ejf 7restor471 #ejg 7pes fig47 ,thomashuxleya1 #dfb1 #dhe ,thomomys1 #afd ,thorax1 #gd ,thousand ,creek age and stage1 #ag1 #abg ,thylacine1 #dc1 #fcb1 #fcc 7fig471 #fcd1 #fce4 7,see also ,tasmanian ,wolf7 ,thylacynid1 #fbg1 #fcb ,thylacynus1 #dc1 #bbf1 #bdd1 #fcb1 #fcc 7fig47 ,tibet1 #bbd1 #dah ,tibia1 #hf1 #hg 7fig47 ,tierra del ,fuego1 #bj1 #agh ,tiger1 #de ,tillodontia1 #ei1 #bgf2 ,bridger1 #bfg2 ,wasatch1 #bgf2 ,wind ,river1 #bgd ,time1 geological1 #af ,titanothere1 #bec 7restoration71 #bga 7do471 #cji 7do471 #cad 7restor4 and fig4 of molar7 ,titanotheriid1 #bia1 #cjh1 #cag 7heads restored71 #ccd1 #ceb1 #cec1 #ceg1 #cff1 #dde1 #ddf1 #deh1 #dfe1 #fed1 #ffa2 ,bridger1 #bgj1 #cac2 ,oligocene1 #caj1 #cad1 #cae1 #cci2 ,uinta1 #bff1 #cac2 ,white ,river1 #bee1 #caj1 #cac1 #cae2 ,wind ,river1 #bge1 #bgf1 #cae ,titanotherium1 #bec 7restoration71 #bia1 #cji 7restor471 #caj 7molar fig471 #caa 7skull fig471 #cag 7head restored71 #cah 7fig4 of manus7 ,tolypeutes1 #ahi1 #eib1 #faa1 #faf ,toronto1 interglacial beds near1 #acj ,torrejon age and stage1 #ag1 #ii1 #aja1 #bhf1 #dec1 #efa ,tortoises1 #bdd2 ,paleocene1 #bdd ,toxodon1 #bab 7restoration71 #bae1 #bag 7restor471 #dfb1 #dfc1 #dff 7skull fig471 #dfg1 #dfh1 #dfi1 #dga1 #dgb 7pes fig471 #dgc1 #dgg1 #dhg ,toxodont1 #dih2 horned1 #bbh 7head restored71 #bfc 7do472 ,pampean1 #bab 7restoration71 #bag 7do472 ,santa ,cruz1 #bdc 7restor471 #dfg 7skull fig472 ,santa ,cruz horned1 #dgd 7restor47 ,toxodonta1 #fj1 #bhb1 #dfb1 #dfc1 #dgg1 #dhb1 #dhc1 #dhg1 #ejj1 #eji1 #eaa1 #feb2 ,araucanian1 #bbg2 ,deseado1 #bfb1 #bfd1 #dgd2 ,paran1 #bbh2 ,santa ,cruz1 #bdf1 #dfg ,toxodontia1 #fj1 #cee1 #dfa1 #dgh1 #dhe1 #dhi1 #dib1 #ejj1 #ead2 ,pleistocene1 #bae1 #bba ,toxodontid1 #dfb1 #dgd ,toxodonts1 see ,toxodonta ,tragulina1 #ed1 #fj1 #djh1 #dji1 #daj4 7,see ,mouse-,deer7 ,transition zone1 #adg 7map71 #aec ,trapezium1 #hc ,trapezoid1 #hc ,tree-sloths1 #eia1 #eic1 #eid1 #eie1 #eif1 #fji2 ,pleistocene1 #eif2 ,santa ,cruz1 #eif4 7,see also ,sloths7 ,tremarctos1 #agb1 #agf 7fig471 #eag1 #edh1 #eeb ,trves1 #aj ,triassic period1 #ae1 #af1 #fdb1 #fdc2 climate1 #bd ,triconodonta1 #ei ,trier1 cathedral of1 #aj ,trigodon1 #bbg1 #bbh 7head restored71 #dfb1 #dff1 #dgc1 #dgd ,trigonias1 #bef1 #bia1 #ccf1 #ccg 7skull and front teeth fig471 #cch1 #cci 7manus fig471 #cea ,trigonolestes1 #bha1 #cfa1 #cih ,trigonolestid1 #cfa ,trigonostylopid1 #eji1 #eab ,trigonostylops1 #eji ,triisodon1 #eed1 #efa ,trilophodon1 #bbi ,trinidad1 #agj ,trinomial system of nomenclature1 #eb ,triplopus1 #bff1 #bgb1 #cdc 7manus fig471 #cde ,tritemnodon1 #bga 7restoration71 #eee1 #efe 7teeth fig471 #eff 7do471 #efg 7restor471 #egf1 #fcc ,trituberculata1 #ei ,tropical species1 distribution1 #ada ,tse-tse ,fly1 #adb ,tuatara1 #bhd ,tubulidentata1 #fj ,tuco-tuco1 #ahd ,tuff1 ,miocene1 #aab1 #abb2 ,santa ,cruz1 #abd ,turkestan1 #dai ,turtles1 #ajb ,tusks1 #ib ,tylopoda1 #ed1 #fj1 #cfb1 #chf1 #dji1 #daj2 ,pleistocene1 #bjb ,typothere1 #bdc 7restoration71 #dhj 7do471 #fcf 7do471 #fci 7do47 ,typotheres1 see ,typotheria ,typotheria1 #fj1 #bae1 #cgb1 #dfb1 #dgf2 ,araucanian1 #bbg2 ,casa ,mayor1 #bhb1 #dgi2 ,deseado1 #bfc1 #bfd2 ,paran1 #bbh2 ,pleistocene1 #bae1 #bba1 #dgf2 ,santa ,cruz1 #bdf1 #dgi2 ,tertiary1 #bae ,typotheriid1 #dfb1 #dgf ,typotherium1 #bae1 #bag1 #bfc1 #dfb1 #dgf1 #dgg ,uakaris1 #egh1 #ehe ,uinta age and stage1 #aa1 #ag1 #aaj1 #bgj1 #bga1 #bgb1 #cja1 #cci1 #cde1 #cdi1 #cfe1 #cfi1 #cgj1 #chj1 #chc1 #che1 #chf1 #cig-djj1 #dji1 #ddc1 #eai1 #ebg1 #ebi1 #eeg1 #eei1 #egc1 #egi ,uinta ,mts41 #ajf1 #ajh2 ,pleistocene glaciers1 #aca ,uintacyon1 #eee1 #eeh ,uintatheres1 see ,uintatheriid ,uintatheriid1 #bhe1 #ddc1 #ddd1 #dde 7skull fig471 #dea1 #deb1 #ded1 #dfe1 #eji1 #ecb2 ,bridger1 #bfi1 #ddc2 ,wasatch1 #bgi1 #dea2 ,wind ,river1 #bgd1 #dej ,uintatherium1 #ea1 #bga 7restoration71 #ddc1 #ddd1 #dde 7skull fig471 #ddg 7restoration7 ,ulna1 #hj ,unciform1 #hc ,unconformity1 #cab ,ungual phalanx1 #hd ,ungulata1 #fj1 #eac1 #eaf2 primitive1 #dfj2 ,santa ,cruz1 #dha1 #eaa2 short-footed1 #ddc2 ,south ,american indigenous1 #dfa1 #dff1 #dfi1 #dhf1 #dhi1 #dij1 #ejj1 #eji1 #eaa1 #eac1 #ead2 ,white ,river1 #beh ,ungulates1 see ,ungulata ,unguligrade1 #ia ,university of ,california1 #ca1 #cb ,upheavals1 ,pleistocene1 #acb1 #acc2 ,pliocene1 #acb ,upper ,sonoran zone1 #adh1 #afd ,ural1 ,mts41 #ajf2 ,sea1 #ajf1 #ajh ,urocyon1 #afb1 #afe 7fig471 #eag ,urotrichus1 #aec ,ursid1 #eag1 #eah1 #edh ,ursus1 #ij 7pes fig471 #aef 7fig471 #afc1 #eag1 #edi ,uruguay1 #ehe ,variant1 #ec ,varieties1 #eb1 #ffb ,vegetation1 ,eocene1 #aaa2 ,paleocene1 #bhc4 7,see also ,flora and ,plants7 ,vermilingua1 #ahg1 #eia ,vertebra1 #fh2 caudal1 #gc 7fig472 cervical1 #gj 7fig472 dorsal1 #fi 7fig471 #gb 7fig472 lumbar1 #gb1 #gc 7fig472 sacral1 #gc 7fig472 thoracic1 #fi ,vertebral column1 #fg ,vertebrata1 #ee ,vesuvius1 #cj ,vicua1 #agh 7fig47 ,virgin ,valley stage1 #abg ,viscaccia1 #ahc 7fig471 #ahe ,viverravus1 #eee1 #eeh ,viverrid1 #eah1 #eec1 #eed1 #eeh ,viverrines1 see ,viverrid ,viviparous mammals1 #ei ,vizcacha1 #ahc 7fig471 #ahe ,vizcachas1 ,pleistocene1 #bah ,volcanic ash1 #bi2 ,bridger1 #aaj1 #aae2 ,john ,day1 #aaf2 ,santa ,cruz1 #abd2 ,white ,river1 #aae ,volcanic dust1 #bi ,volcanic material1 #f2 ,florissant1 #aba2 ,miocene1 #aah2 ,pliocene1 #abe ,volcanoes1 #acc ,voles1 #ahb ,,voltaire1 #fdf ,vulcanism1 ,miocene1 #aah1 #aba2 ,pliocene1 #abg ,vulpavus1 #eee1 #eeh ,vulpes1 #adi 7fig471 #aej 7fig471 #aeh 7fig471 #eag ,,waagen1 ,w41 #ffb ,,wallace1 ,a4 ,r41 #acf1 #aci1 #aej1 #agj1 #aga ,walnuts1 #ajb ,walruses1 #a1 #de1 #bjg1 #baj1 #eaf2 ,pleistocene1 #bg1 #acb ,wapiti1 #ej1 #aea1 #aee 7fig471 #aha1 #bjb1 #bjh1 #daa1 #dab1 #dac ,warm ,temperate region1 #afa ,wart ,hog1 #cfc ,wasatch age and stage1 #ag1 #ajf1 #bgc1 #bgd1 #bge1 #bhe1 #caf1 #cbe1 #cgj1 #cih1 #djj1 #dea1 #deb1 #dec1 #dee1 #deg1 #dei1 #efj1 #efa1 #eff1 #efh1 #ega1 #egb1 #ehj1 #eha ,wasatch ,mts41 ,pleistocene glaciers1 #aca ,wasatch-,sparnacian stage1 #aae ,water ,hog1 #ahc 7fig471 #ahe1 #bje1 #baa4 7,see also ,capybara and ,carpincho7 ,weasel1 #eea2 family1 #agd2 ,miocene1 #bch2 ,pleisto41 ,s4 ,amer41 #bac2 tribe1 #eah ,weasels1 #ei1 #aeb1 #eag2 ,miocene1 #bbi1 #bch2 ,pleistocene1 #bjd1 #bje ,,weber1 ,m41 #dbf ,western ,hemisphere1 marsupials1 #fbf ,west ,indian1 islands1 #afd1 #aia2 shells on ,n4 ,j4 coast1 #aac2 subregion1 #agj 7map7 ,west ,indies1 #ehc2 ,eocene1 #aab2 ,oligocene1 #aac2 ,paleocene1 #ajc2 ,pleistocene1 #acd2 zology1 #adf ,whale1 ,right1 #dh ,whales1 #a1 #b1 #c1 #cg1 #de1 #fj1 #gd1 #ddb2 ,miocene1 #abc2 ,pleistocene1 #acb2 toothed1 #fj2 whalebone1 #fj1 #id ,white ,mts41 ,labrador plants of1 #aic ,white ,river age and stage1 #aa1 #ab1 #ag1 #aac1 #bej1 #bff1 #bfg1 #bgj1 #bga1 #bgb1 #cab1 #cbe1 #cbf1 #cdj1 #cda1 #cdf1 #cej1 #ceg1 #cfe-cga1 #cge1 #cgg-chj1 #chb-che1 #cid-cif1 #cii1 #dje1 #djg1 #djh1 #ebc1 #ebh-ecj1 #ece1 #ech-eda1 #edf1 #eeg1 #efb1 #efc1 #efe1 #eff1 #fca2 mammals1 #beb 7restorations7 ,wild-cats1 #ada ,willamette ,valley1 ,miocene1 #aae ,,williston1 ,s4 ,w41 #cc1 #ehi ,willows1 #ajb ,wind ,river age and stage1 #ag1 #aji1 #bgc1 #cae1 #caf1 #cbf1 #cci1 #cej1 #djj1 #dej1 #deb1 #def1 #deg1 #dfj1 #efh1 #ega ,windward ,islands1 ,pleistocene1 #acd ,winter1 destruction of mammals by1 #cf ,wisent1 #aeb ,wolf1 #cb1 #fb 7skull fig471 #fd 7do471 #fi 7dorsal vertebra fig471 #gj 7atlas fig471 #ga 7axis fig471 #gb 7cervical and dorsal vertebr fig471 #gc 7lumbar and caudal fig471 #gd 7ribs fig471 #ge 7ribs and sternum fig471 #gf 7scapula fig471 #gg 7hip-bone fig471 #gh 7humerus fig471 #hj 7fore-arm bones fig471 #hb 7manus fig471 #he 7femur fig471 #hf 7femur and patella fig471 #hg 7leg-bones fig471 #hh 7pes fig471 #ib1 #ic 7dentition fig472 ,fox-like1 #aga 7fig472 ,grey1 #aeb1 #aei 7fig472 ,large-eared1 #fef2 ,miocene1 #ebb 7skull fig472 ,timber1 #aei 7fig471 #afb ,wolverene1 #ada1 #aeb1 #aee 7fig471 #bac1 #bch1 #eag1 #eea2 ,pleistocene1 #bjd ,wolves1 #ei1 #afd1 #agc1 #bdi1 #eag1 #eah1 #ebj1 #ebc1 #ebe1 #ecj2 fox-like1 #agc1 #bab1 #eeb2 ,pleistocene1 #bjd2 ,pliocene1 #bbb2 ,white ,river1 #bed ,wombats1 #fdj ,woodchuck1 #aeb 7fig471 #aec ,wood-rats1 #ada1 #aec1 #afd ,,wortman1 ,j4 ,l41 #chc1 #che1 #cii1 #egj1 #ega ,xotodon1 #dfb ,yapock1 #fca ,yellowstone ,park1 petrified forests1 #abb2 ,miocene lava1 #abb2 ,pliocene lava1 #abg ,young animals1 colour pattern of1 #df ,yucatan1 #abh ,yukon ,valley1 ,miocene1 #aah ,zadyus1 #aij1 #eib ,zapus1 #aec1 #afj 7fig47 ,zebra1 #dd2 bones of1 #ce2 ,burchell's1 #bjj ,zebras1 #bac1 #bib1 #cjh ,zeuglodontia1 #fj ,,zittel1 ,k4 ,,von1 #fja ,zology1 ,experimental1 #fdh1 #ffc ,zygolestes1 #fbg1 #fda ,zygomatic arch1 #fe ,the following pages contain advertisements of books by the same author or on kindred subjects4 ,,the ,,macmillan ,,company ,publishers #fd-ff ,fifth ,avenue ,new ,york ,,by ,,the ,,same ,,author ,an ,introduction to ,geology ,,by ,,william ,b4 ,,scott1 ,,ph4,d41 ,,ll4,d4 ,blair ,professor of ,geology and ,palontology in ,princeton ,university ,new ,york1 #aijg ,new ,edition1 completely revised1 #aijg ,latest ,reprint1 #aiji ,illustrated #abmo #b4fj ,intended to serve as an introduction to the science of ,geology1 both for students who desire to pursue the subject exhaustively and also for those who wish merely to obtain an outline of the methods and principal results of the science4 ,to the future