,,the ,,zoology ,,of ,,the ,,voyage ,,of ,h4 ,m4 ,s4 ,,beagle1 ,,under ,,the ,,command ,,of ,,captain ,,fitzroy1 ,r4,n41 ,,during ,,the ,,years #ahcb ,,to #ahcf4 ,,published ,,with ,,the ,,approval ,,of ,,the ,,lords ,,commissioners ,,of ,,her ,,majesty',s ,,treasury4 ,edited and ,superintended by ,,charles ,,darwin1 ,,esq4 ,m4,a4 ,f4,r4,s4 ,,sec4 ,g4,s4 ,,naturalist ,,to ,,the ,,expedition4 ,,part ,i4 ,,fossil ,,mammalia3 ,,by ,,richard ,,owen1 ,,esq4 ,f4,r4,s4 ,,professor ,,of ,,anatomy ,,and ,,physiology ,,to ,,the ,,royal ,,college ,,of ,,surgeons ,,in ,,london2 ,,corresponding ,,member ,,of ,,the ,,institute ,,of ,,france1 ,,etc4 ,,etc4 ,,london3 ,,published ,,by ,,smith1 ,,elder ,,and ,,co4 #fe1 ,,cornhill4 ,,mdcccxl4 ,,london3 ,,printed ,,by ,,stewart ,,and ,,murray1 ,,old ,,bailey4 ,,contents4 ,page ,,geological ,,introduction #c ,,toxodon ,,platensis1 ,description of ,cranium #af of ,lower ,jaw and ,teeth #bi ,,macrauchenia ,,patachonica1 ,cervical ,vertebr #ce ,lumbar ,vertebr #dj ,scapula #dc ,antibrachium and ,fore-foot #dd ,femur #dh ,tibia1 ,astragalus1 and ,metatarsal ,bone #ej ,,glossotherium1 ,fragment of ,cranium #eg ,,mylodon ,,darwinii1 ,lower ,jaw and ,teeth #fc ,,scelidotherium ,,leptocephalum1 ,cranium and ,teeth #gc ,vertebral ,column #hd ,bones of the ,extremities #hh ,,megalonyx ,,jeffersonii1 ,lower ,jaw #ii ,,megatherium ,,cuvieri1 ,cranium and ,teeth #ajj ,,tesselated ,,armour ,,and ,,bones1 large ,edentata #ajf ,,mastodon ,,angustidens1 ,cuv4 787 #ajh ,,equus1 ,molar ,teeth #ajh ,,ctenomys ,,priscus1 and a large ,rodent #aji ,geological contemporaneity of preceding extinct ,mammalia #aaa ,,list ,,of ,,plates4 ,,plate ,i4 ,cranium of ,toxodon ,platensis1 nat4 size1 basal view1 with the sixth molar1 right side upper jaw1 and grinding surface of the seventh molar left side4 ,,ii4 ,cranium of ,toxodon ,platensis1 side view4 ,,iii4 ,ditto1 upper view4 ,,iv4 ,ditto1 back view1 with two views of the sixth molar1 right side1 upper jaw4 ,v4 ,fragment of lower jaw1 and teeth of ,toxodon ,platensis4 ,,vi4 ,cervical vertebr of the ,macrauchenia ,patachonica4 ,,vii4 ,ditto1 ditto1 and of ,auchenia ,llama4 ,,viii4 ,lumbar vertebr of the ,macrauchenia ,patachonica4 a4 ,medium convex articular surface joining the body of the sacrum4 b4 ,lateral concavities joining the transverse processes of the b4 sacrum4 c4 ,ossified ligament of an anchylosed lumbar vertebra4 ,,ix4 ,fig4 #a and #b4 ,fragments of the ,scapula4 ,fig4 #c4 ,distal end of the femur of ,macrauchenia ,patachonica4 ,x4 ,proximal ends of the anchylosed radius and ulna of ,macrauchenia ,patachonica4 ,,xi4 ,bones of the right fore-foot1 ,macrauchenia ,patachonica4 ,,xii4 ,femur1 ,macrauchenia ,patachonica4 ,,xiii4 ,anchylosed tibia and fibula1 ,macrauchenia ,patachonica4 ,,xiv4 ,right astragalus1 ,macrauchenia ,patachonica4 ,,xv4 ,fig4 #a4 ,external metatarsal bone of the right hind-foot4 ,fig4 #b4 ,proximal end of internal metacarpal bone1 right fore-foot4 ,fig4 #c and #d4 ,proximal end of middle metacarpal bone4 ,fig4 #e4 ,proximal end of external metacarpal bone1 right fore-foot1 ,macrauchenia ,patachonica4 ,,xvi4 ,fragment of cranium of the ,glossotherium4 ,fig4 #a4 ,side view4 ,fig4 #b4 ,base view4 ,fig4 #c4 ,inside view1 all half natural size4 ,fig4 #d4 ,os tympanicum1 natural size4 ,,xvii4 ,fig4 #a4 ,megalonyx ,jeffersonii4 ,fig4 #b4 ,megalonyx laqueatus4 ,fig4 #c and #d4 ,mylodon ,harlani4 ,fig4 #e4 ,mylodon ,darwinii4 ,,xviii4 ,lower jaw of the ,mylodon ,darwinii4 ,,xix4 ,fig4 #a4 ,side view of the lower jaw4 ,fig4 #b and #c4 ,last molar tooth4 ,fig4 #d4 ,front view of the symphysis of the lower jaw1 ,mylodon ,darwinii4 ,,xx4 ,portion of the skeleton of the ,scelidotherium leptocephalum4 ,,xxi4 ,fig4 #a4 ,side view of the cranium4 ,fig4 #b4 ,back view of the cranium4 ,fig4 #c1 #d1 and #e1 anterior molar1 upper jaw ,scelidotherium4 ,,xxii4 ,upper view of the cranium of the ,scelidotherium4 ,,xxiii4 ,fig4 #a4 ,inside view of cranium4 ,fig4 #b4 ,articular surface for the lower jaw4 ,fig4 #c4 ,section of upper jaw and molar teeth4 ,fig4 #d4 ,section of lower jaw and molar teeth1 ,scelidotherium4 ,,xxiv4 ,cervical and anterior dorsal vertebr of4 ,fig4 #a4 ,scelidotherium4 ,fig4 #b4 ,orycteropus4 ,fig4 #c4 ,dasypus4 ,fig4 #d4 ,myrmecophaga jubata2 all one-third nat4 size4 ,,xxv4 ,fig4 #a and #b4 ,humerus1 radius and ulna of ,scelidotherium4 ,fig4 #c4 ,head of humerus4 ,fig4 #d4 ,head of radius4 ,fig4 #e1 #f1 and #g4 ,femur of ,scelidotherium4 ,,xxvi4 ,fig4 #a1 #c1 and #e4 ,astragalus of ,megatherium4 ,fig4 #b1 #d1 and #f4 ,astragalus of ,scelidotherium4 ,,xxvii4 ,fig4 #a and #b4 ,patella and head of tibia of ,scelidotherium4 ,fig4 #c1 #d1 and #e4 ,ungueal phalanx of ,scelidotherium4 ,,xxviii4 ,fig4 #a4 ,astragalus of ,megatherium4 ,fig4 #b4 ,astragalus of ,scelidotherium4 ,fig4 #c-f4 ,astragalus of ,mylodon or ,megalonyx4 ,,xxix4 ,lower jaw of ,megalonyx ,jeffersonii4 ,,xxx4 ,fragment of the ,cranium of ,megatherium ,cuvieri4 ,,xxxi4 ,section of the upper jaw and teeth of the ,megatherium ,cuvieri4 ,,xxxii4 ,fig4 #a4 ,magnified view of structure of molar of ,megatherium4 ,fig4 #b-e4 ,ungueal phalanx and portions of tesselated armour of ,hoplophorus euphractus4 ,fig4 #f-aa4 ,jaws and teeth of ,ctenomys priscus4 ,fig4 #ab4 ,bones of right hind-foot of a ,rodent4 ,fig4 #ac and #ad4 ,fossil tooth of a ,horse4 ,,preface4 ,his ,majesty's ship1 ,beagle1 under the command of ,captain ,fitz,roy1 was commissioned in ,july1 #ahca1 for the purpose of surveying the southern parts of ,america1 and afterwards of circumnavigating the world4 ,in consequence of ,captain ,fitz,roy having expressed a desire that some scientific person should be on board1 and having offered to give up part of his own accommodations1 ,i volunteered my services2 and through the kindness of the hydrographer1 ,captain ,beaufort1 my appointment received the sanction of the ,admiralty4 ,i must here1 as on all other occasions1 take the opportunity of publicly acknowledging with gratitude1 the obligation under which ,i lie to ,captain ,fitz,roy1 and to all the ,officers on board the ,beagle1 for their constant assistance in my scientific pursuits1 and for their uniform kindness to me throughout the voyage4 ,on my return 7,october1 #ahcf7 to ,england1 ,i found myself in possession of a large collection of specimens in various branches of natural history2 but from the great expense necessary to secure their publication1 ,i was without the means of rendering them generally serviceable4 ,the ,presidents of the ,linnean1 ,zoological1 and ,geological ,societies1 having given me their opinion respecting the utility to be derived from publishing these materials1 ,i addressed a letter to the ,right ,honourable the ,chancellor of the ,exchequer 7,t4 ,spring ,rice1 ,esq47 informing him of the circumstances under which ,i hoped that ,i might venture to solicit the aid of ,government4 ,in reply1 ,i received a communication 7as below7 announcing to me that the ,lords of the ,treasury1 from their readiness to promote ,science1 were willing1 under certain conditions1 to give me the most liberal assistance4 8,treasury ,chambers1 ,august #ca1 #ahcg4 8,,sir1 8,it having been represented to the ,lords ,commissioners of ,her ,majesty's ,treasury1 from various quarters1 that great advantage would be derived to the ,science of ,natural ,history1 if arrangements could be made for enabling you to publish1 in a convenient form1 and at a cheap rate1 the result of your labours in that branch of science1 my ,lords will feel themselves justified in giving their sanction to the application of a sum1 not exceeding in the whole one thousand pounds1 in aid of such a publication2 upon the clear and distinct understanding that the ,work should be published1 and the plates engraved1 in such a manner as to be most advantageous to the ,public at large1 upon a plan of arrangement to be previously submitted to1 and sanctioned by the ,board1 after consultation with those persons1 who1 from their attainments in this branch of science1 are the most capable of advising their ,lordships thereupon2 and that the payments on account of the said sum of one thousand pounds are to be made to you from time to time1 on a certificate that such progress has been made in the engravings1 in accordance with the plan previously approved of1 as to justify the issue then applied for4 ,my ,lords have therefore directed me to communicate to you the views they entertain upon this subject2 and to apprize you that they will be prepared to act in conformity with their arrangement1 upon learning from you that you are ready to proceed with the ,work upon the principles above laid down1 and upon receiving from you a statement of the manner in which you think the ,work should be published1 and the plates engraved1 so as most effectually to accomplish the object my ,lords have in view1 in sanctioning the payment from the ,public ,funds1 in aid of the expenses of the ,work in question4 8,i remain1 8,sir1 ,your ,obedient ,servant1 8,a4 ,y4 ,,spearman40 ,the object of the present ,work is to give descriptions and figures of undescribed and imperfectly known animals1 both fossil and recent1 together with some account1 in the one case1 of their geological position1 and in the other of their habits and ranges4 ,as ,i do not possess the knowledge requisite for such an undertaking1 and as ,i am1 moreover1 particularly engaged in preparing an account of the geological observations1 made during the voyage1 several gentlemen have most kindly undertaken different portions of the ,work4 ,besides the very great advantage insured in thus enlisting the attainments of these ,naturalists in the several departments of science1 to which they have paid most attention1 a great delay is avoided by adopting this method of publication1 which must otherwise have been incurred before the materials could have been made known4 ,an ,account of the ,voyage1 drawn up by ,captain ,fitz,roy1 7and to which ,i have added a volume7 being on the point of publication1 ,i shall not in this ,work enter on any minute details respecting the countries which were visited1 but shall merely give a sketch of the geology in the introduction to the part containing ,fossil ,mammalia1 and a brief geographical notice in that attached to the account of existing animals4 ,at the conclusion of this ,work1 ,i shall endeavour to place together the leading results in the natural history of the different countries1 from which the collections were procured4 ,i may here state that ,mr4 ,owen has undertaken the description of the ,fossil ,mammalia2 ,mr4 ,waterhouse1 the ,recent ,mammalia2 ,mr4 ,gould1 the ,birds2 ,mr4 ,bell1 the ,reptiles2 and the ,rev4 ,l4 ,jenyns1 the ,fish4 ,whatever assistance ,i may obtain in the invertebrate classes1 will be noticed in their respective places4 ,the specimens have been presented to the various public museums1 in which it was thought they would be of most general service3 mention will be made in each part where the objects described have been deposited4 ,,fossil ,,mammalia1 ,described by ,,richard ,,owen1 ,,esq4 ,f4,r4,s4 ,f4,g4,s4 ,f4,l4,s4 ,,professor ,,of ,,anatomy ,,and ,,physiology ,,to ,,the ,,royal ,,college ,,of ,,surgeons ,,in ,,london2 ,,corresponding ,,member ,,of ,,the ,,royal ,,academy ,,of ,,sciences ,,of ,,berlin2 ,,of ,,the ,,royal ,,academy ,,of ,,medicine1 ,,and ,,philomathic ,,society ,,of ,,paris2 ,,of ,,the ,,academy ,,of ,,sciences ,,of ,,philadelphia1 ,,moscow1 ,,erlangen4 ,,with ,a ,,geological ,,introduction1 ,,by ,,charles ,,darwin1 ,,esq4 ,m4,a4 ,f4,g4,s4 c4 c4 ,,corresponding ,,member ,,of ,,the ,,zoological ,,society4 ,,geological ,,introduction4 ,,by ,,mr4 ,,darwin4 ,mr4 ,owen having undertaken the description of the fossil remains of the ,mammalia1 which were collected during the voyage of the ,beagle1 and which are now deposited in the ,museum of the ,college of ,surgeons in ,london1 it remains for me briefly to state the circumstances under which they were discovered4 ,as it would require a lengthened discussion to enter fully on the geological history of the deposits in which these remains have been preserved1 and as this will be the subject of a separate work1 ,i shall here only give sufficient details1 for the reader to form some general idea of the epoch1 at which these animals lived1--of their relative antiquity one to the other1--and of the circumstances under which their skeletons were embedded4 ,all the remains were found between latitudes #ca and #ej on the eastern side of ,south ,america4 ,the localities may conveniently be classed under three divisions1 namely--the ,provinces bordering the ,plata2 ,bahia ,blanca situated near the confines of ,northern ,patagonia2 and ,southern ,patagonia4 ,the first division includes an enormous area1 abounding with the remains of large animals4 ,to the eastward and southward of the great streams1 which unite to form the estuary of the ,plata1 those almost boundless plains extend1 which are known by the name of the ,pampas4 ,their physical constitution does not vary over a wide extent2--the traveller may pass for many hundred miles on a level surface1 without meeting with a single pebble1 or discovering any change in the nature of the soil4 ,the formation consists of a reddish argillaceous earth1 generally containing irregular concretions of a pale brown1 indurated marl4 ,this stone1 where most compact1 is traversed by small linear cavities1 and in several respects resembles the less pure fresh-water limestones of ,europe4 ,the concretions not unfrequently become so numerous1 that they unite and form a continuous stratum1 or even the entire mass4 ,at ,bajada de ,sta4 ,f1 in the ,province of ,entre ,rios1 beds of sand1 limestone1 and clay of different qualities1 containing sharks' teeth and sea-shells1 underlie the ,pampas deposit4 ,the shells1 although numerous1 are few in kind4 ,mr4 ,george ,b4 ,sowerby informs me that they appear to belong to one of the less ancient tertiary epochs2 they consist of ,venus nov4 spec4 near to ,v4 cancellata2 ,arca nov4 spec4 near to ,a4 antiquata2 a very large oyster1 probably an extinct species2 an imperfect specimen of a second species of oyster near to ,o4 edulis2 and a ,pecten near to ,p4 opercularis4 ,these beds pass upwards into an indurated marl1 and this again into the red argillaceous earth of the ,pampas1 containing the remains of those extinct quadrupeds1 which every where characterize that deposit4 ,to the southward of the ,plata level plains of an uniform composition1 interrupted only at wide intervals by hills of crystalline rock1 extend to a distance of about three hundred miles2 and to the northward for at least an equal space1 and probably much further4 ,as might have been expected from the perfectly level surface1 wherever a continuous section is presented on the banks of the great rivers1 very slight changes of colour show1 that the deposit has been accumulated in strata as horizontal as the land1 or as the water-line at the base of the cliffs4 ,in the province of ,banda ,oriental 7to the ,n4 and ,n4 ,e4 of the ,plata71 and in part of that of ,entre ,rios1 the land1 though very low and level1 has a foundation of granitic and other primary rocks4 ,these older formations are partially covered1 in most parts1 by a reddish earthy mass containing a few small calcareous concretions2 while in other parts1 they are concealed by more regular strata1 of indurated marl passing into limestone1 of conglomerates1 and ferruginous sandstone4 ,the entire formation probably belongs to the same epoch with that of the ,pampas deposit4 ,in the earthy mass1 even where it is of little thickness1 and where it might readily be mistaken for detritus produced from the underlying granites1 remains of large quadrupeds have several times been discovered4 ,on the shores of the ,plata and in the neighbouring districts1 proofs of a change of level having taken place between the land and the water within a recent period1 may be observed4 ,both near ,monte ,video and ,colonia del ,sacramiento1 beds of shells are lying on the beach at the height of several feet above the present tidal action4 ,near ,maldonado ,i saw estuary shells of recent species embedded in clay1 and raised above the level of a neighbouring fresh-water lake4 ,on the banks of the ,parana1 a shell identical with1 or most closely resembling an estuary species 7,potamomya labiata1 now living in that part of the ,plata1 where the water is brackish7 is accumulated in great masses1 which are found some miles inland1 and are elevated several yards above the level of the river4 ,sir ,woodbine ,parish1 also1 has in his possession1 shells procured from an extensive formation near ,ensenada de ,barragan 7south of ,buenos ,ayres71 which is quarried for lime4 ,mr4 ,george ,sowerby has examined these fossils1 and says the following are identical with living kinds2 ,voluta colocynthis1 ,dillwyn3 ,v4 angulata1 ,swainson3 ,buccinum globulosum1 ,kiener3 a variety of ,oliva patula3 a ,cythera closely resembling or identical with ,c4 flexuosa1 and a fragment of a second species1 probably ,c4 purpurascens2 ,potamomya labiata2 and fragments of oysters4 ,there is1 however1 a species of ,mactra in very great numbers1 with which ,mr4 ,sowerby is wholly unacquainted4 ,i may observe that ,i found recent shells of the first five species inhabiting the coast1 a short distance to the southward4 ,some shelly limestone from the same place1 which ,sir ,woodbine ,parish had the kindness to show me1 resembles that which ,i saw at ,bajada1 and in ,banda ,oriental4 ,these beds1 therefore1 probably form parts of the ,pampas deposit1 and are not merely indicative of the period of its elevation4 ,nevertheless1 on the opposite shores of the ,plata1 near the mouth of the ,uruguay1 ,i found lines of sand dunes1 where the ,mactra and ,cythera flexuosa were lying in such quantities on the bare surface1 that the inhabitants1 by merely sifting the sand1 collect them for burning into lime4 ,after these facts we may feel certain1 that at a period not very remote1 a great bay occupied the area both of the ,pampas and of the lower parts of ,banda ,oriental4 ,into this bay the rivers which are now united in the one great stream of the ,plata1 must formerly have carried down 7as happens at the present day7 the carcasses of the animals1 inhabiting the surrounding countries2 and their skeletons would thus become entombed in the estuary mud which was then tranquilly accumulating4 ,nothing less than a long succession of such accidents can account for the vast number of remains now found buried4 ,as their exposure has invariably been due to the intersection of the plain by the banks of some stream1 it is not making an extravagant assertion1 to say1 that any line whatever drawn across the ,pampas would probably cross the skeleton of some extinct animal4 ,at ,bajada1 a passage1 as ,i have stated1 may be traced upwards from the beds containing marine shells1 to the estuary mud with the bones of land animals4 ,in another locality a bed of the same mineralogical nature with the ,pampas deposit1 underlies clay containing large oysters and other shells1 apparently the same with those at ,bajada4 ,we may1 therefore1 conclude that at the period when the ,arca1 ,venus1 and ,oyster were living1 the physical condition of the surrounding country was nearly the same1 as at the time when the remains of the mammalia were embedded2 and therefore that these shells and the extinct quadrupeds probably either co-existed1 or that the interval between their respective existences was1 in a geological point of view1 extremely short4 ,in this part of ,south ,america there is reason to believe that the movements of the land have been so regular1 that the period of its elevation may be taken as an element in considering the age of any deposit4 ,the circumstance1 therefore1 that the beds immediately bordering the ,plata1 contain very nearly the same species of molluscs1 with those now existing in the neighbouring sea1 harmonizes perfectly with the more ancient 7though really modern7 tertiary character of the fossils underlying the ,pampas deposit at ,bajada1 situated at a greater height1 and at a considerable distance in the interior4 ,i feel little doubt that the final extinction of the several large quadrupeds of ,la ,plata did not take place1 until the time when the sea was peopled with all1 or nearly all1 its present inhabitants4 ,bahia ,blanca1 situated in latitude #ci1 and about #bej miles south of the ,plata1 constitutes the second district1 in which ,i found the remains of quadrupeds4 ,this large bay is nearly surrounded by very low land1 on which successive lines of sand dunes mark in many parts the retreat of the water4 ,at some distance inland a formation of highly indurated marl1 passing into limestone1 forms an escarpment4 ,beyond this1 rocks of the same character extend over a wide and desolate plain1 which rises towards the flanks of the distant mountain of the ,sierra de la ,ventana1 composed of quartz4 ,on the low shores of this bay1 only two places occur1 where any section of the strata can be seen2 and at both of these ,i found fossil remains4 ,at ,monte ,hermoso1 a line of cliff of about #abj feet in height1 consists in the upper part of a stratum of soft sandstone with quartz pebbles2 and in the lower of a red argillaceous earth1 containing concretions of pale indurated marl4 ,this lower bed has the same mineralogical character with the ,pampas deposit2 and possibly may be connected with it4 ,the embedded bones were blackened1 and had undergone more chemical change than in any other locality1 which ,i examined4 ,with the exception of a few large scattered bones1 the remains seemed to belong chiefly to very small quadrupeds4 ,in another part of the bay1 called ,punta ,alta1 about eighteen miles from ,monte ,hermoso1 a very small extent of cliff1 about twenty feet high1 is exposed4 ,the lower bed seen at ebb tide1 extends over a considerable area2 it consists of a mass of quartz shingle1 irregularly stratified1 and divided by curved layers of indurated clay4 ,the pebbles are cemented together by calcareous matter1 which results1 perhaps1 from the partial decomposition of numerous embedded shells4 ,in this gravel the remains of several gigantic animals were extraordinarily numerous4 ,the cliff1 in the part above high-water mark1 is chiefly composed of a reddish indurated argillaceous earth2 which either passes into1 or is replaced by1 the same kind of gravel1 as that on which the whole rests4 ,the earthy substance is coarser than that at ,monte ,hermoso1 and does not contain calcareous concretions4 ,i found in it a very few fragments of shells1 and part of the remains of one quadruped4 ,from the bones in one of the skeletons1 and likewise from those in part of another1 being embedded in their proper relative positions1 the carcasses of the animals1 when they perished1 were probably drifted to this spot in an entire state4 ,the gravel1 from its stratification and general appearance1 exactly resembles that which is every day accumulating in banks1 where either tides or currents meet2 and the embedded shells are of littoral species4 ,but from the skeleton1 in one instance1 being in a position nearly undisturbed1 and from the abundance of serpul and encrusting corallines adhering to some of the bones1 the water1 at the time of their burial1 must have been deeper than at present4 ,this conclusion might also have been inferred from the fact1 that in the neighbouring cliff the same bed1 with its shells1 has been uplifted some yards above high-water mark4 ,on the coast to the southward abundant proofs occur1 of a recent elevation of the continent4 ,in the gravel1 nearly all the pebbles are of quartz1 and have originally proceeded from the lofty range of the ,ventana1 distant between forty and fifty miles4 ,besides the pebbles of quartz1 there are a few irregular masses of the same indurated marl1 of which the escarpment of the neighbouring great plain is composed4 ,hence the gravel beds must have been deposited1 when the plain existed as dry land2 and on it probably those great animals once lived1 of which we now find only the remains4 ,the indurated marl forming the plain1 is the same kind of rock with that occurring over a wide extent of the ,pampas2 and there is no reason to doubt1 they are parts of one great formation4 ,nevertheless1 the gravel bed of ,bahia ,blanca1 although subsequent to the calcareous formation1 may be of the same age with those parts of the ,pampas1 which stand at a low level near the ,plata4 ,for on this whole line of coast1 ,i believe1 as the land has continued rising1 fresh littoral deposits have been formed2 and each of these would often owe part of its materials to the degradation of the one last elevated4 ,with respect to the relative age of the ,monte ,hermoso and ,punta ,alta beds1 it is not possible to speak decidedly4 ,a certain degree of similarity in the nature of the strata containing quartz pebbles1 and those of the reddish indurated earth2 and the short distance between the two localities1 would indicate that no long interval had intervened4 ,the beds at ,monte ,hermoso1 certainly were deposited more tranquilly1 and probably in a deeper sea2 so that even skeletons of animals1 no larger than rats1 have been perfectly preserved there4 ,in some parts of the surrounding country1 obscure traces of a succession of step-formed terraces may be observed2 and each of these indicates a period of repose during the elevation of the land1 at which time the strata previously existing were worn away1 and fresh matter deposited4 ,the ,monte ,hermoso beds were1 perhaps1 formed during one such interval1 anterior to the accumulation of the shingle bank at ,punta ,alta4 ,mr4 ,g4 ,sowerby1 who has been good enough to examine the shells which were found with the remains of the quadrupeds1 has given me the following list4 #a4 ,voluta angulata4 #b4 ---- colocynthis4 #c4 ,oliva ,brasiliensis4 #d4 ---- ,nearly related to ,o4 patula1 but specimen imperfect4 #e4 ---- ,nearly related to ,o4 oryza2 less nearly to small species now living at ,bahia ,blanca4 #f4 ---- ,nov4 spec4 #g4 ,buccinum cochlidium4 #h4 ---- globulosum4 #i4 ---- ,one or two minute species1 perhaps young specimens1--unknown4 #aj4 ,trochus ,nov4 spec4 787 same as one now living in the bay4 #aa4 ---- ,nov4 spec4 787 nearly related to last2 differs in not being granular on the surface4 #ab4 ,assiminia 787 ,minute species1 identical with one living in the bay4 #ac4 ,bulinus nucleus4 #ad4 ,fissurella ,probably same as a kind 7nov4 spec4 87 living in the bay4 #ae4 ,crepidula muricata4 #af4 ---- ,nov4 spec4 #ag4 ,cythera ,closely related to1 or identical with ,c4 purpurascens4 #ah4 ,modiola ,same as recent kind 7nov4 spec47 living in the bay4 #ai4 ,nucula ,near to ,n4 margaritacea4 #bj4 ,corbula ,minute species1 unknown4 #ba4 ,cardita ,ditto ditto #bb4 ,pecten ,nov4 spec4 787 very imperfect specimen4 #bc4 ,ostrea ,oysters of the same size now live in the bay4 ,i may add that a fossil encrusting coralline is the same with one now living in the bay4 ,of these shells it is almost certain that twelve species 7and the coralline7 are absolutely identical with existing species2 and that four more are perhaps so2 the doubt partly arising from the imperfect condition of the specimens4 ,of the seven remaining ones1 four are minute1 and one extremely imperfect4 ,if ,i had not made a collection 7far from perfect7 of the shells now inhabiting ,bahia ,blanca1 ,mr4 ,sowerby would not have known as living kinds1 five out of the twelve fossils3 therefore1 it is probable1 if more attention had been paid to collecting the small living species1 some of the seven unknown ones would also have been found in that state4 ,the twelve first shells1 as well as the four doubtful ones1 are not only existing species1 but nearly all of them inhabit this same bay1 on the shores of which they are likewise found fossil4 ,moreover1 at the time1 ,i particularly noticed that the proportional numbers appeared closely similar between the different kinds1--in those now cast up on the beach1 and in those embedded with the fossil bones4 ,under these circumstances1 ,i think1 we are justified 7although some of the shells are at present unknown to conchologists7 in considering the shingle strata at ,punta ,alta1 as belonging to an extremely modern epoch4 ,from the principle already adduced1 namely1 the regular and gradual elevation of this part of the continent1 ,i should have judged from the small altitude of the beds at ,punta ,alta1 that the formation had not been very ancient4 ,the conclusion here arrived at1 concerning the age of these fossil mammalia1 is nearly the same1 with that1 inferred respecting those entombed in the ,pampas2 and it will hereafter be shown1 that some of the species are common to the two districts4 ,we may suppose1 that whilst the ancient rivers of the ,plata occasionally carried down the carcasses of animals existing in that country1 and deposited them in the mud of the estuary2 other animals inhabited the plains round the ,sierra de la ,ventana1 and that lesser streams1 acting together with the currents of a large bay1 drifted their remains towards a point1 where sand and shingle were accumulating into a shoal4 ,the whole area has since been elevated3 the estuary mud of the former rivers has been converted into wide and level plains2 and the shoals of the ancient ,bahia ,blanca now form low headlands on the present coast4 ,the third locality1 which ,i have to specify1 is ,port ,st4 ,julian1 in latitude #di #ae on the coast of ,southern ,patagonia4 ,the tertiary plains of that country are modelled into a succession of broad and level terraces1 which abut one above the other2 and where they approach the coast1 are generally cut off by a line of precipitous cliff4 ,the whole surface is thickly covered by a bed of gravel1 composed of various kinds of porphyries1 and probably originating from rocks situated within the ,cordillera4 ,the lower part of the formation consists of several varieties of sandstone1 and contains many fossil shells1 the greater number of which are not found in a living state4 ,the south side of ,port ,st4 ,julian is formed by a spit of flat land1 of nearly a hundred feet in height2 and on its surface existing species of littoral shells are abundantly scattered4 ,the gravel is there covered 7a circumstance which ,i did not observe in scarcely any other locality7 by a thin but irregular bed of a sandy or loamy soil1 which likewise fills up hollows or channels worn through it4 ,in the largest of these channels the remains of the single fossil quadruped1 which was here discovered1 were embedded4 ,the skeleton probably was at first perfect2 but the sea having washed away part of the cliff1 has removed many of the bones1--the remaining ones1 however1 still occupying their proper relative position to each other4 ,i am inclined to attribute the origin of this earthy matter1 to the mud which might have accumulated in channels1 and on the surface of the gravel1 if this part of the plain had formerly existed as a harbour1 such as ,port ,st4 ,julian is at the present day4 ,the ,guanaco1 the only large animal now inhabiting the wild plains of ,patagonia1 often wanders over the extensive flats1 which are left dry at the head of the harbour during ebb tide3 we may imagine that the fossil animal1 whilst in a like manner crossing the ancient bay1 fell into one of the muddy creeks1 and was there buried4 ,i have stated that existing species of shells are scattered over the surface of this plain2 namely1 ,mytilus ,magellanicus2 a second and undescribed species1 now living on the beach2 ,m4 edulis2 ,patella deaurata2 and on another part of the coast1 but having similar geological relations1 ,fusus ,magellanicus2 ,voluta ancilla2 and a ,balanus3--these shells are among the commonest now living on this coast4 ,although they must have been lying exposed to the atmospheric changes for a very long period1 they still partially retain their different colours4 ,from these facts we know1 with certainty1 that the superficial deposit1 containing the remains of the quadruped1 has been elevated above the sea1 within the recent period4 ,from the structure of the step-like plains1 which front the coast1 it is certain that each step must have been modelled1 subsequently to the elevation of the one standing above it2 and1 as the same recent shells occur on two higher plains1 we may1 with safety1 conclude1 that the earthy matter1 forming the surface of this lower one1 together with its embedded skeleton1 was deposited long after the existence of the present species1 still inhabitants of the sea4 ,according1 therefore1 to the chronology1 taken from the duration of species among the molluscs1 the fossil quadruped of ,port ,st4 ,julian must have been coeval1 or nearly so1 with those from ,bahia ,blanca4 ,having now briefly described the principal circumstances in the geology of the three districts1 to which ,i at first alluded1 ,i will conclude1 by observing1 that the fossil mammalia of ,la ,plata1 ,bahia ,blanca1 and ,port ,st4 ,julian1 must all have lived during a very modern period in the geological history of the world4 ,it is not the proper place in this work to enter on any speculations1 concerning the cause of the extinction of so many gigantic animals4 ,i will only here add1 that there is the strongest evidence against admitting the theory of a period of overwhelming violence1 by which the inhabitants of the land could have been swept away1 and destroyed4 ,on the contrary every thing indicates a former state of tranquillity1 during which various deposits were accumulating near the then existing coasts1 in the same manner1 as we may suppose others are at this day in progress4 ,the only physical change1 which we know has taken place1 since the existence of these ancient mammalia1 has been a small and gradual rising of the continent2 but it is difficult to believe1 that this alone could have so greatly modified the climate1 as to have been the cause of the utter extermination of so many animals4 ,mr4 ,owen will mention the exact locality where the remains of each quadruped were discovered2 and1 at the conclusion1 it will be easy to specify by name those1 which1 from being embedded in the same deposit1 are known formerly to have co-existed on the continent of ,south ,america4 ,,fossil ,,mammalia4 ,,by ,,mr4 ,,owen4 ,it may be expected that the description of the osseous remains of extinct ,mammalia1 which rank amongst the most interesting results of ,mr4 ,darwin's researches in ,south ,america1 should be preceded by some account of the fossil mammiferous animals which have been previously discovered in that ,continent4 ,the results of such a retrospect are1 however1 necessarily comprised in a very brief statement2 for the ,south ,american relics of extinct ,mammalia1 hitherto described1 are limited1 so far as ,i know1 to three species of ,mastodon1 and the gigantic ,megatherium4 ,one of the above species of ,mastodon 7,mast4 ,cordillerarum7 was established by ,cuvier#a on remains discovered by ,humboldt1 in ,quito1 near the volcanic mountain1 called ,imbaburra1 at an elevation of #abjj toises above the level of the sea2 and likewise at the ,cordilleras of ,chiquitos1 near ,santa ,cruz de la ,sierra1 a locality which is near the centre of ,south ,america4 ,a second species 7,mastodon ,humboldtii1 ,cuv4#b7 is indicated by molar teeth1 stated to have been discovered by the same philosophic traveller1 in ,chile1 near the city of ,concepcion4 ,the third species of ,mastodon appears to have once ranged in vast troops over the wide empire of ,peru3 numerous teeth were brought thence to ,paris by ,dombey1#c and similar teeth1 together with a humerus and tibia from ,santa ,f de ,bogota were placed by ,humboldt at the disposal of ,cuvier1#d who considered them to belong to the ,mastodon angustidens1 a species of which the fossil remains are by no means uncommon in several localities of ,europe4 ,cuvier is also disposed to refer to the same species the teeth of the ,mastodon from ,brazil and ,lima1 mentioned by ,dr4 ,w4 ,hunter in his observations on the animal incognitum from the ,ohio4#e ,the ,megatherium has been scientifically described and illustrated in the works of ,bru1 ,cuvier1 and ,d',alton1 whose accounts are founded on a nearly complete skeleton of this stupendous quadruped which has existed in the ,royal ,museum at ,madrid for more than half a century4 ,the few deficiencies in its osteography have recently been supplied by the descriptions and figures given by ,dr4 ,buckland#f and ,mr4 ,clift1#g taken from remains of the ,megatherium1 brought by ,sir ,woodbine ,parish from ,buenos ,ayres1 and which were discovered in the bed of the ,rio ,salado1 a tributary of the ,rio ,plata4 ,sir ,woodbine ,parish's collection from the same locality1 includes also remains of other species of extinct ,edentata1 which have not yet been described4 ,m4 ,d',orbigny1 in his travels in ,south ,america 7vol4 i4 p4 #if471 states that1 in the banks of the ,parana1 he found the fossil remains of a large quadruped1 of the size of an ,ox1--another quadruped of the size of a ,cat1 apparently of the carnivorous order2--and a third1 a ,rodent as large as a ,rat4 ,this meagre condition of the historical part of the subject of ,south ,american fossils by no means arises from their actual scarcity4 ,the writings of some of the old ,spanish authors1 for instance1 ,torrubia1 ,garcillasso1 and others1#h contain frequent allusions to the bones of giants1 who in times of old dwelt in ,peru4 ,legentil1 also1 in #agbh1 speaks as an eye-witness of these ,peruvian remains2 and his guides pointed out to him the traces of the thunder-bolts1 by which the ,anaks of the ,new ,world had been exterminated4 ,bones and teeth of the ,mastodon are1 according to ,humboldt1 so abundant in a locality near ,santa ,f de ,bogota in ,columbia1 that to this day it bears the name of the 8,field of ,giants40 ,but independently of these indications1 the abundance and variety of the osseous remains of extinct ,mammalia in ,south ,america are amply attested by the materials for the following descriptions1 collected by one individual1 whose sphere of observation was limited to a comparatively small part of ,south ,america2 and the future traveller may fairly hope for similar success1 if he bring to the search the same zeal and tact which distinguish the gentleman to whom ,oryctological ,science is indebted for such novel and valuable accessions4 ,it is remarkable that all the fossils1 collected by ,mr4 ,darwin1 belong to herbivorous species of mammalia1 generally of large size4 ,the greater part are referrible to the order which ,cuvier has called ,edentata1 and belong to that subdivision of the order 7,dasypodid7 which is characterized by having perfect and sometimes complex molar teeth1 and an external osseous and tesselated coat of mail4 ,the ,megatherium is the giant of this tribe2 which1 at the present day1 is exclusively represented by ,south ,american species1 the largest 7,dasypus ,gigas1 ,cuv47 not exceeding the size of a ,hog4 ,the hiatus between this living species and the ,megatherium1 is filled up by a series of ,armadillo-like animals1 indicated more or less satisfactorily by ,mr4 ,darwin's fossils1 some of which species were as large as an ,ox1 others about the size of the ,american ,tapir4 ,the rest of the collection belongs1 with the exception of some small ,rodents1 to the extensive and heterogeneous order ,pachydermata2 it includes the remains of a ,mastodon1 of a ,horse1 and of two large and singular aberrant forms1 one of which connects the ,pachydermatous with the ,ruminant ,order2 the other1 with which the descriptions in the following pages commence1 manifests a close affinity to the ,rodent ,order4 ,a ,,description ,,of ,,the ,,cranium ,,of ,,toxodon ,,platensis2 ,a gigantic extinct mammiferous animal1 referrible to the ,order ,pachydermata1 but with affinities to the ,rodentia1 ,edentata1 and ,herbivorous ,cetacea4 ,the cranium1 which is the subject of the present description1 was found in the ,sarandis1 a small stream entering the ,rio ,negro1 and about #abj miles to the ,n4 ,w4 of ,monte ,video3 it had been originally embedded in a whitish argillaceous earth1 and was discovered lying in the bed of the rivulet1 after a sudden flood had washed down part of the bank4 ,the zoological characters deducible from this cranium1 forbid its association1 generically1 with any known ,mammiferous animal1 and it must therefore be referred to an extinct genus1 which ,i propose to call ,toxodon1#i from the curved or arched form of the teeth1 as will afterwards be described4 ,the specific name1 in the absence of other means of knowing the peculiarities of the animal than those afforded by the skull1 may be most conveniently taken from the district 7,la ,plata71 in which its remains were first discovered4 ,the dimensions of the cranium of the ,toxodon ,platensis amply attest that the animal to which it belonged was of a magnitude attained by few terrestrial quadrupeds1 and only to be compared1 in this respect1 with the larger ,pachyderms1 or the extinct ,megatherium4 ,the length of the skull 7of which a base view of the natural size is given in ,plate ,i47 is two feet four inches3 the extreme breadth one foot four inches4 ,the other requisite admeasurements are given in the table at the conclusion of this description4 ,the general form of the skull1 as seen from above1 is pyriform2 but viewed sideways1 and without the lower jaw1 it is semi-ovate2 it is depressed1 elongate1 of considerable breadth1 including the span of the zygomatic arches1 but becoming rather suddenly contracted anterior to them1 the facial part thence growing narrower to near the muzzle1 which again slightly expands4 ,among the first peculiarities which strike the observer1 is the aspect of the plane of the occipital foramen1 and of the occipital or posterior region of the cranium1 the latter of which inclines from below upwards and forwards at an angle of #ej with the basal line of the skull4 ,this slope of the back part of the skull is one of the characteristics of the ,dinotherium2 it is common to all the ,cetacea1 and is met with in a slighter degree in many ,rodentia1 and in the great ,ant-eater and some others of the ,edentate order4 ,the corresponding aspect of the foramen magnum presents nearly the opposite extreme to man in the occipital scale1 proposed by ,daubenton to determine the diversities of the form of the cranium1 as a gage of the intelligence of different animals#aj2 and the indication of the limited capacity of the ,toxodon1 thus afforded1 is strengthened by the very small proportion1 which the bony walls of the cerebral cavity bear to the zygomatic and maxillary parts of the skull1 and to the size of the vertebral column1 as indicated by the condyloid processes1 and foramen magnum4 ,the zygomatic arches are of remarkable size and strength2 they commence immediately anterior to the sides of the occipital plane1 increase in vertical extent as they pass outwards1 forwards and downwards1 and are suddenly contracted as they bend inwards to abut against the sides of the sockets of the two posterior molar teeth4 ,the cranial cavity is remarkably narrow at the space included by the zygomatic arches2 being1 as it were1 excavated on each side to augment the space for the lodgment of the temporal muscles1 so that its diameter at this part is less than that of the anterior extremity of the upper jaw4 ,the upper surface of the cranium expands to form the post-orbital processes1 and again contracts anterior to these4 ,the muscular ridges1 or other characters1 at the top of the skull1 cannot be precisely determined1 as a great proportion of the outer table of the bone is broken away1 exposing a coarse and thick diple4 ,there seems1 however1 to have been a strong ridge separating the occipital from the coronal or upper surface of the cranium4 ,the form of the remaining parts1 which are modified in relation to the attachment of the muscles of the jaws1 indicates that these were powerfully developed both for the offices of mastication and prehension4 ,the general form of the skull1 while it presents certain points of resemblance to that of the aquatic ,pachydermata1 and even of the ,carnivora1 has much that is peculiar to itself2 but1 in the facial part1 it approaches the nearest to that of the ,rodentia2 and the dentition of the ,toxodon1 as exhibited in the upper jaw1 corresponds with that which characterizes the ,rodent ,order4 ,the teeth of the ,toxodon consist of molars and incisors1 separated by a long diastema1 or toothless space4 ,in the upper jaw the molars are fourteen in number1 there being seven on each side2 the incisors four1 one very large1 and one small1 in each intermaxillary bone4 ,the general form and nature of the teeth are indicated by the sockets2 and the structure of the grinders is exhibited in a broken molar1 the last in the series on the left side of the jaw of the present cranium 7,see a figure of the grinding surface restored of this tooth1 fig4 #b1 ,pl4 ,i471 and by another perfect molar1 the last but one on the right side of the upper jaw1 which1 though not belonging to the same individual as the skull here described1 undoubtedly appertains to the same species4 ,this latter tooth 7,fig4 #c1 ,pl4 ,i42 figs4 #b and #c1 ,pl4 ,,iv47 was found by itself1 embedded in the banks of the ,rio ,tercero1 or ,carcarana1 near the ,parana1 at the distance of a hundred and eighty miles from the locality where the head was discovered4 ,fragments of a molar tooth of a ,toxodon1 apparently the seventh of the left side1 upper jaw1 were also found at ,bajada de ,sta ,f1 in the province of ,entre ,rios1 distant forty miles from the mouth of the ,rio ,tercero4 ,all the molar teeth are long and curved1 and without fangs1#aa as in most of the herbivorous species of the ,rodent ,order3 in those1 however1 with curved grinders1 as the ,aperea or ,guinea-pig1 and ,cavia ,patachonica1 the concavity of the upper grinders is directed outward1 the fangs of the teeth of the opposite sides diverging as they ascend in the sockets2 but1 in the ,toxodon1 the convexity of the grinders is outward1 and the fangs converge and almost meet at the middle line of the palate1 forming a series of arches1 capable of overcoming immense resistance from pressure4 7,see the upper view of the skull1 ,plate ,,iii41 in which the fractures expose to view a part of the series of these arched sockets47 ,of the incisors1 the two small ones 7the sockets of which are indicated at s s1 ,pl4 ,,iii47 are situated in the middle of the front of the upper jaw1 close to the suture between the intermaxillaries1 and the two large ones in immediate contiguity with the small incisors1 which they greatly exceed in size4 ,the sockets of the two large incisors 7t t1 ,pl4 ,,iii47 extend backwards1 in an arched form1 preserving a uniform diameter1 as far as the commencement of the alveoli of the molar teeth3 the curve which they describe is the segment of a circle2 the position1 form1 and extent of the sockets of these incisors are the same as in those of the corresponding teeth of the ,rodentia4 ,the matrix1 or secreting pulp of the large incisors1 was lodged1 as in the ,rodentia1 in close proximity with the sockets of the anterior molars2 and we are enabled to infer1 from the form of the incisive sockets1 notwithstanding the absence of the teeth themselves1 that the pulp was persistent1 and that the growth of these incisors1 like those of the ,rodentia1 continued throughout life4 ,this condition1 joined with the form and curvature of the socket1 implies a continual wearing away of the crown of the tooth by attrition against opposing incisors of a corresponding structure in the lower jaw3 and as a corollary1 it may be inferred that the teeth in question had a partial coating of enamel1 to produce a cutting edge1 and were1 in fact1 true dentes scalprarii4 ,the number of incisors in the upper jaw of ,toxodon1 is not without its parallel in the ,rodent ,order1 the genus ,lepus being characterized by four1 instead of two superior incisors1 which also present a similar relative size but have a different relative position1 the small incisors1 in the hare and rabbit1 being so placed immediately behind the large pair1 as to receive the appulse of the single pair of incisors in the lower jaw4 ,in the ,toxodon the position of the incisors1 in the same transverse line1 might lead to the inference1 that they were opposed by a corresponding number in the lower jaw2 but the numerous examples of inequality1 in the number of incisors1 in the upper and lower jaws of existing mammalia1 forbid any conclusion on this point4#ab ,the sockets of the small mesial incisors of the ,toxodon 7s s1 ,pl4 ,,iii47 gradually diminish in size1 as they penetrate the intermaxillary bones1 and we may1 therefore1 infer that the pulp was gradually absorbed in the progress of their development2 and that1 like ordinary incisors1 their growth was of limited duration1 and their lodgment in the jaw effected by a single conical fang4 ,i may observe1 that the formation of a fang is the necessary consequence of