specialist such a preliminary survey of the whole field will afford the necessary orientation4 ,to the non-specialist the graphic presentation of the outlines of the subject cannot fail to prove both interesting and informing4 ,the book aims to cultivate a proper scientific attitude by training the student to carefully distinguish between fact and inference and between observation and hypothesis4 ,he is taught to weigh his evidences carefully1 and while balancing probabilities suspend judgment where the data for decision are insufficient4 ,the new edition incorporates the results of all the important advances made in geological knowledge in recent years4 ,the number of illustrations has been greatly increased1 thus adding to the admirable clearness of the text4 ,guide to the ,study of ,animal ,ecology ,,by ,,charles ,c4 ,,adams ,associate in ,animal ,ecology in the ,university of ,illinois ,cloth1 #abmo #ahc pp4 #a4be net ,this work is the outgrowth of the author's efforts during the last ten years to find some consistent and satisfactory working plan for handling the almost bewildering number of facts of ecological significance which have been accumulating in the literature of zology1 biology1 and the allied sciences4 ,an ecological point of view is described more fully than other subjects1 so that the student may see the need of familiarity with those tests or criteria by means of which he may be able to determine for himself ecological relations and the validity of ecological studies4 ,the other phases are treated less fully in the discussions and with more detail bibliographically1 so that this may be a useful source-book4 ,in fact1 the very extensive and up-to-date bibliography is one of the important features of the entire book4 ,the ,age of ,mammals in ,europe1 ,asia1 and ,north ,america ,,by ,,henry ,,fairfield ,,osborn ,a4,b41 ,,sc4,d4 ,,princeton1 ,,hon4 ,,ll4,d4 ,,trinity1 ,,princeton1 ,,columbia1 ,,hon4 ,d4,,sc4 ,,cambridge ,,university1 ,,hon4 ,,ph4,d4 ,,university ,,of ,,christiania1 ,,president ,,american ,,museum ,,of ,,natural ,,history1 ,,president ,,new ,,york ,,zo,,logical ,,society ,,illustrated ,,by #bcb ,,half-,,tone ,,and ,,other ,,figures1 ,,including ,,numerous ,,maps1 ,,geological ,,sections1 ,,field ,,views1 ,,and ,,reproductions ,,from ,,photographs ,,of ,,mounted ,,fossil ,,skeletons ,,and ,,of ,,the ,,famous ,,restorations ,,by ,,charles ,r4 ,,knight4 ,royal #hvo #d4ej net ,carriage extra 8,the ,age of ,mammals0 is not written for the palontologist only4 ,no zologist interested in mammals1 birds1 fishes1 or reptiles can fail to find it of value4 ,the geologist finds here the clearest exposition that has been given of the succession of geological events in the mammal-bearing continental formations of the ,tertiary and ,quaternary of the ,western ,states4 ,the anthropologist finds in the closing chapter on the ,pleistocene a key to most of the problems which confront him as to the time of man's first appearance4 ,the botanist may refer to it for the succession and evolution of flora4 ,to the general reader it offers the first connected