the gradual absorption of the matrix or pulp of a tooth2 for the pulp continues1 as it diminishes in size1 to deposit ivory upon the inner surface of the cavity of the tooth from which it is receding1 and the tooth or fang thus likewise progressively diminishes in size4 ,the formation of the socket proceeds uninterruptedly1 and the bone encroaching upon the space left by the tooth1 closely surrounds the wasting fang1 and affords it a firm support2 and thus an inference may be drawn from the form of the socket alone1 as to whether the tooth it contained had or had not one or more conical fangs1 and consequently whether its growth was temporary or uninterrupted4 ,applying this reasoning to the molar teeth of the ,toxodon1 we infer that their growth1 like those of most of the ,phytiphagous ,rodents1 of the ,megatherium and ,armadillo1 was perpetual1 because their sockets are continued of uniform size from the open to the closed extremity2 and the molar tooth which is preserved proves the accuracy of the deduction1 inasmuch as its base is excavated by a large conical cavity for the lodgment of the pulp1 the continued activity of which was the compensation here designed to meet the effects of attrition on the opposite or grinding surface of the tooth4 ,the molar tooth discovered by ,mr4 ,darwin in the banks of the ,tercero1 not only belonged to the same species as the skull under consideration1 but to an individual of the same size2 it fits exactly into the socket next to the posterior one of the right side4 ,the figures subjoined of this molar tooth 7,fig4 #c1 ,pl4 ,i42 figs4 #b and #c1 ,pl4 ,,iv47 almost preclude the necessity of a description4 ,the transverse section of the tooth gives an irregular1 unequal sided1 prism2 the two broadest sides of which converge to the anterior angle1 which is obtusely rounded4 ,the outer surface of the tooth 7fig4 #b1 ,pl4 ,,iv47 is slightly concave in the transverse direction1 but undulating1 from the presence of two slight convex risings which traverse the tooth lengthwise4 ,the inner surface presents at its anterior part a slightly concave surface1 and posteriorly two prominent longitudinal convex ridges1 separated by a groove which is flat at the bottom1 and from the anterior angle of which the reflected fold of enamel penetrates the substance of the tooth1 advancing obliquely forwards1 rather more than half-way across the body of the tooth4 ,a longitudinal ridge of bone projects from the internal side of the socket1 and fits into the groove above mentioned1 and as a corresponding ridge exists in all the sockets of the grinders1 save the two anterior small ones1 we may infer that the five posterior grinders on each side1 had a similar structure to the tooth above described4 ,the external layer of enamel is uniformly about half a line in thickness2 it is interrupted for the extent of nearly three lines at the anterior angle1 and for more than double that extent at the posterior part of the tooth1 which is consequently worn down much below the level of the rest of the grinding surface4 ,where the ivory is thus unprotected by the enamel1 it has a coat of cmentum1 which also fills up the small interval at the origin of the reflected fold of enamel4 ,on the grinding surface of the entire tooth1 and on the fractured ends of the mutilated molars1 the component fibres1 or tubules1 of the ivory1 are readily perceptible by the naked eye1 diverging from the line which indicates the last remains of the cavity of the pulp of the tooth1 as it was progressively obliterated during growth4 ,although the complication of the grinding surface by the inflection of simple or straight folds of enamel is peculiarly characteristic of the ,rodent type1 we must regard the number of molar teeth1 and their diminution of size as they advance towards the anterior part of the jaw1 in the ,toxodon1 as indicative of a deviation from that order1 and an approach to the ,pachyderms4 ,the common number of grinders in the upper jaw of ,rodent animals is eight1 four on each side4 ,in some genera1 as ,lemmus1 ,mus1 ,cricetus1 there are only three on each side1 and in ,hydromys and ,aulacodus1 only two on each side4 ,in ,lepus1 however1 we find six on each side of the upper1 and five on each side of the lower jaw4 ,the ,toxodon1 like the ,tapir and ,hippopotamus1 has seven on each side of the upper jaw3 the first in each of these species being the smallest4 ,it is worthy of notice1 however1 that the ,capybara which adheres to the ,rodent type in the number of its molars1 presents in the vastly increased size1 and additional number of component lamin of the posterior grinders1 an approximation to the pachydermatous character just adduced1 and the bony palate at the same time presents an expansion between these molars1 offering a resemblance to the ,toxodon which ,i have not found in any other ,rodent besides the ,capybara4 ,the most important deviation from the ,rodent structure presented by the teeth1 occurs in the direction of the reflected fold of enamel1 and such a deviation might have been inferred1 even in the absence of the teeth1 from the structure of the articular surface1 or glenoid cavity for the reception of the condyle of the lower jaw4 ,as the ridge of enamel runs1 as above described1 in a direction approaching that of the longitudinal axis of the skull1 it is obvious that the grinding motions of the lower jaw should be in a proportionate degree in the transverse direction4 ,the glenoid cavity1 therefore1 instead of being a longitudinal groove1 and open behind1 as in the true ,rodents1 is extended transversely1 and is defended behind by a broad descending bony process preventing the retraction of the jaw1 and showing marks of the forcible pressure to which it was subject4 ,it is worthy of observation that1 in the ,wombat1--which exhibits the ,rodent type of dentition1 and1 like the ,toxodon1 has remarkably curved molars1 but in an opposite direction1--the condyle of the lower jaw is also extended transversely1 and adapted to an articular surface1 which admits of lateral motion in the trituration of the food4 ,in the outward span of the zygomatic arches1 in which ,toxodon deviates from the ,rodentia1 we may trace a relation of subordinacy to the above structure of the grinding teeth and joint of the lower jaw3 the widening of the arches giving to the masseter muscles greater power of drawing the jaw from side to side4 ,the depth of the zygoma bespeaks the magnitude of these masticatory muscles1 and the included space shews that the temporal muscles were also developed to a degree1 which indicates the force with which the great incisors at the extremity of the jaws1 were used2 probably1 like the canines of the ,hippopotamus1 to divide or tear up by the roots the aquatic plants1 growing on the banks of the streams1 which the ,toxodon may have frequented4 ,in the ,rodentia1 the zygoma1 though sometimes as deep as in the ,toxodon1 is generally almost straight1 and the space included between it and the cranium is consequently narrow4 ,the zygoma also is placed more forwards in all true ,rodents1 than in the ,toxodon2 and1 instead of abutting against the posterior alveoli1 it terminates opposite the anterior ones4 ,it thus affords such an attachment to the masseter1 that this muscle extends obliquely backwards to its insertion in the lower jaw1 at an angle which enables it to act with more advantage in drawing forwards the lower jaw1--a motion for which the joint is expressly adapted4 ,in many ,rodents1 also1 there is a distinct muscle1 or portion of the masseter1 which passes through the ant-orbital foramen1 which is on that account of large size4 ,in examining the cranium of ,toxodon1 with reference to this structure1 it was found that the ant-orbital foramen was not larger than might have been expected to give transmission to nerves requisite for supplying with sensibility the large lips1 and whiskers with which the expanded muzzle of this remarkable quadruped was probably furnished4 ,having thus examined the cranium of the ,toxodon in its relation1 as a mechanical instrument1 subservient to the function of digestion2 we next proceed to consider the structure and composition of those cavities of the skull which gave lodgment and protection to the organs of special sense1 and endeavour to deduce from their structure conclusions as to the degree in which the organs were developed1 and the circumstances under which the senses were exercised4 ,the orbit of ,toxodon forms the anterior boundary of the zygomatic area2 it is about as distinctly defined as in the ,tapir or ,dugong1 having its osseous rim less complete than in the ,hippopotamus1 yet more developed than in the ,capybara1 ,coypus1 and many other ,rodentia1 in which the orbit is scarcely distinguishable in the cranium from the small space occupied by the origin of the temporal muscle4 ,the lower boundary of the orbit in ,toxodon is formed by an excavation in the upper and anterior part of the zygoma2 the upper boundary by a strong and rugged overarching process of the frontal bone1 the posterior angle of which 7a1 ,pl4 ,,iii47 descends a little way1 but leaves a space of three inches and a half between it and the opposite angle of the malar bone below 7b1 ,pl4 ,,ii4 and ,,iii471 the circumference of the orbit being completed probably by ligament in the recent subject4 ,the cavity thus circumscribed is remarkable for the preponderance of the vertical over the transverse or longitudinal diameter1 and indicates great extent of motion of the eyeball in the vertical direction1 such as may be supposed to be well adapted to the exigencies of an amphibious quadruped4 ,the orbit of the ,capybara1 or ,water-hog1 makes a near approach to the form just described4 ,in the elevation of the supra-orbital boundary1 and its outward projection in the ,toxodon1 we perceive an approximation to the form of the orbit in the ,hippopotamus1 but the size of the orbit is relatively larger in the ,toxodon1 which in this respect manifests its affinity to the ,rodentia4 ,in that part of the bony structure of the auditory apparatus1 which is visible on the exterior of the cranium1 the skull of the ,toxodon presents a character in which it recedes from the ,rodentia4 ,in these1 the tympanic portion of the temporal bone is remarkably developed1 forming a large bulla ossea between the glenoid cavity and the occiput2 and it always remains disunited to the other elements of the temporal bone4 ,in the ,toxodon the tympanic bone 7c1 ,pl4 ,,ii47 consists of a rough compressed vertical osseous plate1 wedged in transversely between the occiput and the posterior part of the glenoid cavity4 ,the internal extremity of this plate points inwards and forwards1 representing the styloid process2 behind this is seen the petrous bone1 which forms a small angular protuberance at the basis cranii1 and is less developed than in the ,hippopotamus4 ,anterior to the petrous bone are the orifices of the ,eustachian tube1 and carotid canal2 external to it is the great foramen lacerum1 for the jugular vein and nervus vagus2 and behind it is the anterior condyloid foramen4 ,the foramen auditorium externum is only half an inch in diameter1 and gives passage to a long and somewhat tortuous meatus1 which passes inwards and slightly forwards and downwards2 its direction being precisely the same as in the ,hippopotamus2 it was accompanied1 probably1 by as small an external auricle4 ,but the indications of the aquatic habits of the ,toxodon1 which are presented by the osseous parts relating to the senses of sight and hearing1 are of minor import compared with those afforded by the bony boundary of the nostrils4 ,this boundary circumscribes a large ovate aperture1 the aspect of whose plane is upwards1 and a little forwards1 as in the ,herbivorous ,cetaceans1 and especially the ,manatee 7,trichecus ,manatus1 ,cuv47 ,in one part of the bony structure of the nasal cavity the ,toxodon deviates1 however1 in a marked degree from the ,cetaceous structure2 ,i allude to the frontal sinuses1 which are exposed by the fracture of the upper part of the skull4 7,they are shewn in ,plate ,,iii41 and an asterisk is placed on one of the narrow canals of intercommunication between the sinuses and the nasal passages47 ,the posterior orifice of the nasal cavity is relatively larger and wider than in the ,herbivorous ,cetaceans1 and differs both in form and aspect in consequence of the greater extent of the bony palate4 ,the ,toxodon further differs from the ,manatee and ,dugong1 in the firm nature of the connexion of the bones of the head2 and it differs from the ,hippopotamus in the strong attachment of the intermaxillary bones to the maxillaries4 ,there next remain to be described1 as far as the shattered condition of the skull will permit1 the relative position1 extent1 and connexions of the principal bones composing it4 ,the occipital bone exhibits a complete confluence of its basilar1 condyloid1 and supra-occipital elements4 ,the basilar portion1 in connexion with the corresponding element of the sphenoid bone1 describes a curve whose convexity is downwards4 ,the condyles are large1 extended in the transverse direction1 completely terminal1 and a little inclined downwards below the level of the basilar process4 ,the curve of the articulating surface describes1 in the vertical direction1 two-thirds of a circle1 indicating that the head must have possessed considerable extent of motion upwards and downwards upon the atlas2 thus1 while the body of the ,toxodon was submerged1 the head probably could be raised so as to form an angle with the neck1 and bring the snout to the surface of the water without the necessity of any corresponding inflection of the spine4 ,indeed1 in the form and position of the condyles1 the ,toxodon more nearly resembles the true ,cetacea than any other existing mammalia2 and it is only with these that it can be compared in regard to the aspect of the plane of the occipital foramen1 and of the occipital region of the skull4 ,this is inclined forwards from the occipital foramen at such an angle1 that on viewing the skull from above1 not only the condyles1 but the entire circumference of the occipital foramen are visible4 7,see ,pl4 ,,iii47 ,the upper part of the supra-occipital plate presents a broad rugous depression1 indicative of the insertion of strong cervical muscles1 and probably of a ligamentum ,nuch4#ac ,the ex-occipital processes advance forwards for about an inch beyond the condyles1 and then suddenly extend outwards at right angles to the former line1 and terminate in the form of vertically compressed bony plates2 the lower rugged margins of which represent or perform the office of the mastoid processes 7d1 d1 ,pls4 ,,ii4 and ,,iii474 ,the breadth of the entire occipital region of the skull 7fig4 #a1 ,pl4 ,,iv47 appears to have been1 allowing for the fractures1 about one-third more than the height of the same part4 ,the great development of the tympanic bones in the ,rodentia1 occasions the intervention of a considerable space between the occipital bone and the zygomatic process of the temporal2 but in the great ,toxodon1 in which the sense of hearing was doubtless inferior to that enjoyed by the small and timorous ,rodents1 the tympanic bone is reduced to a thin plate1 which is wedged in between the occiput and glenoid cavity4 ,in this structure1 and the consequent posterior position of the glenoid cavity1 there is a close resemblance between the ,toxodon and the ,hippopotamus1 ,tapir1 and ,rhinoceros4 ,the squamous element of the temporal bone 7,n1 ,pl4 ,,ii47 forms a small proportion of the lateral walls of the cranium1 and also enters into the composition of the lateral and superior parts of the posterior region of the cranium1 where two deep foss perforated by large vascular foramina1 indicate the junction of the squamous bones with the supra-occipital bone4 ,the posterior surface of the skull is thus divided into three broad and shallow depressions1 the two lateral facets being slightly over-lapped by the middle one1 at their junction with it4 ,in this structure the ,toxodon resembles the ,hippopotamus1 and differs considerably from the ,cetacea1 in which the occipital region is rendered convex by the extraordinary development of the brain within4 ,the zygomatic process of the temporal bone projects boldly outwards at its commencement1 where it is of great strength1 and three-sided2 the glenoid cavity extends transversely across the base or inferior surface of this part2 the lateral surfaces converge to form the ridge or upper boundary of the zygoma4 ,the depth of the glenoid cavity is increased by a transverse production of bone both before and behind it3 the posterior process 7g1 ,pl4 ,,ii47 descends the lowest1 and affords the requisite defence against backward dislocation of the lower jaw2 the pressure of the condyle against this process is denoted by a well defined1 transversely-ovate1 flattened and smooth surface1 as if the bone had been planed down at that part3 the anterior transverse boundary is convex and smooth1 and probably formed part of the articulation for the lower jaw4 ,the lower facet of the zygoma anterior to the glenoid cavity gradually contracts in breadth1 as it advances forward1 and at the distance of three inches from the articular cavity the zygoma changes from a prismatic to a laminar form4 ,it is at this point that the zygomatic suture commences1 at the lower margin of the arch2 whence it extends directly forwards for more than half its length1 and then bends upwards at a right angle4 ,the zygomatic suture has a similar course in the ,capybara1 and ,hippopotamus4 ,the remainder of the zygoma is formed externally by the malar bone 7,g ,pl4 ,,ii471 which in its position is intermediate to the ,rodent and ,pachydermatous structures4 ,it is not suspended in the middle of the zygomatic arch1 as in the former order2 neither does it extend into the region of the face so far anterior to the orbit as in the ,tapir or ,hippopotamus4 ,the exterior line of the malo-maxillary suture defines the orbit anteriorly2 but from this line the maxillary bone extends backwards1 along the inner side of the malar portion of the zygoma1 until it almost reaches the temporo-malar suture2 thus abutting by an oblique surface against nearly the whole internal facet of the malar bone1 and materially contributing to the general strength of the zygomatic arch4 ,the malar bone is of considerable vertical extent1 and presents a rugged and thickened inferior margin for the attachment of the masseter4 ,the upper margin of the malar bone is smoothly rounded1 and presents a regular semicircular excavation1 forming the lower boundary of the orbit4 ,the relative magnitude of the zygomata to the entire cranium far exceeds in the ,toxodon that which exists in the ,hippopotamus or any other known ,pachyderm4 ,this arises from the great vertical development of the malar bone behind the orbit1 and the vertical expansion of the temporal portion of the arch4 ,the oblique position of the zygoma1 descending as it advances forwards1 is deserving of attention1 as the ,toxodon1 in deviating from the ,pachyderms in these respects1 makes an evident approach to the herbivorous ,cetaceans1 as the ,dugong and ,manatee3 in the latter ,cetacean we observe a similar development of the lower part of the zygomatic process of the malar bone4 ,it is here1 also1 that we may perceive an indication of a resemblance between the ,megatherium and ,toxodon4 ,there is no discernible trace of the lachrymal bone 7,e1 ,pl4 ,,ii47 having extended1 as in the ,hippopotamus beyond the anterior boundary of the orbit3 the lachrymal foramen is situated rather deep in the orbit1 and the bone itself appears to have been of very small size4 ,the surface of the supra-orbital process of the frontal bone7,c1 ,pl4 ,,ii47 is deserving of attention1 as it presents a peculiar ruggedness which is not found in any other part of the skull2 the irregularity seems1 as it were1 to have been produced by the impression of numerous small tortuous and anastomosing vessels4 ,in the skull of a ,sumatran two-horned ,rhinoceros1 in the ,museum of the ,college of ,surgeons 7,no4 #haf71 the circumference of that part of the surface of the skull which supported the posterior horn1 and which includes precisely the same part of the os frontis1 presents the same character1 the surface being broken by numerous vascular impressions4 ,on the supposition that this character of the supra-orbitary arch in the ,toxodon might indicate the superincumbency of a bony case1 ,i examined the skulls of two ,armadillos1 ,dasypus ,peba and ,das4 #f-;cinctus1 and found that in the ,dasypus #f-;cinctus1 the supra-orbital ridges1 which are slightly elevated1 to support the cephalic plate1 presented1 in a minor degree1 a corresponding rugosity4 ,may we venture then to conjecture that the ,toxodon was defended by an ossified integument like the ,armadillo1 or that it was armed with an epidermic production1 analogous to the horn of the ,rhinoceros2 or had the rugous surface in question as little relation with the parts that covered it as the sculptured surface of the malar bones in the ,cavy8 ,after forming the rugged and prominent supra-orbital processes already described1 the frontal bone continues to send backwards a slightly elevated ridge or crista1 circumscribing the origin of the temporal muscles1 but the extent of this ridge1 and the disposition of the inter-orbital portion of the frontal bones cannot be determined in the present mutilated specimen4 ,the fractures it has sustained are not1 however1 wholly unattended with advantage2 they expose the structure of the diplo1 which from its coarseness of texture and thickness1 resembles that of the ,cetaceous crania2 and what is of still more importance1 they also demonstrate the existence and form of the frontal sinuses4 ,the cavity of the nose is extensive1 and the remains of the ossa spongiosa superiora testify that the ,toxodon enjoyed the sense of smell to a degree equal at least to that of the ,hippopotamus4 ,the sphenoid bone resembles that of the ,hippopotamus1 but it contributes a larger share to the formation of the internal pterygoid processes 7p1 ,pl4 ,,ii472 these are of a simple form1 and more developed than in the ,hippopotamus2 they project outwards to a greater extent1 and terminate in a point4 ,the sphenoid also sends off a short and thick pointed process from the posterior part of the base of the internal pterygoid processes4 ,the ala of the sphenoid does not rise so far into the orbit1 nor does it articulate with the parietal bone1 as in the ,hippopotamus2 but in this part of its structure1 is the same as in the ,rhinoceros4 ,the spheno-palatine foramen is relatively larger than in the above-named ,pachyderms1 and is bounded above by the descending orbital plate of the frontal bone4 ,the palatal processes of the palatine bones terminate anteriorly between the last molars1 and extend backwards for some distance beyond the alveolar processes1 increasing the extent of the bony roof of the mouth posteriorly3 this is a structure in which the ,toxodon deviates both from the ,rodents1 and ,pachyderms1 and resembles the ,armadillos among the ,edentata2 excepting that the postdental part of the bony palate in the ,toxodon is suddenly contracted in breadth4 ,the palato-maxillary suture is in the form of a chevron1 with the angle directed forwards1 as in the ,hippopotamus and ,capybara1 but truncated4 ,the superior maxillary bones 7,f1 ,pl4 ,,ii47 are united posteriorly to the malar1 as above described3 they ascend and join the frontal and nasal bones3 their outer surface is almost vertical1 smooth1 and slightly undulating2 perforated at its posterior part by the ant-orbital foramen1 and joined anteriorly to the intermaxillaries by a suture running in the sigmoid direction 7as shewn in ,pl4 ,,ii47 from the middle of the nasal cavity1 to within four inches of the anterior boundary of the upper jaw4 ,we have1 in the position and extent of this suture1 and the absence of tusks and their large prominent sockets1 a most important difference between the ,toxodon and ,hippopotamus4 ,the chief peculiarity in the maxillary bones1 obtains in the arched form of the alveolar processes1 corresponding to the shape and position of the grinders above described1 and which are peculiar among known mammalia to the present genus4 ,the palatal surface of the maxillary bones is obliquely perforated by two large foramina1 from which two deep longitudinal grooves extend forwards1 and are gradually lost2 we find the posterior palatine foramina represented by similar grooves and foramina in the ,capybara4 ,the intermaxillary bones 7,d1 ,pls4 ,,ii4 and ,,iii471 though large1 are relatively of less extent than in the ,rodents generally4 ,the nasal processes do not reach the frontal bone1 but are limited to the anterior half of the nasal boundary2 approaching in this respect to the ,herbivorous ,cetacea4 ,in the outward expansion of their anterior extremities1 the intermaxillaries resemble those of the ,hippopotamus1 in which1 however1 this character is more strongly marked4 ,the intermaxillaries in the ,hippopotamus are also much less firmly united to the maxillary bones than in the ,toxodon1 and are consequently commonly lost in the fossil crania4 ,on the palatal surface of the intermaxillary bones there are two grooves which diverge forwards from the line of the suture2 and anteriorly to these grooves there are the two large anterior palatine foramina4 ,the maxillo-intermaxillary sutures on the palate converge as they extend backwards to a point2 there appears to have been a fissure left between this suture and the mesial suture of the intermaxillaries2 in which structure the ,toxodon resembles the ,hippopotamus4 ,after summing up the different affinities1 or indications of affinity1 which are deducible from the cranium of this most curious and interesting fossil mammal1 we are led to the conclusion1 assuming it to have had extremities cased in hoofs1 that it is referrible to the ,order ,pachydermata4 ,but the structure1 form1 and kind of teeth in the upper jaw1 prove1 indisputably1 that the gigantic ,toxodon was intimately related to the ,rodent ,order4 ,from the characters of this order1 as afforded by the existing species1 the ,toxodon1 however1 differs in the relative position of the supernumerary incisors1 and in the number1 and direction of the curvature1 of the molars4 ,if1 moreover1 the lower jaw1 next to be described1 belong1 as ,i believe1 to the ,toxodon1 the dental character of the genus will be incisors 2 pro laniariis diastema2 molares 4 ,the ,toxodon again deviates from the true ,rodentia1 and resembles the ,wombat1 and the ,pachyderms1 in the transverse direction of the articular cavity of the lower jaw4 ,it deviates from the ,rodentia1 and resembles the ,pachydermata in the relative position of the glenoid cavities and zygomatic arches1 and in many minor details already alluded to4 ,in the aspect of the plane of the occipital foramen1 and occipital region of the skull2 in the form and position of the occipital condyles2 in the aspect of the plane of the anterior bony aperture of the nostrils2 and in the thickness and texture of the osseous parietes of the skull1 the ,toxodon deviates both from the ,rodentia and existing ,pachydermata1 and manifests an affinity to the ,dinotherium and ,cetaceous ,order1 especially the ,herbivorous section4 ,at present we possess no evidence to determine whether the extremities of the ,toxodon were organized on the ungulate or unguiculate type1 nor can we be positive1 from the characters which the skull affords1 that the genus may not be referrible to the ,mutica of ,linnus2#ad although the development of the nasal cavity and the presence of large frontal sinuses render it extremely improbable that the habits of this species were so strictly aquatic1 as the total absence of hinder extremities would occasion4 ,where the dentition of a mammiferous animal is strictly carnivorous1 this structure is obviously incompatible with a foot incased in a hoof3--but where the teeth are adapted for triturating vegetable substances the case is different4 ,if animals so characterized are of small size and seek their food in trees1 or if they burrow for roots or for shelter1 the vegetable type of dentition must co-exist with unguiculate extremities1 as in the ,edentata and ,rodentia generally3 but the largest genus 7,hydrochrus7 of the ,rodent ,order1 whose affinity to the ,pachydermata is manifested in its heavy shapeless trunk1 thinly scattered bristly hair1 and many other particulars1 has each of its toes inclosed in a miniature hoof4 ,the affinity above alluded to1 is too obvious to have escaped popular notice1 and the ,capybara1 from its aquatic habits1 has obtained the name of ,water-hog4 ,it is highly interesting to find that the continent to which this existing aberrant form of ,rodent is peculiar1 should be found to contain the remains of an extinct genus1 characterized by a dentition which closely resembles the ,rodent type1 but manifesting it on a gigantic scale1 and tending to complete the chain of affinities which links the ,pachydermatous with the ,rodent and ,cetaceous ,orders4 ,,admeasurements ,,of ,,the ,,cranium ,,of ,,toxodon4 feet inches lines ,extreme length #b #d ,extreme breadth #a #d ,extreme height1 7exclusive of the lower jaw7 #aj ,length of zygomatic process #a #a #f ,depth or vertical extent of do4 #f ,transverse extent of zygomatic fossa #f ,transverse diameter of cranium between the zygomatic arches #e ,transverse diameter of occipital plane of the cranium #a ,from the outside of one condyle to that of the opposite condyle #h #f ,length of the bony palate #a #f ,extreme breadth of ditto #f ,breadth of palate at the intermaxillary suture #b #f ,breadth of palate behind the molar alveoli #c ,longitudinal extent of the molar alveoli #i #f ,longitudinal extent of the diastema #e #f ,transverse diameter of posterior nasal aperture #c #i ,transverse diameter of occipital foramen #c ,transverse diameter of glenoid cavity #d #f ,antero-posterior do4 of ditto #a ,,description ,,of ,,fragments ,,of ,a ,,lower ,,jaw ,,and ,,teeth ,,of ,a ,,toxodon4 ,found at ,bahia ,blanca1 in latitude #ci on the ,east coast of ,south ,america4 ,in looking over some fragments of jaws and teeth1 forming part of ,mr4 ,darwin's collection of ,south ,american mammiferous remains1 and which had been set aside with mutilated specimens referrible to species belonging to the family of ,edentata1 my attention was caught by the appearance of roots of teeth projecting1 in a different direction from the grinders1 from the fractured anterior extremity of a lower jaw1 and ,i was induced to examine minutely the structure of the teeth in this specimen1 and to search the collection for corresponding fragments4 ,the result was the discovery of portions of the two rami1 and the commencement of the symphysis of a lower jaw1 containing anteriorly the roots of six incisors1 and at least six molars on each side2 but as the rami had been fractured through the middle of the sixth alveolus1 the number of grinders may have corresponded with those in the upper jaw of the ,toxodon4 ,the most perfect of these fragments is figured in ,pl4 ,v4 figures #a and #d2 figure #b shows the form of the teeth in transverse section1 and the disposition of the enamel upon the grinding surface of the molars on the right side1 as restored from a comparison of the fractured teeth in the two rami4 ,from the remains of the symphysis shown at fig4 #d1 it will be seen that the jaw was remarkably compressed1 or narrow from side to side2 while the rami 7fig4 #a47 were of considerable depth1 in order to give lodgment to the matrices and bases of grinders enjoying uninterrupted growth4 ,the pulps of the six incisors in this lower jaw are arranged in a pretty regular semicircle1 whose convexity is downwards2 the teeth themselves are directed forwards1 and curved upwards1 like the inferior incisors of the ,rodentia4 ,the form and degree of the curvature are shown in the almost perfect incisor 7,pl4 ,v4 fig4 #e7 which corresponds with the left inferior incisor of the lower jaw1 and was found in the same stratum1 but belonged to another individual4 ,these incisors are nearly equal in size3 they are all hollow at their base1 and the indurated mineral substance impacted in their basal cavities well exhibits the form of the vascular pulps which formerly occupied them4 ,sufficient of the tooth itself remains in four of the sockets to show that these incisors1 like the nearly perfect one 7fig4 #e71 had only a partial investment of enamel2 but though in this respect1 as well as in their curvature and perpetual growth1 they resemble the dentes scalprarii of the ,rodentia1 they differ in having a prismatic figure1 like the inferior incisors of the ,sumatran ,rhinoceros1 or the tusks of the ,boar4 ,two of the sides1 viz41 those forming the anterior convex and mesial surfaces of the incisor have a coating of enamel1 about half a line in thickness1 which terminates at the angles between these and the posterior or concave surface4 ,in plate ,v4 fig4 #d1 the enamel of the broken incisors is represented by short lines1 showing the direction of its crystalline fibres2 the white space immediately within the enamel shows the thickness of the ivory at the base of the tooth1 the included gray substance represents a section of the formative matrix or pulp of the tooth1 which was of the usual conical form3 the inferior broken end of the incisor 7fig4 #e17 appears to have been distant about one-third from the apex of the pulp4 ,from the relative position of the bases or roots of these incisors1 we may infer that they diverged from each other as they advanced forwards1 in order to bring their broadest cutting surfaces into line4 ,that they were opposed to teeth of a corresponding structure in the upper jaw is proved by the oblique chisel-like cutting surface of the more perfect incisor3 and it is not without interest to find that the presence of dentes scalprarii at the anterior part of the mouth has not been necessarily limited to ,mammalia of small size4 ,the position of the pulps of these incisors1 in close proximity with the anterior grinders1 corresponds with the position of the pulps of the incisors in the upper jaw of the ,toxodon1 and indicates1 in conjunction with the size of the pulps1 that a considerable extent of the inferior incisors was lodged in the substance of the anterior part of the jaw4 ,it is most likely that no vertically directed tooth would be developed in the part of the jaw so occupied by the curved bases of the incisors1 and hence a diastema or toothless space would intervene between the molars and incisors of this lower jaw1 as in the upper jaw of the ,toxodon4 ,it is interesting1 also1 to observe1 that as the deviations from the ,rodent type1 which occur in the cranium of the ,toxodon1 are the same1 in some instances1 as those which obtain in the ,wombat2 so we find a corresponding deviation in the size and relative position of the inferior incisors1 which1 as in the ,wombat1 terminate anterior to the molar teeth1 instead of extending backwards beyond the last grinder1 as in most of the true ,rodents4 ,the ,capybara presents the nearest approach to this structure1 the pulps of the inferior incisors being situated opposite the interspace of the first and second grinders4 ,the molar teeth1 in this mutilated lower jaw1 like those in the upper jaw of ,toxodon1 had persistent pulps1 as is proved by the conical cavity at their base1 as represented in fig4 #c2 they consequently required a deep socket1 and a corresponding depth of jaw to form the socket and protect the pulps4 ,in order to economise space1 and to increase the power of resistance in the tooth1 and perhaps1 also1 to diminish the effects of direct pressure on the highly vascular and sensible matrix1 we find the molars and their sockets are curved1 but in a less degree than those of the upper jaw of the ,toxodon4 ,they correspond1 however1 with the superior molars of the ,toxodon in the antero-posterior diameter1 in being small and simple at the anterior part of the jaw1 and by increasing in magnitude and complexity as they are situated more posteriorly4 ,they are1 however1 narrower from side to side2 but supposing them to belong to the ,toxodon1 it would agree in this respect with most other large herbivorous mammalia2--the fixed surface for attrition in the upper jaw being from obvious principles more extensive than the opposed moveable surface in the lower jaw4 ,the first grinder1 in the lower jaw here described 7,pl4 ,v4 fig4 #b71 is of small size and simple structure1 being surrounded with a coating of enamel of uniform thickness1 and without any fold penetrating the substance of the tooth4 ,it is more curved than any of the other molars1 and appears to have differed from the external incisor only in its entire coating of enamel and direction of growth2 it is interesting1 indeed1 to find so gradual a transition1 in structure1 from molar to incisive teeth1 as this jaw presents2 for the robust incisors may here be regarded as representing molars simplified by the partial loss of enamel1 and with a change in their direction4 ,in the second molar1 we find an increase in the antero-posterior diameter1 and in the length of the tooth1 and the enamel at the middle of the outer side makes a fold which penetrates a little way into the tooth2 the line of enamel1 on the inner side1 is slightly concave and unbroken4 ,the third molar presents an increase of dimensions in the same directions as the second2 the enamel on the outer side of the tooth presents a similar fold1 but it is directed a little more backwards4 ,in the fourth molar1 besides a further increase of size1 and a corresponding but deeper fold of enamel in the external side of the tooth1 we have the grinding surface rendered more complicated by two folds of enamel entering the substance of the tooth from the inner side3 these folds divide the antero-posterior extent of the tooth into three nearly equal parts2 they are both directed obliquely forwards1 half-way across the substance of the ivory4 ,the fifth molar presents the same structure as the fourth1 which it exceeds only slightly in size4 ,in the sixth molar we have a proportionally greater increase of size in the antero-posterior diameter1 which measures two inches2 but the lateral diameter is but slightly augmented2 its structure resembles that of the fifth4 ,as these grinding teeth by no means increase in the lateral diameter in the same proportion as in their antero-posterior diameter1 the posterior ones present1 but in a greater degree1 the compressed form which characterizes the grinders of the upper jaw of the ,toxodon4 ,it will be seen1 however1 that there is a difference in the structure of the grinders in this fragment of the lower jaw and those of the upper jaw of the ,toxodon4 ,in the lower grinders there are two folds of enamel proceeding from the inner side of the tooth into its substance1 whilst in the upper grinders there is only one fold continued from the inner side2 in the lower grinders there is also a fold of enamel reflected into the substance of the tooth from the outer surface1 while in the upper grinders of ,toxodon we find the enamel coating on the outer side of the tooth merely bent inwards1 so as to describe1 in the transverse section1 a gently undulating line2 fig4 #g1 ,pl4 ,v4 is the grinding surface of the sixth molar1 right side1 upper jaw4 ,but this difference of structure is by no means incompatible with the co-existence of the two series of teeth in the same animal1 since we find the grinders of the upper and lower jaws presenting differences of structure of equal degree in existing herbivorous species4 ,if we examine the jaws of the ,horse1 for example1 we shall find not only an equal amount of difference in the structure of the upper and lower grinders1 but that they deviate from one another in a very similar manner to that above described in the ,toxodon4 ,in this comparison attention should be confined to the course of the external enveloping layer of enamel1 leaving out of consideration the central crescentic islands of enamel which constitute the additional complexity of the ,horse's grinder4 ,viewing then the course of the external coat of enamel on the worn surface of the tooth1 we find it describing on the outer side of the tooth in the upper jaw an undulating line1--a middle convexity being situated between two concavities2 on the inner side of the tooth one fold of enamel penetrates to the middle of the tooth1 and on each side of this there is a smaller fold4 ,but in the lower jaw the line of enamel on the outer side of the tooth1 instead of merely bending outwards midway in its course1 is reflected a little way inwards2 while on the opposite1 or inner side of the tooth1 the enamel sends two extensive folds into the substance of the tooth1 opposite to the interspace of which the shorter fold projects from the outer side4 ,now1 on the supposition that the fragment of the lower jaw here described belongs to the ,toxodon1 the kind and degree of difference in the complexity of the grinding surface of the teeth in the upper and lower jaw1 are remarkably analogous to those which exist in the ,horse4 ,i have only further to remark that in the ,horse the inflected folds of enamel1 instead of being simple and straight with the two constitutive layers in apposition1 as in the ,toxodon1 are irregular in their course1 with cmentum intervening between the constitutive layers1 which also diverge from each other at their angle of reflection1 so as to augment the amount of dense material which enters into the composition of the tooth4 ,many analogous examples will readily occur to the experienced comparative anatomist4 ,the ,horse has been adduced as one to which reference can very readily be made2 but ,i would also cite the ,sumatran ,rhinoceros1 the skull of which1 in the ,hunterian collection1 has already been alluded to4 ,in this species the anterior grinders1 in both jaws1 are small and simple1 and increase in complexity as they recede backwards4 ,the third superior grinder 7fig4 #h1 ,pl4 ,v47 presents a single fold of enamel1 reflected obliquely forwards from the inner side half-way across the tooth2 the outer line of enamel describes a simply undulating line4 ,the opposite grinder of the lower jaw 7fig4 #i1 ,pl4 ,v47 has only one-half the breadth of the upper one1 but has its grinding surface further complicated by having two inflected folds of enamel from the inner side1 and one shorter and broader fold from the outer side4 ,this tooth1 therefore1 presents a close resemblance to one of the posterior grinders of the lower jaw of the ,toxodon1 but differs essentially in being of limited growth1 and consequently in having fangs4#ae ,in speculating upon the nature of the organized substances which the teeth of the ,toxodon were destined to grind down1 we must not only take the structure of the tooth into consideration1 but also the power of perpetual renovation1 which will compensate for the defective quantity of enamel in the grinders of the ,toxodon1 as compared with those of the existing ,ruminants and ,pachyderms1 whose grinders1 when once completed1 receive no further addition of dental substance at their base4 ,the ,toxodon1 in this character of its dentition1 participated in the same advantages with the ,capybara and the ,megatherium4 ,although we have been enabled to observe the structure of the grinding teeth of the upper jaw of the ,toxodon in two examples only2 one1 an insulated perfect grinder corresponding to the sixth alveolus on the right side1 and the other1 a portion of the last grinder of the left side remaining in the socket of the head previously described1 yet from the relations subsisting between socket and tooth1 a very satisfactory opinion may be formed of the structure of those teeth which are wanting1 as well as of their size4 ,it thus appears1 that the grinders of the upper jaw of the ,toxodon1 are small and simple at the anterior part of the jaw1 and that they increase 7chiefly in antero-posterior extent7 in size1 as well as in complexity1 as they recede backwards in the jaw4 ,in this respect1 as well as in size1 the teeth1 in the fragments of the lower jaw just described1 exactly correspond4 ,there is1 however1 a slight difference in the lateral diameter of the two sets of grinders1 those of the lower jaw being narrower1 as is usually the case1 but not in the same degree as in the ,horse or ,ruminant4 ,a greater difference obtains in the degree of curvature of the two sets of molars1 those of the lower jaw1 especially the posterior grinders1 being much less bent than the corresponding teeth of the upper jaw4 ,it is necessary to observe1 also1 that the convexity of the curve of the inferior grinders is directed outwards1 as in the superior grinders2 while in the ,guinea ,pig and ,wombat1 which have also curved grinders1 the convexity is outwards in the lower jaw1 and inwards in the upper jaw4 ,nevertheless1 if we take into consideration the close similarity which exists between the teeth of the upper jaw of the ,toxodon1 and those of this lower jaw in more essential points1 as in their persistent pulps1 their characteristic structure and form1 the depth of their sockets1 and their relative sizes and complexity2 and when we consider how the depth of this lower jaw1 and its narrowness in the transverse direction1 corresponds with the characteristic form of the upper jaw of the ,toxodon1 and that to these resemblances is added an apparatus of incisors adequate to oppose the great dentes scalprarii of the upper jaw1 the conclusion seems irresistible1 that the lower jaw1 here described1 must be referred1 if not to the same1 at least to a nearly allied species of ,toxodon1 as that to which the large cranium belonged4 ,further researches in ,south ,america1 it is hoped1 will lead1 ere long1 to the completion of our knowledge of the osteology of this very remarkable and interesting genus of extinct mammiferous animals4 ,,description ,,of ,,parts ,,of ,,the ,,skeleton ,,of ,,macrauchenia ,,patachonica2 ,a large extinct ,mammiferous ,animal1 referrible to the ,order ,pachydermata2 but with affinities to the ,ruminantia1 and especially to the ,camelid4 ,in the preceding pages the nature and affinities of a large extinct ,mammal were attempted to be determined from the cranium and teeth exclusively3 we come now to consider the remains of a quadruped consisting of bones of the trunk and extremities1 without a fragment of a tooth or of the cranium to serve as a guide to its position in the zoological scale4 ,it may appear1 even to anatomists and naturalists familiar with the kind of evidence afforded by a fossil fragment1 that an opinion as to the relation of the present species to a particular family of ,ruminants1 formed without a knowledge of the important organs of manducation1 must be vague and doubtful1 but the evidence about to be adduced1 will be regarded1 it is hoped1 as more conclusive than could have been priori expected4 ,the portions of the skeleton of the animal--which1 in relation to the affinity above alluded to1 as well as from the length of its neck1 ,i propose to call ,macrauchenia#af--were discovered by ,mr4 ,darwin in an irregular bed of sandy soil1 overlying a horizontal accumulation of gravel on the south side of ,port ,st4 ,julian3 and independently of the circumstances under which they were found1 their correspondence with each other in size1 colour1 texture and general character prove them to have belonged to one and the same individual4 ,these remains include two cervical vertebr1 seven lumbar vertebr1 all more or less fractured2 a portion of the sacrum and ossa innominata2 fragments of the right scapula2 of the right radius and ulna1 and right fore-foot2 the right femur nearly entire1 the proximal and distal extremities of the right tibia and fibula2 and a metatarsal bone of the right hind-foot4 ,before entering upon the description of these remains1 a few observations may be advantageously premised on some of the distinguishing characters of the ,camelid4 ,it is well known that the ,camels and ,llamas deviate in their dentition1 viz41 in the presence of two incisors in the upper jaw1 from the true ,ruminants2 and we cannot avoid perceiving that in this particular the direction in which they deviate tends towards the conterminous ,ungulate ,order1 in which incisor teeth are rarely absent in the upper jaw4 ,they also further deviate from the ,ruminants and approach the ,pachyderms in the absence of cotyledons in the uterus and fetal membranes2 having1 instead thereof1 a diffused vascular villosity of the chorion1 as in the sow and mare4 ,but besides these characters1 by which1 in receding from one type of hoofed mammalia1 the ,camelid claim affinity with another1 there are many parts of their organization peculiar to themselves2 of some of these peculiarities1 the relation to the circumstances under which the animal exists1 can be satisfactorily traced2 in others1 the connection of the structure with the exigencies of the species1 is