account of the history of life on the earth during the later geological epochs1 a record embodying the very latest results of the active research going on in this direction at the present time4 ,in so far as science has succeeded in piecing together the fragmentary evidence of the rocks1 this volume contains glimpses into the remote past of the continental outlines1 the climate1 vegetation1 and animal life of the epochs preceding the 8,age of ,man40 ,the text is supplemented by a very original and suggestive series of illustrations1 notable among which are numerous half-tone reproductions from the famous restorations of extinct mammals by ,charles ,r4 ,knight1 many of which are published here for the first time4 ,moreover1 there is appended to the volume an invaluable ,classification of the ,mammalia1 which gives not only the systematic position but also the geologic and geographic distribution and the popular names of all the important genera of mammals1 both living and fossil4 ,comments on ,the ,age of ,mammals 8,students of palontology have awaited impatiently the past few years a promised work on extinct mammals by ,professor ,osborn4 ,in his #8,age of ,mammals1' expectations have been more than realized40--,s4 ,w4 ,,williston1 in ,science1 ,feb4 #ag1 #aiaa4 8,dr4 ,h4 ,f4 ,osborn is a great palontologist2 in this book he has gathered together the work of a life-time1 and that work1 besides being original and constructive1 is also critical and selective4 ,the result is a great book40 8,while it is an incomparable text-book1 a work of reference to the student1 and1 no doubt a fruitful field for the controversialist of the future1 it is a work which can be read with interest and satisfaction by the #8genial omnivore1' as ,huxley called him1 the general reader40--,the ,field1 ,jan4 #g1 #aiaa4 8,it is in the best sense a source book1 for it gives at first hand1 from the original material1 the ideas of an acknowledged master in mammalian palontology40 8,it has the clarity and directness of style so welcome1 and rare1 in such a book40--,e4 ,c4 ,,case1 in ,bulletin ,american ,geographical ,society1 ,july1 #aiaa4 8,a book of the utmost value to the student and teacher of mammalian life and likewise to the serious reader40--,american ,journal of ,science1 ,feb41 #aiaa4 8,m4 ,osborn 444 devait s'attacher a nous prsenter le tableau aussi complet et aussi fidle que possible des faunes de ,mammifres fossiles qui se sont succd dans l'hmisphre ,nord pendant l're tertiaire4 ,et j'ai plaisir dire tout de suite qu'il y a parfaitement russi40--,m4 ,,boule1 in ,mouvement ,scientifique1 #aiaa1 p4 #efi4 8,professor ,osborn has produced a book which will appeal to the learned specialist and to the thoughtful general reader as well40 8,the work is well adapted to school and college use1 and is abundantly illustrated40--,education1 ,boston1 ,jan41 #aiaa4 8,one of the most notable books on evolution since the appearance of ,darwin's #8,origin of ,species4'0--,forest and ,stream1 ,dec4 #aj1 #aiaj4 8,nejlep souasn palontolog americk1 ,henry ,fairfield ,osborn1 vydal nedvno s