by no means obvious1 and in this predicament stands the osteological peculiarity1 which is immediately connected with our present subject--a peculiarity in which the ,camelid differ not only from the other ,ruminants1 but from all other existing ,mammalia1 and which consists in the absence of perforations for the vertebral arteries in the transverse processes of the cervical vertebr1 the atlas excepted4 ,i may observe that what is described as a perforation of a single transverse process in a cervical vertebra is essentially a space intervening between two transverse processes1 a rudimental rib1 and the body of the vertebra4 ,in the cold-blooded ,saurians1--in which the confluence of the separate elements of a vertebra takes place tardily and imperfectly1 if at all1--the nature of the so called perforation of the transverse process is very clearly manifested1 as in the cervical vertebr of the ,crocodile1 in which the interspace of the inferior and superior transverse processes is closed externally by a separate short moveable cervical rib4 ,in the ,ornithorhynchus paradoxus the vertebra dentata also preserves throughout life this condition of its lateral appendages3 in other ,mammalia it is only in the ftal state that the two transverse processes are manifested on each side with their extremities united by a distinct cartilage1 which afterwards becomes ossified and anchylosed to them4 ,in the ,hippopotamus the inferior transverse process sends downwards a broad flat plate extended nearly in the axis of the neck1 but so obliquely1 that the posterior margins of these processes1 in one vertebra1 overlap the anterior ones of the succeeding vertebra below1 like the cervical ribs in the ,crocodile2 the same structure obtains in many other mammalia1 especially in the ,marsupials4 ,in the ,giraffe1 the inferior transverse processes are represented by relatively smaller compressed lamin1 projecting obliquely downwards and outwards from the anterior and inferior extremity of the body of the vertebra4 ,the superior transverse processes in this animal are very slightly developed in any of the cervical vertebr1 and the perforation for the vertebral artery is above and generally in front of the rudiment of this process1 being continued as it were through the side of the substance of the body of the vertebr4 ,in the long cervical vertebr of the ,camel and ,llama1 the upper and lower transverse processes are not developed in the same perpendicular plane on the sides of the vertebr1 but at some distance from each other2 the lower transverse processes 7a1 fig4 #a1 ,pl4 ,,vi42 a1 fig4 #a1 #c1 #d1 ,pl4 ,,vii47 being given off from the lower part of the anterior extremity of the body of the vertebra2 the upper ones 7b1 fig4 #a1 ,pl4 ,,vi42 a1 fig4 #a1 #c1 #d1 ,pl4 ,,vii47 from the base of the superior arch near the posterior part of the vertebra1 or from the sides of the posterior part of the body of the vertebr4 ,the extremities of these transverse processes do not become united together1 but they either pass into each other at their base1 or continue throughout life separated by an oblique groove 7as in fig4 #a1 ,pl4 ,,vi47 ,this groove would not1 however1 afford sufficient defence for the important arteries supplying those parts of the brain which are most essential to life2 and1 accordingly the vertebral arteries here deviate from their usual course1 in order that adequate protection may be afforded to them in their course along the neck4 ,from the sixth to the second cervical vertebr inclusive in the ,aucheni1 and from the fifth to the second inclusive in the ,cameli1#ag the vertebral arteries enter the vertebral canal itself1 along with the spinal chord1 at the posterior aperture in each vertebra1 run forwards on the outside of the dura mater of the chord between it and the vertebral arch1 and when they have thus traversed about two-thirds of the spinal canal1 they perforate respectively the superior vertebral lamin1 and emerge directly beneath the anterior oblique or articulating processes1 whence they are continued along with the spinal chord into the vertebral canal of the succeeding vertebra1 and perforate the sides of the anterior part of the superior arch in like manner2 and so on through all the cervical vertebr until they reach the atlas1 in which their disposition1 and consequently the structure of the arterial canals1 resemble those in other ,ruminants4 ,the two cervical vertebr of the ,macrauchenia present precisely the structure and disposition of the bony canals for the vertebral arteries which are peculiarly characteristic of the ,camelid among existing ,mammalia4 ,in ,plate ,,vi4 fig4 #b1 the groove and orifices of the canal for the vertebral artery are shown in a section exposing the spinal canal3 in ,plate ,,vii4 figures #a and #c exhibit the orifices at the commencement of the arterial canals1 as seen in a posterior view of the vertebr2 in figs4 #b and #d1 the terminations of the same canals are shown1 in the anterior view of the same vertebr2 the smaller figures 7#c and #d7 are taken from the fourth cervical vertebra of a ,llama4 ,the vertebr of the ,macrauchenia also closely resemble the middle cervical vertebr of the ,vicugna and ,llama in their elongated form2 approaching the ,auchenial division of the ,camelid1 and deviating from the true ,camels in the relations of the length of the body of the vertebra to its breadth and depth1 and in the much smaller size of the inferior processes4 ,excepting the ,giraffe1 there is no existing mammal which possesses cervical vertebr so long as the ,macrauchenia2 but the cervical vertebr of the ,giraffe1 differ in the situation of the perforations for the vertebral arteries1 and in the form of the terminal articular surfaces1 as will be presently noticed4 ,both of the cervical vertebr of the ,macrauchenia here described1 are of the same size1 each measures six inches and a half in extreme length1 two inches1 ten lines in breadth1 and two inches1 four lines in depth4 ,in the ,giraffe and the ,camelid1 the spinous processes are thin lamin of considerable extent in the axis of the vertebra1 but rising to a very short distance above the level of the vertebral arch3 the spinous processes have the same form in the corresponding vertebr of the ,macrauchenia1 but present a still greater longitudinal extent2 they commence at the interspace of the anterior oblique processes1 and extend to opposite the base of the posterior oblique processes2 the upper margin describing a gentle curve1 as shown in fig4 #a1 ,pl4 ,,vi4 ,the transverse processes also present the form of slightly produced1 but longitudinally extended1 lamin3 their disposition is essentially the same as in the ,camelid1 but more nearly corresponds with the modifications presented by the ,aucheni4 ,the inferior transverse processes1--those which are alone developed in fish1 but which are not present in any other vertebr save the cervical1 in mammalia1--these processes in the ,macrauchenia are continued from the sides of the under surface of the anterior part of the body of the vertebra2 their extremities being broken off1 it cannot be determined how far they extended from the body of the vertebr1 but they gradually subside as they pass backwards3 the superior transverse processes are continued outwards from the sides of the posterior part of the body of the vertebra1 and gradually subside as they advance forwards along three-fourths of the body of the vertebra3 they are not continued into the anterior and inferior transverse processes1 as in the ,vicugna1 but are separated therefrom by a narrow and shallow groove4 ,the articular1 or oblique processes1 closely resemble those of the ,auchenia in form1 and in the direction of the articular surfaces2 those of the anterior processes looking inwards and a little upwards2 those of the posterior1 outwards and a little downwards4 ,in the ,macrauchenia a small longitudinal process 7c1 fig4 #b1 ,pl4 ,,vii47 is given off immediately below the base of the anterior oblique process2 this structure is not observable in any of the cervical vertebr of the ,giraffe or ,camelid4 ,in the form of the articulating surfaces of the bodies of the vertebr the ,macrauchenia deviates from the ,giraffe and ,camel1 but resembles the ,aucheni4 ,in the ,giraffe and ,camel the anterior articulating surface is convex and almost hemispheric1 the posterior surface is proportionally concave1 so that the cervical vertebr are articulated by ball and socket joints2 yet not1 as in most ,reptiles1 with intervening synovial cavities1 but by the concentric ligamentous intervertebral substance characteristic of the ,mammiferous class4 ,in the ,llama and ,vicugna1 the degree of convexity and concavity in the articular surface of the bodies of the cervical vertebr is much less than in the ,camels2 and in consequence they carry their necks more stiffly and more in a straight line4 ,in ,macrauchenia the anterior articulating surface 7fig4 #b1 ,pl4 ,,vii47 presents a still slighter convexity than in the ,llama 7fig4 #d1 ,pl4 ,,vii471 and the posterior surface 7fig4 #a1 ,pl4 ,,vii47 presents a correspondingly shallower concavity4 ,the form of the extremities of the body of the vertebr1 especially of the posterior1 is sub-hexagonal1 the breadth being to the depth as eight to five4 ,the sides and under part of the vertebr are slightly concave2 on the inferior surface there are two ridges1 continued forwards from the posterior margin of the vertebra1 each situated about an inch distant from the middle line2 they converge as they pass forwards1 and are gradually lost in the level of the vertebra2 their greatest elevation does not exceed half an inch4 ,in the ,aucheni there is a longitudinal protuberance in the mesial line1 instead of the two ridges4 ,the two long cervical vertebr of the ,macrauchenia are also characterized by the maintenance of an almost uniform diameter of the body1 both in its vertical and transverse extent2 the cervical vertebr of the ,vicugna come nearest to them in this respect2 those of the ,camel deviate further in the large excavation at the under part of the body4 ,the long vertebral or spinal canal offers a slight enlargement at the two extremities2 this structure which is generally in the ratio of the extent of motion of the vertebr on each other is more marked in the ,camel1 where the form and mode of articulation of the bodies of the vertebr are designed to admit of a free and extensive inflection of the cervical vertebr2 and the result of this structure is very obvious in the sigmoid flexure of the neck in the living animal4 ,in the ,aucheni1 on the contrary1 the neck is carried less gracefully erect and in an almost straight line1 and the form of the vertebr and the nature of their joints correspond1 as we have seen1 to this condition4 ,from the length of the bodies of the cervical vertebr of the ,macrauchenia1 and the almost flattened form of their anterior and posterior articular surfaces1 ,i infer that the long neck in this singular quadruped must have been carried in the same stiff and upright position as in the ,vicugna and ,guanaco4 ,the following individual differences are observable in the two cervical vertebr of the ,macrauchenia2--in the posterior one the superior arch is wider and with thicker parietes1 the body is more concave below1 and the inferior transverse processes have a more lengthened origin4 ,not a fragment of dorsal vertebr1 ribs or sternum1 is included in the collection of the bones of the ,macrauchenia2 but fortunately seven lumbar vertebr1 forming a consecutive series of the same individual as that to which the cervical vertebr belonged1 were obtained1 all more or less fractured1 but all sufficiently perfect to demonstrate their true nature4 ,these vertebr1 although not possessing such distinctive characters as the cervical1 contribute by no means an unimportant element towards the illustration of the osteology of the ,macrauchenia1 and support the view which ,i have taken of its affinities2 for1 although1 as will be seen from the structure of its extremities1 this animal must be referred to the ,order ,pachydermata1 yet no existing species of that order has more than six lumbar vertebr2 whilst among the ,ruminants it is only in the ,camel1 ,dromedary1 ,llama and ,vicugna1 that the lumbar vertebr reach the number seven1--the same number which characterizes the extinct annectant species in question4 ,the dimensions of the vertebr in the ,macrauchenia present the same relations to the two cervical vertebr above described1 which the lumbar vertebr of the ,vicugna bear to the third1 fourth1 or fifth of its cervical vertebr4 ,but here we begin to discover modifications of form1 in which the ,macrauchenia deviates from the ,camelid1 and approaches the ,pachyderms1 as the ,horse and ,hippopotamus2 and these indications become stronger as the vertebr approach the sacrum4 ,in the ,camel1 as well as in the ,horse and ,hippopotamus1 the bodies of the lumbar vertebr diminish in vertical extent1 or become flatter1 as they approach the sacrum2 but this character is more strongly marked in the ,macrauchenia than in either of the above species4 ,but in the ,camelid the transverse processes of the lumbar vertebr1 are elongated1 flattened1 and narrow1 resembling ribs1 except that they are nearly straight2 and this is more particularly the case with the transverse processes of the last lumbar vertebr1 which are the narrowest of all in proportion to their length1 and stand freely out without touching the sacrum4 ,the transverse processes of the lumbar vertebr of the ,giraffe resemble those of the ,camel1 but are relatively smaller and shorter4 ,in the ,hippopotamus the transverse processes of the lumbar vertebr are much broader in proportion to their length than in any of the ,ruminants1 and they increase in breadth to the last lumbar vertebra1 which presents in addition1 the following characters2 each transverse process sends off from its posterior margin a thickened and transversely elongated protuberance1 which supports a flattened articular surface adapted to a corresponding surface on the anterior part of the transverse process of the first sacral vertebra3 it likewise presents on its anterior edge a flattened and rough surface1 which is closely attached by ligamentous substance to the opposite part of the transverse process of the penultimate lumbar vertebra4 ,a similar structure exists in the last two lumbar vertebr of the ,rhinoceros1 ,tapir1 and ,horse4 ,in the latter animal1 anchylosis of these articulating surfaces of the lumbar and sacral vertebr generally takes place with age1 and1 judging from the character of the same surfaces in the ,hippopotamus1 the motion of its lumbar vertebr upon the sacrum may in like manner become ultimately arrested4 ,now in the ,macrauchenia1 as in the ,pachyderms above cited1 the transverse processes of the last lumbar vertebr are of considerable thickness and extent1 and are joined by enarthrosis to the transverse processes of the sacrum2 but the bony structure of these joints would indicate that they were not subject to be obliterated by anchylosis4 ,the articular surfaces which project from the posterior part of the transverse processes of the last lumbar vertebr present a regular and smooth concavity1 adapted to a corresponding convexity in the transverse processes of the first sacral vertebra4 ,these articulating surfaces have evidently been covered with smooth cartilage2 they present a pretty regular transverse ellipsoid form4 ,a view of the three joints by which1 independently of the two oblique processes1 the last lumbar vertebra of the ,macrauchenia was articulated with the sacrum1 is given in ,plate ,,viii4 fig4 #a4 ,the transverse processes of the posterior lumbar vertebra1 besides their agreement with those of the ,horse and ,hippopotamus in the structure just described1 also correspond with them in general form1 and deviate remarkably from those of the ,camelid in their great breadth4 ,it will be seen that the articulations on the body and transverse processes of the last lumbar vertebra of the ,macrauchenia differ from the corresponding articular surfaces of the ,horse1 inasmuch as the middle surface is convex1 while the two lateral ones are concave1 and these are moreover relatively larger than either in the ,horse or ,hippopotamus3 by this structure the trunk was more firmly locked to that segment of the vertebral column1 which receives and transmits to the rest of the body the motive impetus derived from the hinder extremities1 which are in all quadrupeds the chief powers in progression2 while at the same time the shock must have been diminished by the great extent of interposed elastic cartilages2 and a certain yielding or sliding motion would be allowed between the lumbar vertebr and sacrum4 ,the anterior oblique processes of the lumbar vertebr of the ,macrauchenia 7fig4 #d1 ,pl4 ,,viii47 have concave articular facets turned towards1 and nearly continued into1 each other at their lower extremities2 so as to form together a deep semilunar notch1 into which the corresponding convex articular surfaces of the posterior oblique processes of the adjoining vertebra 7fig4 #c1 ,pl4 ,,viii47 are firmly locked4 ,in the close approximation of the two anterior concave articular facets1 which are separated from each other only by a vertical ridge1 and a rough surface of about three or four lines in breadth1 the lumbar vertebr of the ,macrauchene resemble those of the ,horse1 and differ from those of the ,camel tribe and ,ruminants generally1 in which those surfaces are wider apart4 ,in the hook-like form1 however1 of these articular processes the lumbar vertebr of the ,macrauchene differ from those of the ,horse2 and resemble those of many ,ruminant species1 and of the ,anoplothere2#ah but the degree of concavity of the articulating surface is not so great in the ,macrauchene4 ,it would be interesting to determine the relations which the lumbar vertebr of the ,macrauchene bear to those of the ,palothere2 but the indication which ,cuvier gives of the single lumbar vertebra1 of which he had cognizance in the latter genus#ai is too slight to enable me to enter upon the comparison4 ,the whole length of the lumbar region in the ,macrauchene is twenty inches4 ,when the bodies of these vertebr are naturally adapted together1 they form a slight curve1 indicating that the loins of the ,macrauchene were arched1 or bent downwards towards the sacrum4 ,that the lumbar vertebr were rigidly connected together1 or but slightly flexible1 is evident from the flatness of the articular surfaces of the vertebral body1 and by the circumstance of ossification having extended along the anterior vertebral ligaments1 and produced an anchylosis between the fourth and fifth lumbar vertebr2 7fig4 #b1 c1 ,pl4 ,,viii47 ,this kind of ossification is frequent in aged horses1 and ,i have seen an example of a similar anchylosis of the lumbar vertebr1 by abnormal deposition of bone in their anterior ligaments1 in the skeleton of a ,hippopotamus preserved in the ,senkenbergian ,museum1 at ,frankfort4 ,in preparing the preceding account of the cervical and lumbar regions of the vertebral column of the ,macrauchene1 ,i have felt frequently a strong desire to enter into a comparison between them and the corresponding vertebr of the extinct ,pachyderms of the ,paris ,basin4 ,some of these1 as the ,anoplotherium gracile1 in the length and slenderness of the cervical vertebr1 resemble both ,auchenia and ,macrauchenia2 others1 as the ,palotherium minus1 and probably the rest of the genus1 resemble the ,camelid and ,macrauchenia in having seven lumbar vertebr4 ,cuvier points out the resemblance which the atlas of the ,anoplothere bears to that of the ,camel1 and especially of the ,llama2#bj but he expressly notices the existence of the canals for the vertebral artery in the fifth or sixth cervical vertebra of the ,anoplotherium commune4#ba ,do the cervical vertebr--say from the third to the sixth inclusive--of the ,palotherium present an imperforate condition of their transverse processes1 or exterior part of their sides8 ,cuvier1 who seems not to have been aware of this peculiarity in the ,camelid1 merely notices the absence of these arterial foramina in the last cervical vertebra of the ,palotherium minus1#bb which1 unfortunately for the comparison ,i am desirous of establishing1 is that which most commonly presents this imperforate condition in the ,mammalia generally4 ,as1 however1 the cervical vertebr of the ,palothere had the anterior articular surface of the body convex1 and the transverse processes produced into descending lamin1 it is most probable that they corresponded with the cervical vertebr of the typical ,pachyderms in the condition of their arterial foramina4 ,the sacrum and ossa innominata in the present specimen of ,macrauchenia are very imperfect2 but sufficient is preserved to show that the sacrum was anchylosed to the ilia3 the lower boundary of this anchylosis is marked below by an external ridge1 and by vascular canals and grooves in the substance of the bone1 as in the ,hippopotamus4 ,the body of the sacrum is lost1 but the smooth articular convexities upon the transverse processes adapted to the articular depressions of the last lumbar vertebra are fortunately preserved4 ,the remains of the anterior extremity of our ,macrauchenia include fragments of a left scapula2 the proximal extremities of the anchylosed bones of the right antibrachium2 the metacarpal and most of the phalangeal bones of the right fore-foot4 ,the first-mentioned fragments1 include the head and neck of the scapula1 a small part of its body with the beginning of the spine1 the coracoid process1 and the nearly entire glenoid cavity4 ,this articular surface 7fig4 #b1 ,pl4 ,,ix47 resembles in its general form1 and degree of concavity1 that of the ,camel and ,rhinoceros1 and is deeper than in the ,hippopotamus4 ,the coracoid process is represented by a slightly produced rough1 thick1 and obtuse tuberosity1 situated closer to the glenoid cavity than in the ,camelid or ,rhinoceros1 and having almost the same relative position and size1 as in the ,palotherium crassum4 ,the superior border or costa of the scapula presents much variety in the ,ungulate quadrupeds with which we have to compare the ,macrauchenia4 ,in the ,ruminants its contour forms behind the coracoid a concave sweep1 which advances close to the spine of the scapula4 ,in the ,camel and ,horse the marginal concavity is shallower1 and the distance of the superior costa from the spine of the scapula is greater2 the extent of the supra-spinal fossa increases in the true ,pachyderms1 and the ,macrauchene agrees with them in this structure4 ,in the ,tapir1 however1 the contour of the superior costa is broken by a deep round notch immediately behind the coracoid3 in the ,hippopotamus this process arches in a slight degree backward over a corresponding but wider and shallower notch4 ,in the ,palotherium crassum the concavity of the superior costa1 behind the coracoid1 is as slight as in the ,rhinoceros2 but in the ,macrauchenia the superior costa of the scapula begins to rise or stretch away from the parallel of the spine1 immediately behind the coracoid process4 ,the modifications of the spine of the scapula which characterize respectively the ,ruminants and ,pachyderms have been clearly and concisely set forth by ,cuvier1 who at the same time points out the exceptional condition which the ,camelid present in the production of the acromial angle4 ,it was with peculiar interest and care1 therefore1 that ,i reunited all the fragments of the scapula of the ,macrauchene1 in the hope of gaining from this part of the skeleton as decisive evidence of an affinity to the ,camel as the cervical vertebr had afforded4 ,it unfortunately happens1 however1 that the part of the scapula most important in this comparison is broken off2 yet from this very circumstance1 combined with a slight inclination forwards of the anterior margin of the spine immediately beneath the fractured acromion1 and from the thickness of the fractured surface1 we may infer that the acromial angle of the spine was more produced than in the ordinary ,ruminants1 although evidently in a less degree than in the ,camel tribe4 ,the ,macrauchenia1 however1 surpasses these aberrant ,ruminants1 and equals the ,pachyderms in the elevation and extent of its scapular spine3 but this process commences about half an inch behind the glenoid cavity1 and rises at once to the height of three inches above the plane of the scapula2 in which structure we may trace the same tendency to the ,ruminant type1 as is manifested in the scapula of the ,hippopotamus and ,anoplotherium2 for in most other ,pachyderms the spine increases gradually from its extremities to the middle part4 ,the anterior margin of the spine beneath the short acromion is perforated by an elliptical fissure measuring ten lines1 by three lines4 ,the extent of the spine which is preserved1 measures eight inches and a half2 it is a thin and nearly straight plate of bone1 expanding into a thick and rugged upper margin1 which slightly over-arches the inferior fossa4 7fig4 #a1 ,pl4 ,,ix47 ,in its general form and proportions the spine of the scapula in ,macrauchenia presents the nearest resemblance to that of the ,hippopotamus2 but its origin is closer to the articular surface of the scapula than in this1 or any other ,pachydermal or ,ruminant genus4 ,the portion of the antibrachium of the ,macrauchenia which is preserved1 presents a condition of the radius and ulna intermediate to those which respectively characterize the same bones in the ,pachyderms and ,camels4 ,in the former the radius and ulna are separate bones1 united in the prone position by ligament1 yet so that the movement of supination cannot be performed2 in the ordinary ,ruminants they are partially joined by bony confluence1 which rarely extends to the proximal extremities2 in the ,camel and ,llama the anchylosis of the radius and ulna is so complete1 that no trace of their original separation can be perceived1 and the olecranon appears but as a mere process of the radius4 ,in the ,macrauchenia the anchylosis of the radius and ulna is also complete1 but the boundary line of the two originally distinct bones is very manifest1 and the proportion which each contributes to the great articulating surface for the distal end of the humerus is readily distinguishable4 ,about a sixth part of this surface is due to the head of the radius1 which enters into the composition of the anterior and outer part of the articulation1 and its extent is defined by a depressed line describing a pretty regular curve1 with the concavity directed forwards and a little outwards4 7a1 fig4 #a1 ,pl4 ,x47 ,just below the articular surface a strong triangular rugged protuberance projects from the front of the head of the radius1 for the attachment of the tendon of the biceps4 ,the line of separation of the radius and ulna is indicated on the inner side of the head of the radius by a deep and narrow fissure extending downwards from below the anterior part of the articulating surface2 and on the outer side by a broad groove leading upwards to a deep pit near the proximal end of the antibrachium4 ,we may see by the direction of the head of the radius which is thus defined1 that it crosses obliquely in front of the ulna1 as in the ,elephant1 ,hippopotamus1 and other ,pachyderms1 and that the bones are anchylosed in the prone condition3 below this fissure and groove1 which mark the interosseous line1 the radius and ulna become blended together into one compact bone1 which is flattened from before backwards1 with a well marked ridge on the outer side2 and excavated by a single medullary cavity1 the compact walls of which present a general thickness of one-third of an inch4 ,the proximal articular surface or sigmoid cavity of the antibrachium1 constituted as above described1 resembles that of the ,palothere1 ,tapir1 and the generality of the ,pachyderms in having two depressions1 instead of three1 as in the ,anoplothere1 and ,ruminants4 ,the ,hippopotamus has a slight tendency to the latter structure1 which is also less marked in the ,camel than in the ordinary ,ruminants4 ,in its general form the sigmoid cavity of the ,macrauchene resembles that of the ,hippopotamus more than that of the ,camel4 ,in the ,camel this articular surface is traversed transversely by a broad1 shallow1 and slightly roughened tract1 which divides the smooth surface of the joint into two parts1 one forming the anterior horizontal surface due to the conjoined radius and ulna1 the other forming the vertical concave surface on the anterior part of the base of the olecranon4 ,in the ,hippopotamus there is1 as it were1 an attempt at a similar division of the articulating surface at the proximal end of the antibrachial bones2 a deeper and rougher depression encroaches upon the articulation from its outer side1 but stops when it has reached half-way across4 ,in the ,macrauchenia the roughened surface1 7b4 fig4 #a1 ,pl4 ,x47 commencing also at the outside1 extends only one-third of the way across the articular surface3 it is1 however1 as shallow as in the ,camel4 ,the articular surface on the anterior part of the base of the olecranon is broader in the ,hippopotamus than in the ,camel2 but in the ,macrauchene it is twice as broad as in the ,hippopotamus4 ,the size of the olecranon in the ,macrauchene exceeds that of the ,hippopotamus1 and fortiori that of the ,camel3 indeed in its general magnitude the ,macrauchenia must have fully equalled the largest ,hippopotamus2 but it no doubt had a more shapely1 and less broad and bulky trunk4 ,the olecranon of the ,macrauchenia differs in shape1 both from that of the ,camel and ,hippopotamus2 it terminates above in a three-sided cone with an obtuse apex2 and presents a well-marked protuberance at the outer side of the base1 which is not present in either the ,camel or ,hippopotamus4 ,there is also a strong rugged ridge on the back part of the olecranon which makes an angle before sinking into the level of the ulna below4 ,the confirmation of the close affinity of the ,macrauchenia to the ,pachydermatous ,order1 which the structure of the cervical vertebr alone might have rendered very doubtful1 is afforded by the bones of the right fore-foot 7,pl4 ,,xi472 these are fortunately in so perfect a condition1 as to make it certain that this interesting quadruped had three toes on the fore-feet1 and not more2 and that the fully developed metacarpal bones are distinct1 and correspond in number with the toes1 and are not anchylosed into a single cannon bone1 as in the ,ruminants4 ,the bones preserved are the metacarpals1 proximal phalanges1 and middle phalanges of each of the three toes1 and the distal phalanx of the innermost toe4 ,the proximal end of the innermost metacarpal bone presents three articular surfaces2 the middle facet is the largest1 and the two lateral ones slope away from it at an angle of #de4 ,the middle facet is broad and slightly convex in front1 narrow and concave behind2 the distal articular surface of the trapezoides must have corresponded with this surface2 the outer facet is narrow1 flat1 extends from the fore to the back part of the head of the bone1 and must have been adapted to a corresponding surface on the os magnum2 the inner facet is the smallest1 presents a triangular form1 and is situated towards the back part of the head of the metacarpal bone2 it indicates the existence of a rudimental metacarpal bone1 or vestige of a pollex4 ,below the outermost of the lateral surfaces there is a crescentic articular surface with its concavity directed outwards and downwards 7fig4 #b1 ,pl4 ,,xv471 against which a corresponding convex articular surface of the middle metacarpal abuts1 7fig4 #c1 ,pl4 ,,xv47 ,external to this surface the proximal end of the middle metacarpal bone presents two articular surfaces for the carpus2 the larger one1 which was adapted to the os magnum1 is horizontal1 broad and convex before1 narrow and concave behind2 the outermost facet is a small triangular surface inclined downwards to the level of the articulating surface of the outermost metacarpal4 ,it also presents a posterior vertical articular surface for a sesamoid bone4 ,the proximal extremity of the outer metacarpal bone is joined to the middle metacarpal1 not by one semilunar surface1 but by two separate articulations of small size 7fig4 #d and #e1 ,pl4 ,,xv472 it presents a single large slightly convex articular surface for the os magnum1 of an irregular semicircular form1 with the convexity of the curve turned outwards4 ,the metacarpus increases in breadth as it approaches the phalanges2 the two lateral metacarpals bending slightly away from the middle one1 and expanding towards their distal extremities3 the middle bone presents a symmetrical figure except at its proximal extremity 7fig4 #b1 ,pl4 ,,xi47 ,the distal articulating facet of each of the metacarpal bones extends so far upon both the anterior and posterior surfaces as to describe more than a semicircle 7fig4 #c1 ,pl4 ,,xi472 in the two lateral metacarpals it is traversed throughout by a longitudinal convex ridge dividing it into two equal lateral parts2 the ridge is most produced on the posterior half of the joint 7fig4 #d1 ,pl4 ,,xi473 in the middle metacarpal this ridge subsides before it reaches the anterior part of the articular surface4 ,the proximal extremity of the middle proximal phalanx presents a posterior notch corresponding to the above partially developed ridge3 the proximal extremities of the lateral phalanges are traversed by a middle longitudinal depression1 and two lateral shallow concavities 7fig4 #f1 ,pl4 ,,xi472 but these are of such an extent as to be in contact with only a part of the convexity above1 which therefore was doubtless adapted to a sesamoid bone on each side of the longitudinal ridge4 ,the structure of the above described joints proves that the motion of the toe upon the metacarpus was much freer and more extensive than in the ,rhinoceros1 which is the only existing ,ungulate mammal which presents the tridactyle structure in the fore-foot4 ,in this species the metacarpo-phalangeal articulations exhibit only a slight trace of the longitudinal ridges and grooves which are confined to the posterior part of the joint2 these are more developed in the ,camelid2 but the ,hog and ,horse in this respect approach nearer to the ,macrauchene1 though the structure of the metacarpo-phalangeal joints in the ,hog falls far short of the compactness and strength combined with freedom of play in flexion and extension which distinguish those of the ,macrauchene4 ,the ,palotherium medium most resembles the ,macrauchene in the structure of the trochlear metacarpo-phalangeal joints2 but both in this species1#bc and the ,pal4 crassum#bd the articular surface at the distal end of the metacarpal is relatively narrower than in the ,macrauchenia2 moreover all the species of the extinct ,palothere differ from the ,macrauchene in the greater size and strength of the middle as compared with the lateral metacarpals4 ,the articulation at the distal extremity of the proximal phalanges 7fig4 #e1 ,pl4 ,,xi47 is simple1 and not divided into two pulleys by a longitudinal ridge2 it is slightly concave from side to side2 but in its extent upon the anterior and posterior surfaces of the bone indicates a freedom of flexion and extension of the toes1 which harmonizes with the structure of the joint above4 ,the proximal articulating surfaces of the second phalanges 7fig4 #g1 ,pl4 ,,xi47 corresponds of course to those to which they are adapted2 they are1 however1 characterized by sending upwards an obtuse process from the middle of their anterior margin4 ,the distal articulating surfaces 7fig4 #h1 ,pl4 ,,xi47 resemble those of the proximal phalanges1 but extend further upon the back part of the phalanx than the front1 indicating the more horizontal position of the second phalanges4 ,the last phalanx1 does not resemble the neatly defined ungulate phalanges of the ,ruminantia1 and ,solipedia1 but has the irregular form characteristic of those of the ,pachydermata4 ,it is wedge-shaped1 broader than it is long1 with a rugged surface1 except where it plays upon the distal end of the second phalanx1 where it is slightly concave in one direction1 and convex in the other1 7figs4 #g and #i1 ,pl4 ,,xi47 ,a portion of this phalanx extends backwards behind the articular surface1 as in the corresponding bone of the ,palothere and ,rhinoceros4 ,the femur of the ,macrauchenia 7fig4 #a1 ,pl4 ,,xii47 is full two feet in length1 and consequently longer than in any known ,camel or ,rhinoceros2 as compared with its transverse diameter it is much longer than the femur of the latter animal3 in the proportion of its breadth to its length1 and the expansion of its extremities as compared with the diameter of the shaft1 it more resembles that of the ,camel4 ,the femur of the ,giraffe deviates from that of the ,macrauchenia in the excessive expansion of its distal extremity4 ,but the most striking evidence deducible from this bone1 of the affinity of the ,macrauchenia to the true ,pachydermatous type is afforded by the evident traces of a third trochanter1 the outline of which is conjecturally restored in the figure4 ,of the ,pachyderms which have this characteristic structure1 the extinct ,palothere offers the nearest resemblance to the ,macrauchene in the general form and structure of the femur4 ,the head of the femur in the ,macrauchene 7fig4 #b1 ,pl4 ,,xii47 presents the form of a pretty regular hemisphere2 it is less flattened above1 and is directed more obliquely inwards than in the ,palothere3 the neck supporting it does not project so far from the shaft as in the ,palothere or ,tapir1 but farther than in the ,camel4 ,the great trochanter rises above the level of the head2 in which structure and in the depression between the head and trochanter1 the femur of the ,macrauchene offers a character intermediate between the ,tapir or ,palothere1 and the ,camel4 ,the lesser trochanter is a slight projection from a ridge of bone which is continued from the under part of the head of the femur to the inner surface of the shaft4 ,in the ,palothere the lesser trochanter is situated more towards the posterior surface of the femur2 so that1 in this particular1 the ,macrauchene approaches nearer to the ,camel4 ,cuvier makes no mention of the condition of the depression for the ligamentum teres in the ,palothere4 ,among existing ordinary ,pachyderms the ,hippopotamus presents no trace of the insertion of a ligamentum teres in the head of the femur2 in the ,camel the place of its insertion is indicated by a well-marked circumscribed pit2 in the ,tapir a similar circular depression is situated close to the inferior margin of the articular convexity4 ,the ligament was undoubtedly present in ,macrauchenia1 but the place of its insertion is a broad and deep notch leading from the under and back part of the head of the bone a little way into its articular surface3 this ,i regard as another of those interesting transitional structures with which the remains of the ,macrauchenia1 few and imperfect though they unfortunately are1 so freely abound4 ,the femur of ,macrauchenia1 in the flatness of the back part of its neck1 and the elongated form of the post-trochanterian depression1 resembles that of the ,camel rather than that of the ,palothere2 and the same resemblance is shown in the cylindrical figure1 straightness1 and length of the shaft4 ,the depth of the trochanterian depression1 and the incurvation of the strong ridge continued downwards from the great trochanter are individual peculiarities in the ,macrauchenia4 ,a great part of the third trochanter is broken off2 but from the remains of its base we see that it had the same relative size as in the ,palothere2 but it is situated at the middle of the shaft of the femur1 and consequently lower down than in the ,palotheres and ,tapirs4 ,in the general form and relative size of the condyles at the distal extremity of the femur 7fig4 #c1 ,pl4 ,,ix4 and ,,xii47 the ,macrauchene is intermediate to the ,camel and ,palothere1 but resembles more the latter4 ,in the articular surface for the patella1 it deviates somewhat from the ,palothere1 having this part longer in proportion to its breadth1 more regularly and deeply concave from side to side1 and with its lateral boundaries more sharply defined4 ,in all these points the ,macrauchene approaches the ,camel3 the same affinity is shown in the protuberance above the inner condyle2 but in the extent of the posterior projection of this condyle 7fig4 #c1 ,pl4 ,,ix47 it exceeds the ,camel and ,palothere1 and displays an intermediate structure between these species and the ,hippopotamus4 ,there is a rough crescentic depression above the outer condyle where the linea aspera begins to diverge2 the corresponding depression is deeper in the ,hippopotamus1 while in the ,camel it is represented by a roughened surface only1 which is not depressed4 ,in the fossa between the rotular articulation and the external condyle the ,macrauchene resembles the ,camel3 the interspace of the condyles is relatively wider than in the ,camel1 and the process above the inner condyle is more angular2 in both these respects the ,macrauchene inclines towards the ,palothere4 ,in the structure of the bones of the leg of the ,macrauchenia we find the same transitional character which is afforded by the definable limits of the anchylosed bones of the fore-arm4 ,in the ,pachyderma the fibula is an entire and distinct bone4 ,in the ,ruminantia1 with the exception of the small ,musk-deer1 and1 in an inferior degree1 the ,elk1 the fibula appears only as a short continuous process sent down from the under part of the external condyle of the tibia4 ,in the ,camel tribe the only trace of the fibula in the bones of the leg1 is this process in a still more rudimental state4 ,in the ,macrauchenia the fibula is entire1 but is confluent with the tibia through nearly its whole extent3 the proximal part of the fibula is well defined2 its head is anchylosed to the outer condyle of the tibia1 but the shaft is continued free for the extent of nearly two inches1 and then again becomes confluent with the tibia1 forming apparently the outer ridge of that bone4 ,about five inches from the distal end of the tibia this outer ridge becomes flattened by being1 as it were1 pressed against the tibia1 and the anterior and posterior edges are raised above the level of the tibia2 beyond this part the limits of the fibula begin again to be defined by deep vascular grooves4 ,the outer side of the distal end of the fibula is excavated by a broad tendinous groove4 ,the fibula and tibia are distinct bones in both the ,palothere and ,anoplothere1 as in the ,pachyderms4 ,it is to the former genus1 however1 especially ,pal4 magnum1 that the ,macrauchene presents the nearest approach in the general form of the tibia1 the principal bone of its leg3 but in the ,macrauchene the tibia is relatively shorter1 and thicker1 and is straighter and less expanded at its extremities1 especially the upper one1 than in any of the ,palotheres4 ,the mesial boundaries of the two superior articulating surfaces of the tibia are raised in the form of ridges1 which are separated by a deep groove2 of these ridges the external is the highest1 as in ,pal4 magnum3 but the articular surfaces in the ,macrauchene slope away from these ridges more than in the ,palotheres4 ,the rotular or anterior tuberosity of the tibia is more produced1 and rises higher than in the ,palotheres2 the ridge continued downwards from this process is more marked in the ,macrauchene1 and its limits are better defined3 the shaft of the tibia below the ridge is also more flattened in the antero-posterior direction than in the ,palothere4 ,the configuration of the back part of both proximal and distal extremities of the tibia are so clearly and accurately given in figures #b and #c1 ,pl4 ,,xiii41 as to render verbal description unnecessary4 ,neither the text nor the figures in the #8,ossemens ,fossiles' afford the means of pursuing the comparison between the ,macrauchene and ,palothere in these particulars2 and ,i proceed1 therefore1 to the consideration of the inferior articulating surface of the bones of the leg 7fig4 #d1 ,pl4 ,,xiii47 ,since1 of the hind-foot1 we possess in the present collection only a single tarsal and metatarsal bone1 the structure of the distal articular surface of the tibia is attended with peculiar interest1 because we are taught by ,cuvier that it reveals to us in the ,ungulate animals the didactyle or tridactyle structure of the foot4 ,in the ,ruminants this articular surface is nearly square1 and extended transversely between two perpendicular malleoli1 while in the ,pachyderms with three toes to the hind-foot the articular surface of the tibia is oblique1 and is divided into two facets between the perpendicular malleolar boundaries4 ,now in the ,macrauchenia1 although the two bones of the leg are anchylosed together1 the extent of that part of the tarsal articular surface which is due to the tibia is indicated1 as in the case of the radius in the joint of the fore-arm1 by a groove2 and we are thus able to compare this surface with the distal articular surface of the tibia in the ,palothere and ,anoplothere4 ,it presents in the ,macrauchenia a very close resemblance with that of the ,palotherium magnum1#be being divided into two facets by a convex rising1 which traverses the joint from behind forwards2 but the ridge is narrower1 the internal facet somewhat deeper1 and the external oblique surface rather flatter than in the three-toed ,palothere4 ,in the portion of the tarsal articular surface due to the fibula1 we find1 however1 a more marked deviation from the ,palothere1 and an interesting correspondence with the ,anoplothere1 in the inferior truncation and horizontal articular surface which is continued upon the lower extremity of the fibula1 at right angles with the vertical malleolar facet which forms the outer boundary of the trochlea of the astragalus3 this articular surface unerringly indicates a corresponding articular projection in the calcaneum1 which1 therefore1 although the bone itself does not form part of the present collection1 we may conclude to differ from the calcaneum of the ,palotherium1 and to resemble that of the ,anoplotherium1 in this particular at least4 ,the valuable indication which the distal articular surfaces of the anchylosed tibia and fibula have given of the correspondence of the hind-foot with the fore-foot of the ,macrauchenia1 in regard to the number of the toes1 receives ample confirmation from the astragalus1 which1 of all the bones in the foot1 is the one that an anatomist would have chosen1 had his choice been so limited1 and which most fortunately has been secured by ,mr4 ,darwin1 in a very perfect state1 in the present instance4 ,i have compared this astragalus with that of the ,giraffe1 and other ,ruminants1 the ,camel1 the ,anoplothere1 the ,horse1 the ,hog1 the ,hippopotamus1 ,rhinoceros1 ,tapir1 and ,palothere3 it is with the ,pachyderms having three toes to the hind-foot1 that the ,macrauchenia agrees in the main distinguishing characters of this bone2 its anterior articular surface1 for example1 is simple1 and not divided into a double trochlea by a vertical ridge3 lastly1 it is with the astragalus of the ,tapir and ,palothere that it presents the closest correspondence in the general form and the minor details of structure1 and with these ,pachyderms1 therefore1 ,i shall chiefly limit the comparison of the ,macrauchenia1 in regard to the bone in question4 ,if the upper or tibial articular surface 7fig4 #e1 ,pl4 ,,xiv47 be compared with that in the ,palotherium magnum 7,ossem4 ,foss4 ,pl4 ,,liv4 fig4 #b17 it will be seen1 that the general direction of that surface is more parallel with the axis of the bone in ,macrauchenia4 ,in the ,palotherium it is turned a little towards the outer or fibular side1 and in the ,tapir the general direction of the same surface is placed still more obliquely4 ,the anterior border of this articulating surface is broken by a semicircular notch in the ,palothere2 in the ,tapir it describes a gentle concave curve1 and the ,macrauchene resembles the ,tapir in this respect4 ,the chief difference between the astragalus of the ,tapir and the ,palothere1 when viewed from above1 obtains in the relative length of the bone1 anterior to the tibial articulating surface3 the ,macrauchene presents1 in this respect1 an intermediate structure1 but differs from both in the greater extent of the tibial side of this part of the astragalus4 ,if we next direct attention to the anterior or scaphoid articular surface1 7fig4 #c1 ,pl4 ,,xiv47 and compare it with that of the ,palotherium magnum1 7fig4 #d1 ,pl4 ,,liv1 ,ossem4 ,foss47 it will be seen1 that it presents in the ,macrauchenia an oval1 and in the ,palotherium an irregular quadrangular form3 in the ,macrauchenia1 this surface is uniform or undivided1 and is gently convex1 except at its lower part2 while in the ,palothere it is divided by an oblique ridge into a broad internal facet for the scaphoid bone1 and a narrow internal surface for articulation with the os cuboides2 the larger surface is also concave transversely1 and slightly convex vertically3 in the ,tapir1 the anterior surface of the astragalus deviates still further from that of the ,macrauchenia1 both in general form1 and in the proportion of the cuboidal facet4 ,in the didactyle ,anoplotherium1 ,camel1 and true ,ruminants1 where the cuboides presents a large relative size1 a still greater proportion of the anterior surface of the astragalus is devoted to the articulation with this bone1 and is separated from the scaphoid surface by a well-developed vertical ridge4 ,the ,macrauchenia presents1 therefore1 the extreme variation from this type2--and should the entire tarsus hereafter be discovered1 it will doubtless be found1 that the os cuboides is articulated posteriorly to the os calcis exclusively4 ,the external surface of the astragalus of the ,macrauchene1 7fig4 #a4 ,pl4 ,,xiv17 is longer in proportion to its vertical extent than in the ,tapir or ,palothere3 the articular surface for the fibular malleolus is less curved4 ,between this surface and the anterior facet the bone is excavated by a deep notch1 both in the ,tapir and ,palothere2 but in the ,macrauchenia by a gentle concavity4 ,beneath the malleolar articular smooth surface in the ,palothere there is a deep pit2 in the ,tapir a shallow one2 but in the ,macrauchenia we observe only a smooth and slightly convex triangular surface4 ,if we compare the inner surface of the astragalus in these three animals1 we shall find the existing ,tapir again forming a transition between the two extinct genera4 ,in the ,palothere1 a round protuberance projects from the anterior part of this surface3 in the ,tapir1 we observe a gentle rising of the bone in the same part1 while in the ,macrauchene 7fig4 #b7 the surface of the bone is level at this part4 ,the margin of the tibial malleolar articular surface1 which is very slightly raised in the ,macrauchene1 is more developed in the ,tapir1 and still more so in the ,palothere1 where it forms a ridge1 overhanging the rough outer side of the bone4 ,near the lower part of this surface we observe a small but deep depression in the ,palothere2 there is a shallower one in the corresponding part in the ,tapir2 and the depression is still wider and shallower in the ,macrauchenia4 ,in the ,palothere the astragalus articulates by three surfaces with the os calcis1 posteriorly by a large concave surface1 externally by a longitudinal sub-elliptic surface1 and anteriorly by a thin transverse facet3 in the ,macrauchene 7fig4 #d7 two only of these surfaces are present1 viz4 the concave and the longitudinal one1 the anterior transverse surface being wanting3 in the ,tapir1 the transverse surface is present1 but is confluent with the longitudinal one4 ,the posterior surface is relatively larger and deeper in the ,macrauchene than in the ,palothere1 and approaches nearer to the triangular than the oval form3 the longitudinal surface is placed more obliquely1 and is truncated anteriorly4 ,in the ,tapir this surface is confluent with the scaphoid articular surface1 but it is separated therefrom by a narrow strip of bone in both the ,palothere and ,macrauchene4 ,it is satisfactory to find in the bone1 which marks most strongly the affinity of ,macrauchenia to ,palotherium1 so many easily recognizable differences1 because the structure of the cervical vertebr in the latter genus is too imperfectly known1 to allow us to predicate confidently a distinction between it and ,macrauchenia in that particular2 the difference1 however1 which they present in the condition of the bones of the fore-arm and leg1 forbids their being considered as generically related4 ,there remains to be noticed only a single fractured metatarsal bone 7fig4 #a4 ,pl4 ,,xv47 ,this1 from its bent and unsymmetrical figure1 is evidently not a middle one1 and having the side of the proximal end1 which was articulated to the adjoining metatarsal in a nearly perfect state1 it enables us to refer it with certainty to the hind-foot1 since it does not agree with any of the corresponding surfaces at the proximal extremities of the metacarpal bones4 ,it remains then to be determined1 whether it is an external metatarsal of the right-foot1 or an internal one of the left-foot1 the general curvature of these being in the same direction4 ,with neither of these bones in the ,tapir does our metatarsal agree1 since it has but one articular facet on the lateral surface of its proximal end1 while the outer metatarsal of the right-foot of the ,tapir1 with which1 in other respects1 it most closely corresponds1 has two articular surfaces4 ,in the cast of a hind-foot of a ,palothere1 ,i find that the outer metatarsal bone closely agrees with this metatarsal bone of the ,macrauchene1 in the structure just alluded to3 the articulation with the middle metatarsal being by a single sub-oval facet1 which stands out a little way from the surface of the bone3 the articular surface in the ,macrauchene presents a similar form and condition1 and is similarly situated to that in the ,palothere1 being at the posterior part of the lateral surface1 and a little below the superior or tarsal articular surface4 ,the bone expands towards its distal end1 which corresponds in structure with those of the two lateral metatarsals in the fore-foot1 in being completely divided into two trochlear surfaces by a well-developed median ridge1 and in having the posterior half of this ridge suddenly produced1 so as to project about two lines further from the trochlear surface than the anterior part of the same ridge4 ,in both the ,tapir and ,palothere this anterior part of the ridge is wholly suppressed1 and the posterior is much more feebly developed than in the ,macrauchenia4 ,the metatarsal bone here described is of exactly the same length with the internal metacarpal bone1 and proves1 in conjunction with the proportions of the astralagus1 that the fore and hind-feet of the ,macrauchenia were of equal size4 ,thus then we obtain evidence1 from a few mutilated bones of the trunk and extremities of a single representative of its race1 that there once existed in ,south ,america a ,pachydermatous quadruped1 not proboscidian1 which equalled in stature the ,rhinoceroses and ,hippopotamuses of the old world4 ,but this1 though an interesting and hitherto unsuspected fact1 is far from being the sum of the information which is yielded by these fossils4 ,we have seen that the single ungueal phalanx bespeaks a quadruped of the great series of ,ungulata1 and this indication is corroborated by the condition of the radius and ulna1 which are fixed immoveably in the prone position4 ,now in the ,ungulated series there are but two known genera1--the ,rhinoceros and ,palotherium1--which1 like the quadruped in question1 have only three toes on the fore-foot4 ,again1 in referring the ,macrauchenia to the ,tridactyle family of ,pachyderms1 we find1 towards the close of our analysis1 and by a detailed comparison of individual bones1 that the ,macrauchenia has the closest affinity to the ,palotherium4 ,but the ,palotherium1 like the ,rhinoceros and ,tapir1 has the ulna distinct from the radius1 and the fibula from the tibia2 so that even if the ,parisian ,pachyderm had actually presented the same peculiarities of the cervical vertebr as the ,patagonian one1 it would have been hazardous1 to say the least1 while ignorant of the dentition of the latter1 to refer it to the genus ,palotherium4 ,most interesting1 indeed will be the knowledge1 whenever the means of obtaining it may arrive1 of the structure of the skull and teeth in the ,macrauchenia4 ,meanwhile1 we cannot but recognise1 in the anchylosed and confluent state of the bones of the fore-arm and leg1 a marked tendency in it towards the ,ruminant ,order1 and the singular modifications of the cervical vertebr have enabled us to point out the precise family of that order1 with which the ,macrauchenia is more immediately allied4 ,in first demonstrating this relationship1 it was shown in how many particulars the ,camelid1 without losing the essential characters of ,ruminantia1 manifested a tendency to the ,pachydermatous type2 and the evidence which the lost genera1 ,macrauchenia and ,anoplotherium1 bear to a reciprocal transition from the ,pachyderms to the ,ruminants1 through the ,camelid1 cannot but be viewed with extreme interest by the ,zoologist engaged in the study of the natural affinities of the ,animal ,kingdom4 ,the ,macrauchenia is not less valuable to the ,geologist1 in reference to the geographical distribution of animal forms4 ,it is well known how unlooked-for and unlikely was the announcement of the existence of an extinct quadruped entombed in the ,paris ,basin1 whose closest affinities were to a genus1 7,tapirus17 at that time1 regarded as exclusively ,south ,american4 ,still greater surprise was excited when a species of the genus ,didelphys was discovered to have co-existed in ,europe with the ,palotherium4 ,now1 on the other hand1 we find in ,south ,america1 besides the ,tapir1 which is closely allied to the ,palothere1--and the ,llama1 to which the ,anoplothere offers many traces of affinity1--the remains of an extinct ,pachyderm1 nearly akin to the ,european genus ,palotherium3 and1 lastly1 this ,macrauchenia is itself in a remarkable degree a transitional form1 and manifests characters which connect it both with the ,tapir and the ,llama4 ,,admeasurements ,,of ,,the ,,bones ,,of ,,the ,,macrauchenia4 ,inches4 ,lines4 ,length of third 787 cervical vertebra #g #i ,vertical diameter of ditto #d #j ,vertical diameter of body of ditto #b #c ,transverse diameter of ditto #c #c ,vertical diameter of spinal canal #a ,length of fourth lumbar vertebra #e #e ,vertical diameter of body of ditto #b #i ,transverse diameter of ditto #b #aj ,vertical diameter of spinal canal #a #a ,transverse ditto ditto#bf #a #f ,transverse diameter of last lumbar vertebra #i ,transverse diameter of body of ditto #b #b ,vertical diameter of ditto #a #c ,entire length of lumbar region of vertebral column #bj ,vertical diameter of glenoid cavity of scapula #c ,transverse ditto ditto ditto #b #aj ,elevation of spine of scapula #c #e ,vertical diameter of proximal articular surface of fore-arm #c #f ,transverse ditto ditto ditto #c #e ,height of olecranon #e #c ,greatest diameter of its base #b ,circumference of proximal end of anchylosed radius and ulna #aa #aj ,entire length of inner toe of fore-foot1 inclusive of metacarpal bone #ac ,breadth of proximal end of metacarpus #c #h ,breadth of distal end of ditto #e #d ,length of inner metacarpal bone #g #f ,length of middle ditto #h ,length of outer ditto #g ,length of inner proximal phalanx #c #f ,length of middle ditto #b #aj ,length of outer ditto #c #d ,length of inner middle phalanx #b ,length of middle ditto #b #c ,length of inner distal phalanx#bg #a ,length of the femur #bd ,diameter of base of articular surface of the head of ditto #c #f ,greatest diameter of proximal end #g ,greatest diameter of distal end #f #c ,circumference of middle of shaft #h ,length of tibia #ah ,greatest diameter of proximal end #e #g ,greatest diameter of distal end1 including fibula #d #d ,circumference of middle of shaft #i ,length of metatarsal bone#bh #g #d ,,errata4--,the reader is requested to substitute the word #8right' for #8left' in the last line of p4 #ce1 before the words #8radius1' #8fore-foot1' and #8femur1' and in the first line of p4 #cf1 before the words #8tibia1' and #8hind-foot4' ,,description ,,of ,a ,,fragment ,,of ,a ,,cranium ,,of ,,an ,,extinct ,,mammal1 ,,indicative ,,of ,a ,,new ,,genus ,,of ,,edentata1 ,,and ,,for ,,which ,,is ,,proposed ,,the ,,name ,,of ,,glossotherium4 8,la premire chose faire dans l'tude d'un animal fossile1 est de reconnaitre la forme de ses dents molaires2 on dtermine par-l s'il est carnivore ou herbivore20 says ,cuvier1 at the commencement of that series of splendid chapters in which the restoration of the extinct ,pachyderms of the ,paris ,basin is recorded4 ,in the present case1 however1 as in that of the ,mammiferous animal whose fossil remains we were last considering1 the important organs1 to which ,cuvier directs our first attention1 are wanting4 ,nor are there here1 as in the ,macrauchenia1 any remains of the locomotive extremities to compensate for the deficiency of teeth1 and guide us into the right track of investigation and comparison4 ,the animal1 the nature and affinities of which are the subject of the following pages1 is1 in fact1 represented in ,mr4 ,darwin's collection1 by nothing more than a fragment of the cranium4 ,this fragment1 which was found in the bed of the same river1 7see p4 #af17 in ,banda ,oriental1 with the cranium of the ,toxodon1 includes the parietes of the left side of the cerebral cavity1 the corresponding nervous and vascular foramina1 the left occipital condyle1 a portion of the left zygomatic process1 and1 fortunately also1 the left articular surface for the lower jaw4 ,the importance of this surface in the determination of the affinities of a fossil animal has been duly appreciated1 since the relations of the motions of the lower jaw to the kind of life of each animal were pointed out by ,cuvier2 but yet we should be deceived were we to establish1 in conformity with the generalization enunciated by ,cuvier1#bi our conclusion1 from this surface1 of the nature of the food of the extinct species under consideration2 for the glenoid cavity is so shaped as to allow the lower jaw free motion in a horizontal plane1 from right to left1 and forwards or backwards1 like the movements of a mill-stone2 and1 nevertheless1 ,i venture to affirm it to be most probable1 that the food of ,glossotherium was derived from the animal and not from the vegetable kingdom2 and to predict1 that when the bones of the extremities shall be discovered1 they will prove the ,glossothere to be not an ungulate but an unguiculate quadruped1 with a fore-foot endowed with the movements of pronation and supination1 and armed with claws1 adapted to make a breach in the strong walls of the habitations of those insect-societies1 upon which there is good evidence in other parts of the present cranial fragment1 that the animal1 though as large as an ox1 was adapted to prey4 ,we perceive1 in the first place1 looking upon the base of this portion of skull1 a remarkable cavity1 situated immediately behind the tympanic bone1 of nearly a regular hemispherical form1 an inch in diameter 7fig4 #b1 b1 ,pl4 ,,xvi74 ,the superficies of this cavity appears not to have been covered with articular cartilage1 for it is irregularly pitted with many deep impressions2 and ,i conclude1 therefore1 that it served to afford a ligamentous attachment to the styloid element of a large os hyoides4 ,with this indication of the size of the skeleton of the tongue1 is combined a more certain proof of the extent of its soft1 and especially its muscular parts1 in the magnitude of the foramen1 for the passage of the lingual or motor nerve 7c4 fig4 #b and #c74 ,this foramen1 7the anterior condyloid17 in the present specimen1 is the largest of those which perforate the walls of the cranium1 with the exception of the foramen magnum2 it is fully twice the size of that which gives passage to the second division of the fifth nerve2 its area is oval1 and eight lines in the long diameter1 so that it readily admits the passage of the little finger4 ,it is only in the ,ant-eaters and ,pangolins that we find an approximation to these proportions of the foramen for the passage of the muscular nerve of the tongue2 and the existing ,myrmecophagous species even fall short of the larger fossil in this respect4 ,some idea of the size of the lingual nerve1 and of the organ it was destined to put in motion1 may be formed1 when it is stated that the foramen giving passage to the corresponding nerve in the ,giraffe1--the largest of the ,ruminants1 and having the longest and most muscular tongue in that order1--is scarcely more than one-fourth the size4 ,with these indications of the extraordinary development of the tongue1 we are naturally led1 in order to carry out a closer and more detailed comparison of the fossil in question1 to that group of mammalia in which the tongue plays the chief part in the acquisition of the food4 ,the size1 form1 and position of the occipital condyle1--the magnitude of the occipital foramen1 7which must here have somewhat exceeded three inches in the transverse diameter17--the slope of the occipital surface of the cranium from below1 upwards and forwards1 at an angle of #fj with the base of the cranial cavity-each and all attest the close affinities of the present animal to the ,edentata4 ,more decisive evidence of the same relationship will be adduced from the organization of other parts of the cranium4 ,the glenoid articular surface 7a1 fig4 #b1 ,pl4 ,,xvi47 is an almost flattened plane1 wider in the transverse than in the longitudinal direction2 and1 as in the genera ,myrmecophaga and ,manis1 it is not defended behind by any descending process4 ,in its general form it resembles the glenoid cavity of ,orycteropus more than that of the preceding ,edentates2 but1 in ,orycteropus1 the articulation is defended posteriorly by a descending process of the zygoma1 and it is also situated relatively closer to the os tympanicum4 ,had the ,glossotherium teeth8 ,the extent of the temporal muscle1 which is indicated by the rugged surface of the temporal fossa1 and by the well-marked boundary1 formed by a slightly elevated bony ridge1 which extends to near the line of the sagittal suture1 together with the size of the zygomatic portion of the temporal bone1 and the remains of the oblique suture by which it was articulated to the malar bone1 enables me to answer this question confidently in the affirmative4 ,they will probably be found to be molar teeth of a simple structure1 as in the ,orycteropus4 ,the evidence just alluded to of the existence of an os mal is interesting1 because this bone is wanting in the ,pangolins2 and its rudimental representative in the true ,ant-eaters does not reach the zygomatic process of the temporal bone1 which consequently has no articular or sutural surface at its anterior extremity4 ,in the presence1 therefore1 of the surface for the junction of the os mal1 and the consequent evidence of the completion of the zygomatic arch1 we learn that the ,glossothere was more nearly allied to the ,armadillos and ,orycterope4 ,that its affinity to the latter genus was closer than to the ,armadillos we have most interesting evidence in the form and loose condition of the tympanic bone3 it is represented of the natural size at fig4 #d1 ,pl4 ,,xvi4 ,through the care and attention devoted to his specimens by their gifted discoverer1 this bone was preserved in situ1 as represented at d1 fig4 #a2 but it had no osseous connection with the petrous or other elements of the temporal bone1 and could be displaced and replaced with the same ease as in the ,orycterope4 ,this bony frame of the membrana tympani1 in the ,glossothere1 describes rather more than a semicircle1 having the horns directed upwards2 it has a groove1 one line in breadth1 along its concave margin1 for the attachment of the ear-drum1 and sends down a rugged process1 half an inch long1 from its lower margin4 ,in the ,dasypodes and ,myrmecophag1 the tympanic bone soon becomes anchylosed with the other parts of the temporal2 it is only in ,orycteropus1 among the existing insectivorous ,bruta or ,edentata1 that it manifests throughout life the ftal condition of a distinct bony hoop1 deficient at the upper part4 ,the os tympanicum of ,orycteropus1 however1 differs from that of ,glossotherium1 in forming part of the circumference of an ellipse1 whose long axis is vertical2 and in sending outwards1 from its anterior part1 a convex eminence1 which terminates in a point directed downwards and forwards4 ,such appear to be the most characteristic features of the cranial fragment under consideration1 in which we have found1 that the articular surface for the os hyoides throws more light upon the nature of the animal of which it is a part1 than even the glenoid cavity itself4 ,there now remains to be described as much of the individual characters of the constituent bones as the specimen exhibits4 ,the occipital bone1 besides forming the posterior and part of the inferior parietes of the cranium1 extends for about half an inch upon the sides1 where the ex-occipital element is articulated by a vertical suture with the mastoid element of the temporal3 this suture is situated in a deep and well-marked muscular depression 7e1 fig4 #a71 measuring three inches in the vertical1 and upwards of one inch in the transverse direction4 ,the other sutures1 uniting the occipital to the adjoining bones1 are obliterated4 ,the breadth of the occipital region must have exceeded the height of the same by about one-third4 ,the condyle extends nearly to the external boundary of the occipital aspect of the cranium2 there is situated1 external to it1 only a small ovate1 rounded and smooth protuberance4 ,the slightly concave surface of the occipital plane of the cranium is bounded above by a thick obtuse ridge1 the muscular impressions are well sculptured upon it4 ,it is traversed transversely at its upper third by a slightly elevated bony crest2 and the surface below this ridge is again divided by a narrower intermuscular crest1 which runs nearly vertically1 at about an inch and a half from the external boundary of the occipital plane4 ,as a similar crest must have existed on the opposite side1 the general character of the occipital surface in the ,glossothere would resemble that of the ,toxodon4 ,a similar correspondence may be noticed in the terminal position of the condyle1 and the slope of the occipital plane4 ,above the transverse ridge1 the rough surface of the occipital plane slopes forward1 at a less obtuse angle with the basal plane1 to the first named ridge which separates the occipital from the coronal or superior surface of the skull4 ,the contour of this surface runs forwards1 as far as the fragment extends1 in an almost straight line3 the extent of surface between the temporal muscular ridges must have been about five inches posteriorly1 but it decreases gradually as it extends forwards3 all that part which is preserved is quite smooth4 ,the attachment of the fasciculi of the temporal muscle1 and the convergence of their fibres as they passed through the zygoma are well-marked on the sculptured surface of the bone4 ,the zygomatic process is relatively stouter than in ,orycteropus3 it is prismatic3 the external facet is nearly plane3 the superior is concave1 and increases in breadth anteriorly3 the inferior surface offers a slight convexity behind the flattened articular surface for the lower jaw4 ,the margin of the zygoma formed by the meeting of the upper and lower facets presents a semicircular curve1 extended transversely from the cranium1 and directed forwards4 ,the anterior extremity is obliquely truncated from below upwards and forwards1 and presents a flattened triangular surface indicative of its junction with an os mal3 the space between this extremity and the side of the cranium measures one inch and nine lines across1 and thus gives us the thickness of the temporal muscle4 ,the distance from the origin of the zygoma to the occipital plane is relatively greater than in ,orycteropus2 ,glossotherium is in this respect more similar to ,myrmecophaga and ,manis4 ,the sphenoid bone forms a somewhat smooth protuberance below and behind the base of the zygoma4 ,the tympanic bone is wedged in between this protuberance in front1 and the mastoid process behind4 ,the chief peculiarity of the broad mastoid is the regular semicircular cavity at its under part for the articulation of the styloid bone of the tongue4 ,this depression is separated below by a broad rough protuberance from the foramen jugulare1 7f1 fig4 #b1 ,pl4 ,,xvi17 which is immediately external to1 and slightly in advance of the great foramen condyloideum1 c4 ,a small rugged portion of the os petrosum separates the jugular from the carotid canal1 which arches upwards and directly inwards to the side of the shallow sella turcica1 7the external and internal orifices of the carotid canal are shown at g1 figs4 #b and #c74 ,the chief protuberance on the basis cranii is a large and rugged one1 serving for the attachment of muscles1 and due chiefly to the expansion of a great sinus in the body of the sphenoid4 ,this protuberance is separated from the smaller