titulem tuto citovanm znamenit psanou a pkn vypravenou knihu o #8vku ssavc4'0--,f4 ,bayer in ,vstnku ,cesk ,akademie csae ,frantika ,josefa pro vdy1 slovenost a umen4--,ronk ,,xx1 #aiaa4 8,written with clearness and vivacity1 most admirably illustrated1 especially by the #8restorations' of ,mr4 ,knight1 and illuminated by maps1 ,professor ,osborn builds1 page after page1 his story-mosaic4444 ,the reader will soon discover that he is a brilliant generalizer1 possessed of material gathered from all around the globe1 fructifying his knowledge by the exercise of a constructive imagination1 and expressing his facts and ideas in a literary style1 clear1 vigorous1 and entertaining40--,the ,literary ,digest1 ,feb4 #d1 #aiaa4 ,the ,cambridge ,natural ,history ,,edited ,,by ,s4 ,f4 ,,harmer1 ,sc4,d41 ,f4,r4,s4 ,fellow of ,king's ,college1 ,cambridge2 formerly ,superintendent of the ,university ,museum of ,zology2 ,keeper of the ,department of ,zology in the ,british ,museum 7,natural ,history7 ,,and ,a4 ,e4 ,,shipley1 ,m4,a41 ,,hon4 ,sc4,d41 ,princeton1 ,f4,r4,s4 ,master and ,fellow of ,christ's ,college1 ,cambridge2 formerly ,reader in ,zology in the ,university2 ,chairman of ,council of ,marine ,biological ,association ,in ,ten ,volumes ,fully ,illustrated ,medium #hvo ,gilt ,tops ,each ,volume1 #d4ge net ,,contents ,,vol4 ,i4 ,protozoa1 by ,m4 ,hartog2 ,porifera1 by ,igerna ,sollas2 ,coelenterata and ,ctenophora1 by ,s4 ,j4 ,hickson2 ,echinodermata1 by ,e4 ,w4 ,mac,bride4 ,,vol4 ,,ii4 ,flatworms and ,mesozoa1 by ,f4 ,w4 ,gamble2 ,nemertines1 by ,l4 ,sheldon2 ,threadworms and ,sagitta1 by ,a4 ,e4 ,shipley2 ,rotifers1 by ,m4 ,hartog2 ,polychaet ,worms1 by ,w4 ,b4 ,benham2 ,earthworms and ,leeches1 by ,f4 ,e4 ,beddard2 ,gephyrea1 etc41 by ,a4 ,e4 ,shipley2 ,polyzoa1 by ,s4 ,f4 ,harmer4 ,,vol4 ,,iii4 ,molluscs1 by ,h4 ,a4 ,cooke2 ,recent ,brachiopods1 by ,a4 ,e4 ,shipley2 ,fossil ,brachiopods1 by ,f4 ,r4 ,c4 ,reed4 ,,vol4 ,,iv4 ,spiders1 ,mites1 ,scorpions1 etc41 by ,c4 ,warburton2 ,trilobites1 etc41 by ,m4 ,laurie2 ,pycnogonids1 by ,d',arcy ,w4 ,thompson2 ,lingulatulid and ,tardigrada1 by ,a4 ,e4 ,shipley2 ,crustacea1 by ,geoffrey ,smith4 ,,vol4 ,v4 ,peripatus1 by ,a4 ,sedgwick2 ,myriopods1 by ,f4 ,g4 ,sinclair2 ,insects1 ,part ,i1 by ,d4 ,sharp4 ,,vol4 ,,vi4 ,insects1 ,part ,,ii1 by ,d4 ,sharp4 ,,vol4 ,,vii4 ,hemichordata1 by ,s4 ,f4 ,harmer2 ,ascidians and ,amphioxus1 by ,w4 ,a4 ,herdman2 ,fishes 7exclusive of systematic account of ,teleostei71 by ,t4 ,w4 ,bridge2 ,fishes 7systematic account of ,peleostei71 by ,g4 ,a4 ,boulanger4 ,,vol4 ,,viii4 ,amphibia and ,reptiles1 by ,hans ,gadow4 ,,vol4 ,,ix4 ,birds1 by ,a4 ,h4 ,evans4 ,,vol4 ,x4 ,mammalia1 by ,f4 ,e4 ,beddard4 ,,what ,,the ,,critics ,,say ,,of ,,the ,,cambridge ,,natural ,,history ,new ,york ,evening ,post4 ,its editors may well be congratulated upon the completion of such an undertaking1 whose vastness and difficulty can be adequately appreciated only by the skilled zologist4 ,the student of biology who turns to this volume 7,vol4 iv7 will not be disappointed in its value as a serviceable handbook4 ,it is pleasant to observe how numerous1 clear1 and satisfactory are the drawings that illustrate the text4 ,american ,journal of ,science4 ,the most convenient and generally useful work of reference on the subject that has appeared in the ,english language in recent years4 ,book ,review ,digest4 ,the zealous student1 anxious to bring his knowledge up to date1 will find here a compendium on which he can rely4 ,field4 ,the ,cambridge ,natural ,history series of volumes is one of very great value to all students of biological science4 ,times4 ,there are very many1 not only among educated people who take an interest in science1 but even among specialists1 who will welcome a work of reasonable compass and handy form containing a trustworthy treatment of the various departments of ,natural ,history by men who are familiar with1 and competent to deal with1 the latest results of scientific research4 ,altogether1 to judge from this first volume1 the ,cambridge ,natural ,history promises to fulfil all the expectations that its prospectus holds out4 ,academy4 ,the editors have aimed very high1 and they have succeeded4444 ,well conceived1 carefully cordinated1 and executed with the greatest detail and completeness1 the ,cambridge ,natural ,history is certain to rank high amongst those gigantic scientific works to which1 within the last half-century or so1 the labours of so many experts1 each without hope of more glory than falls to a mere assistant1 have contributed4 ,athenum4 ,the series certainly ought not to be restricted in its circulation to lecturers and students only2 and1 if the forthcoming volumes reach the standard of the one here under notice1 the success of the enterprise should be assured4 ,science ,gossip4 ,every library1 school1 and college in the country should possess this work1 which is of the highest educational value4 ,daily ,news in a ,review of ,vol4 ,x4 ,a volume which1 for the interest of its contents and for its style and method of treatment1 is not only worthy of its predecessors1 but may be regarded as one of the most successful of a brilliant series4 ,a ,,great ,,explorer',s ,,story ,my ,life ,with the ,eskimo ,,by ,,vilhj,,lmur ,,stef,,nsson ,,illustrated ,,with ,,half-,,tone ,,reproductions ,,of ,,photographs ,,taken ,,by ,,the ,,author ,,and ,,others ,decorated cloth1 #hvo ,a fascinating book of description and adventure has been written by the famous traveler and explorer1 who has passed years of his life within the ,arctic ,circle4 ,mr4 ,stefnsson has had a vast amount of material from which to draw and he has made his selection wisely4 ,he has lived with the ,eskimo for long periods2 he knows their language2 he has subsisted on their food2 he has heard their legends2 he has seen them in their daily lives as have few explorers4 ,consequently his remarks about this primitive and matter-of-fact people are shrewd1 true1 and frequently amusing4 ,the experiences and tales which he recounts1 mirroring the hardships and the inspirations of life in a fearful but wonderful country1 compose a work quite the most absorbing on it that has ever been published4