sphenoid protuberance before mentioned by a large groove continued downwards and forwards from the tympanic cavity1 and containing the ,eustachian tube1 which does not traverse a complete osseous canal4 ,immediately internal to the glenoid cavity is the large orifice of the canal transmitting the third division of the fifth pair of nerves1 the principal branch of which endows the tongue with sensibility2 this foramen 7h1 fig4 #b7 is rather less than that for the muscular nerve of the tongue4 ,the internal surface of the present cranial fragment affords a very satisfactory idea of the size and shape of the brain of the extinct species to which it belongs4 ,it is evident that1 as in other ,bruta1 the cerebellum must have been almost entirely exposed behind the cerebrum2 and that the latter was of small relative size1 not exceeding that of the ,ass2 and chiefly remarkable1 as in the ,orycterope1 ,ant-eater1 and ,armadillo for the great development of the olfactory ganglia4 ,the antero-posterior extent of the cribriform plate1 as exposed in this fragment1 is three inches1 and the complication of the thmoid olfactory lamell which radiate from it into the nasal cavity is equal to that which exists in the smaller ,edentata 7fig4 #c1 ,pl4 ,,xvi74 ,the nasal cavity is complicated in ,glossotherium by the great number and capacious size of the air-cells which are in communication with it3 these extend over all the upper1 lateral1 and back parts of the cranial cavity1 as far even as the upper boundary of the foramen magnum3 they also occupy the anterior two-thirds of the basis cranii4 ,the external configuration of the skull would1 therefore1 afford a very inadequate or rather deceptive notion of the capacity of the cerebral cavity1 were not the existence and magnitude of these sinuses known4 ,the interspace of the outer and inner tables of the cranium are separated above the origins of the olfactory ganglia for the extent of three inches3 above the middle of the cerebrum they are an inch and a half apart2 at the sides of the cranium the interposed air-cells are from one to two inches across2 at the back part of the cranium about one inch4 ,the sinuses have generally a rounded form4 ,the foramen rotundum1 7through which in figure #c a probe is represented as passing71 and the foramen ovale are situated close together1 within a common transversely oblong depression 7i74 ,the carotid canal 7g7 opens into the outer side of the commencement of this wide channel1 which conducts the great fifth pair of nerves to the outlets of its two chief divisions4 ,the petrous bone projects into the cranial cavity1 in the form of an angular process with three facets3 the foramen auditorium internum 7k71 and the aqueductus vestibuli1 are situated on the posterior facet4 ,immediately behind the os petrosum is the foramen lacerum jugulare 7l71 situated at the point of convergence of the vertical groove of the lateral sinus1 with a groove of similar size continued forwards from above the anterior condyloid canal4 ,the plane of the internal opening of this canal 7c1 fig4 #c7 is directed obliquely inwards and backwards1 and the lateral wall of the foramen magnum behind the foramen condyloideum slopes outwards to the edge of the condyle4 ,immediately internal to the foramen condyloideum is a small vascular foramen conducting a branch of the basilar artery into the condyloid canal1 for the nourishment1 doubtless1 of the great lingual nerve4 ,in the relations of the plane of the internal orifice of the anterior condyloid foramen with that of the foramen magnum1 we search in vain for a corresponding structure in any of the ,mammiferous orders1 save the ,edentata3#cj and among these the ,orycterope comes nearest the ,glossothere in this respect4 ,in the degree of development of the internal osseous ridge giving attachment to the tentorium cerebelli1 the ,ant-eaters and ,armadillos more resemble the ,glossothere than does the ,orycterope2 in which a continuous bony plate arches across the cranial cavity3 in the ,manis a still greater proportion of the tentorium is ossified1 and it consequently recedes the furthest amongst the ,edentata1 in this1 as in most other particulars of the cranial organization1 from the ,glossothere4 ,the chief distinctive peculiarity in the cranium of the ,glossothere1 so far as it can be studied in the present fragment1 and compared with that of other ,edentata1 is the deep1 well-marked1 semicircular styloid depression1 above described4 ,a question may arise after perusing the preceding evidence1 upon which the present fossil is referred to a great ,edentate species nearly allied to the ,orycteropus1 whether one or other of the lower jaws1 subsequently to be described1 and in like manner referable1 from their dentition1 either to the ,orycteropodoid or ,dasypodoid families of ,edentata1 may not have belonged to the same species as does the present mutilated cranium4 ,i can only answer1 that those jaws were discovered by ,mr4 ,darwin in a different and very remote locality1--that no fragments or teeth referable to them were found associated with the present fossil2 and that1 as it would be1 therefore1 impossible to determine from the evidence we have now before us1 which of the two lower jaws should be associated with ,glossotherium2 and as both may with equal if not greater probability belong to a totally distinct genus1 it appears to me to be preferable1 both in regard to the advancement of our knowledge of these most interesting ,edentata of an ancient world1 as well as for the convenience of their description1 to assign to them1 for the present1 distinct generic appellations4 ,the figures in ,plate ,,xvi4 preclude the necessity of a table of admeasurements of the cranial fragment of ,glossotherium4 ,,description ,,of ,a ,,mutilated ,,lower ,,jaw ,,and ,,teeth1 ,,on ,,which ,,is ,,founded ,a ,,subgenus ,,of ,,megatherioid ,,edentata1 ,,under ,,the ,,name ,,of ,,mylodon4 ,the genus ,megalonyx1 as is well known1 owes its name and the discovery of the fossil remains on which it was founded1 to the celebrated ,jefferson1#ca formerly ,president of the ,united ,states4 ,cuvier1 from an examination of a single tooth1 and the casts of certain bones of the extremities1 especially the terminal ones1 determined the ordinal affinities of this remarkable extinct quadruped4#cb ,but while he retained1 the name of ,megalonyx1 and used it in a generic sense1 ,cuvier offered no characters whereby other fossil remains might be generically either distinguished from1 or identified with the ,megalonyx ,jeffersonii1 unless1 among such remains there happened to be a tooth1 or a claw exactly corresponding with the descriptions and figures in the ,ossemens ,fossiles2 and when1 of course1 a specific identity1 and not merely a generic relationship would be established4 ,the greater part of ,cuvier's chapter on ,megalonyx is devoted to the beautiful and justly celebrated reasoning on the ungueal phalanx1 whereby it is proved to belong1 not to a gigantic ,carnivore of the ,lion-kind1 as ,jefferson supposed1 but to the less formidable order of ,edentate quadrupeds2 and ,cuvier1 in reference to the tooth1--the part on which alone a generic character could have been founded1--merely observes that it resembles at least as much the teeth of one of the great ,armadillos1 as it does those of the ,sloths4#cc ,in the last edition of the ,rgne ,animal1 ,cuvier introduces the ,megatherium and ,megalonyx1 between the ,sloths and ,armadillos2 but alludes to no other difference between the two genera than that of size1--8l'autre1 le ,megalonyx1 est un peu moindre40 7p4 #bbf47 ,some systematic naturalists1 as ,desmarest1 and ,fischer1 have1 therefore1 suppressed the genus1 and made the ,megalonyx a species of ,megatherium under the name of ,megatherium ,jeffersonii4 ,the dental characters of the genus ,megatherium are laid down by ,fischer#cd as follows3--8,dent4 prim1 et lan4 41 molar es 1 obducti1 tritores1 coronide nunc plan transversim sulcat nunc medio excavat marginibus prominulis40 ,that ,megalonyx had the same number of molares as ,megatherium1 7supposing that number in the ,megathere to be correctly stated1 which it is not17 is here assumed from analogy1 for neither ,jefferson1 ,wistar1 nor ,cuvier1--the authorities for ,megalonyx quoted by ,fischer--possessed other means of knowing the dentition of that animal than were afforded by the fragment of a single tooth4 ,now the almost entire lower jaw about to be described offers1 in so far as respects the general form and structure of the teeth1 the same kind and degree of correspondence with the ,megatherium1 as does the ,megalonyx ,jeffersonii of ,cuvier3 and1 what is only probable in that species1 is here certain1 viz41 an agreement with the ,megatherium in the class1 viz4 molares1 to which the teeth exclusively belong4 ,the question1 therefore1 on which ,i find myself1 in the outset1 called upon to come to a decision is1 as to the preference of the mode of viewing the subject of the generic relationship of the ,megalonyx adopted by ,desmarest1 ,fischer1 c41 or of that1 on which ,cuvier1 and after him ,dr4 ,harlan1 have practically acted3 whether1 in short1 the genus ,megatherium is to rest upon the more comprehensive characters of kind and general structure of the teeth1 or upon the more restricted ones1 of form and such modifications in the disposition and proportions of the component textures of the tooth1 as give rise to the characteristic appearances of the triturating surface of the crown4 ,with respect to existing ,mammalia1 most naturalists of the present day seem to be unanimous as to the convenience at least of founding a generic or subgeneric distinction on well-marked modifications in the form and structure of the teeth1 although they may correspond in number and kind1 in proof of which it needs only to peruse the pages of a ,systema ,mammalium which relate to the distribution of the ,rodent ,order4 ,according to this mode of viewing the logical abstractions under which species are grouped together1 the extinct ,edentate ,mammal discovered by ,jefferson must be referred to a genus distinct from ,megatherium1 and for which the term ,megalonyx should be retained4 ,this will be sufficiently evident by comparing the descriptions given by ,cuvier of one of the teeth of the ,megalonyx ,jeffersonii1 and by ,dr4 ,harlan of a tooth of his ,megalonyx laqueatus1 with those of the ,megatherium which have been published by ,mr4 ,clift4 ,the fragment of the molar tooth of the ,megalonyx ,jeffersonii1 described and figured in the ,ossemens ,fossiles1 seems to have been implanted in the jaw1 like the teeth of the ,megatherium1 by a simple hollow base similar in form and size to the protruded crown3 its structure ,cuvier describes as consisting of a central cylinder of bone enveloped in a sheath of enamel4#ce ,the transverse section of this tooth presents an irregular elliptical form1 the external contour being gently and uniformly convex1 the internal one1 undulating2 convex in the middle1 and slightly concave on each side1 arising from the tooth being traversed longitudinally on its inner side by two wide and shallow depressions4 ,the imperfect tooth of the species called by ,dr4 ,harlan ,megalonyx laqueatus1 and of which a cast was presented by that able and industrious naturalist to the ,museum of the ,royal ,college of ,surgeons1 resembles in general form1 and especially in the characteristic double longitudinal groove on the inner side1 the tooth of the ,megalonyx ,jeffersonii4 ,it is thus described by ,dr4 ,harlan3 8,the fractured molar tooth appears to have belonged to the inferior maxilla on the right side2 the crown is destroyed2 a part of the cavity of the root remains4 ,the body is compressed transversely1 and presents a double curvature1 which renders its anterior and exterior aspects slightly convex2 the posterior and interior gently concave2 these surfaces are all uniform1 with the exception of the interior or mesial aspect1 which presents a longitudinal rib or ridge1 one-half the thickness of the long diameter of the tooth2 with a broad1 not profound longitudinal groove or channel along each of its borders4 ,it is from this resemblance to a portion of a fluted column1 that the animal takes its specific appellation 7,megx4 laqueatus74 8,the crown would resemble an irregular ellipsis widest at the anterior portion4 ,the tooth consists of a central pillar of bone surrounded with enamel1 the former of a dead white1 the latter of a ferruginous brown colour3 the transverse diameter is more than two-thirds less than its length1 whilst that of ,megx4 ,jeffersonii is only one-third less--the antero-posterior diameter is one-half its length in the former1 and two-thirds less in the latter4 ,the proportions of this tooth are consequently totally at variance with that of its kindred species40 ,vide ,pl4 ,,xii4 fig4 #g1 #h1 #i4cf ,dr4 ,harlan describes also two claws of the fore-foot1 a radius1 humerus1 scapula1 one rib1 an os calcis1 a metacarpal bone1 certain vertebr1 a femur1 and tibia1 of the same ,megalonyx2 these parts of the skeleton1 together with the tooth1 which so fortunately served to establish the generic relationship of the species with the ,megalonyx of ,jefferson and ,cuvier1 were discovered in ,big-bone-cave1 ,tennessee1 ,united ,states4 ,dr4 ,harlan does not enter into the question of the generic characters of ,megalonyx1 but it would seem that he felt them to rest not entirely on dental modifications1 for he observes that 8a minute examination of the tooth and knee-joint renders it not improbable1 supposing the last named character to be peculiar to it1 that if the whole frame should hereafter be discovered1 it may even claim a generic distinction1 in which case1 either ,aulaxodon1 or ,,pleurodon1 would not be an inappropriate name40#cg ,there can be no doubt1 as it appears to me1 with respect to a fossil jaw presenting teeth in the same number1 and of the same general structure1 as in the ,megatherium1 and with individual modifications of form1 as well-marked as those which distinguish ,megatherium from ,megalonyx1 that the ,palontologist has no other choice than to refer it1 either as ,fischer has done with ,megalonyx1 to a distinct species of the genus ,megatherium1 or to regard it as the type of a subgenus distinct from both4 ,with reference1 however1 to the ,pleurodon of ,dr4 ,harlan1 after a detailed comparison of the cast of the tooth on which that genus is mainly founded1 with the descriptions and figures of the tooth of the ,megalonyx ,jeffersonii1 in the 8,ossemens ,fossiles10 they seem to differ in so slight a degree as to warrant only a specific distinction1 and this difference even1 viewing the various proportions of the teeth in the same jaw of the ,megatherium1 is more satisfactorily established by the characters pointed out by ,dr4 ,harlan in the form and proportions of the radius1 than by those in the tooth itself4 ,the next notice of the ,megalonyx which ,i have consulted1 in the hope of meeting with additional and more precise information as to its real generic characters1 is an account given by the learned ,professor ,doellinger1#ch of some fossil bones1 collected by the accomplished travellers ,spix and ,martius in the cave of ,lassa ,grande1 near the ,arrayal de ,torracigos1 in ,brazil4 ,in this collection1 however1 it unfortunately happens that there are no teeth1 but only a few bones of the extremities1 including some ungueal phalanges1 which ,professor ,doellinger concludes1 from their shape1 the presence of an osseous sheath for the claw1 and the form of their articulation1 to belong1 without doubt1 to an animal of the ,megatherioid kind1 about the size of an ,ox4 ,he particularly states that they are not bones of an immature individual2 but that they agree sufficiently with ,cuvier's descriptions and figures of the ,megalonyx to be referred to that species of animal 7zu dieses thierart27 and he adds1 what is certainly an interesting fact1 that the fossils in question form the first of the kind that had been discovered out of ,north ,america4 ,subsequently to the discovery of these bones1 and of those of the ,megalonyx laqueatus above alluded to1 the remains of another great ,edentate animal were found in ,north ,america1 and were deposited in the ,lyceum at ,new ,york2 among these is a portion of the lower jaw with the whole dental series of one side4 ,it is thus described by ,dr4 ,harlan4 8,the fragment ,i am now about to describe is a portion of the dexter lower jaw of the ,megalonyx1 containing four molar teeth2 three of the crowns of these teeth are perfect1 that of the anterior one is imperfect4 ,these teeth differ considerably from each other in shape1 and increase in size from the front1 the fourth and posterior tooth being double the size of the first1 and more compressed laterally2 it is also vertically concave on its external aspect1 and vertically convex on its internal aspect2 the interior or mesial surface is strongly fluted1 and it has a deep longitudinal furrow on the dermal aspect1 in which respect it differs from the tooth of the ,m4 laqueatus previously described by me1 of which the dermal aspect is uniform1 but to which1 in all other respects1 it has a close resemblance4 ,i suppose it therefore probable1 that this last may have belonged to the upper jaw4 ,the three anterior molars differ in shape and markings3 they are vertically grooved1 or fluted1 on their interior and posterior aspects1 a transverse section presenting an irregular cube4 ,the length of the crown of the posterior molar is two inches3 the breadth about five-tenths of an inch3 the length of the tooth is three inches and six-tenths4 ,the diameter of the penultimate molar is eight-tenths by seven-tenths of an inch4 ,the length of this fragment of the jaw-bone is eight inches and four-tenths2 the height three inches and six-tenths3 the length of the space occupied by the alveolar sockets five inches and eight-tenths4 ,the crown of the tooth presents no protuberances1 but resembles that of the ,sloth2 the roots are hollow40#ci ,this fossil is referred by ,dr4 ,harlan to his ,megalonyx laqueatus2 but1 pending the absence of other proof of the identity of species1 in which1 as may be seen by comparing fig4 #b1 with fig4 #d1 in ,pl4 ,,xvii41 the teeth differ widely in form1 it would be obviously hazardous to adopt such an approximation on hypothetical grounds4#dj ,in order1 however1 to obtain more satisfactory evidence of the nature and amount of the difference between the ,megalonyx laqueatus1 and the allied animal represented by the above-described fragment of lower jaw1 ,i wrote to my much respected friend ,m4 ,,laurillard1 requesting him to send me a sketch of the teeth in the cast of that lower jaw1 which had been transmitted from ,new ,york to the ,garden of ,plants4 ,with full confidence in the characteristic precision and accuracy of the drawing with which ,i have been obligingly favoured by ,m4 ,laurillard1 ,i am disposed to regard the amount of difference recognizable in every tooth in the lower jaw in question 7fig1 #c and #d17 as compared with the molar tooth either of ,megalonyx ,jeffersonii 7fig4 #a17 or ,megx4 laqueatus 7fig4 #b7 to be such as to justify its generic separation from ,megalonyx on the same grounds as ,megalonyx is distinguished from ,megatherium1 and for the subgenus of ,megatherioid ,edentata1 thus indicated1 ,i would propose the name of ,,mylodon4#da ,the species of which the fossil remains are described by ,dr4 ,harlan may be dedicated to that indefatigable ,naturalist who has contributed to natural science so much valuable information respecting the ,zoology1 both recent and fossil1 of the ,north ,american continent4 ,the fossil about to be described represents a second and smaller species of the same genus1 and ,i propose to call it ,mylodon ,darwinii1 in honour of its discoverer1 of whose researches in the ,southern division of the ,new ,world it forms one of many new and interesting fruits4 ,this fossil was discovered in a bed of partly consolidated gravel at the base of the cliff called ,punta ,alta1 at ,bahia ,blanca in ,northern ,patagonia3 it consists of the lower jaw with the series of teeth entire on both sides3 but the extremity of the symphysis1 the coronoid and condyloid processes1 and the angular process of the left ramus1 are wanting4 ,the teeth are composed1 as in ,bradypus1 ,megatherium and ,megalonyx1 of a central pillar of coarse ivory1 immediately invested with a thin layer of fine and dense ivory1 and the whole surrounded by a thick coating of cement4 ,in the fig4 #e1 ,pl4 ,,xvii41 the fine ivory is represented by the white striated concentric tract on the grinding surface of the teeth2 it is of a yellowish-white colour in the fossil1 and stands out1 as an obtuse ridge1 from that surface3 both these conditions depend on the large proportion of the mineral to the animal constituent in this substance of the tooth4 ,the external layer of the cement presents in the fossil the same yellowish-brown tint as the bone itself1 which it so closely resembles1 both in intimate structure and in chemical composition2 the internal layer next the dense ivory is jet black1 indicating the great proportion of animal matter originally present in this part4 ,the central pillar of coarse ivory1 which1 from its more yielding texture1 has been worn down into a hollow at the triturating surface of the tooth1 also presents1 as a consequence of the less proportion of the hardening phosphates1 a darker brown colour than the external layer of the cement1 or the bone itself4 ,the teeth are implanted in very deep sockets2 about one-sixth only of the last molar projects above the alveolus2 the proportion of the exposed part of the tooth increases as they are placed further forwards4 ,the implanted part of each tooth is simple2 preserving the same size and form as the projecting crown1 and presenting a large conical cavity at the base1 indicative of the original persistent pulp1 and perpetual growth of these teeth4 ,the extent of the whole four alveoli is four inches1 eight lines2 the length of the jaw from the angle to the broken end of the symphysis is seventeen inches and a half2#db from the figures it will be seen that only a small proportion of the anterior part of the jaw is lost1 so that we may regard the dentigerous part of the jaw as being limited to about one-fourth of its entire length2 the alveoli being nearly equidistant from the two extremities4 ,the first and second teeth1 counting backwards1 are separated by an interspace of rather more than three lines2 that between the second and third is one line less2 the third and fourth are rather more than a line apart3 from the oblique position1 however1 of the three hinder teeth the intervals between them appear in a side view1 as in fig4 #a1 ,pl4 ,,xix41 to be less than in reality1 and the third and fourth teeth seem to touch each other4 ,each tooth has a form and size peculiar to itself1 and different from the rest1 but corresponds of course with its fellow on the opposite side4 ,the same may be observed1 but in a less degree1 in the teeth of the ,megatherium itself2 hence1 it is obviously hazardous to found a generic distinction upon a single tooth1 unless1 as in the case of the ,glyptodon1#dc the modification of form happens to be extremely well-marked4 ,the whole series of teeth1 or their sockets1 at least of one of the jaws1 should be known for the purpose of making a satisfactory comparison with the previously established ,edentate genera4 ,the first molar in the present jaw is the smallest and simplest of the series3 its transverse section is ellipsoid1 or subovate1 narrowest in front1 and somewhat more convex on the outer than on the inner side3 the long diameter of the ellipse is nine lines1 the short or transverse diameter six lines3 the length of the tooth may be about three inches1 but ,i have not deemed it necessary to fracture the alveolus in order to ascertain precisely this point4 ,the second tooth presents in transverse section a more irregular and wider oval figure than the first3 the line of the outer side is convex1 but that of the inner side slightly concave1 in consequence of the tooth being traversed longitudinally by a broad and shallow channel or impression2 the longitudinal diameter of the transverse section is one inch2 the transverse diameter at the widest part nine lines4 ,there is a slight difference in the size of this tooth on the two sides of the jaw1 the right one1 from which the above dimensions are taken1 being the largest4 ,the transverse section of the third tooth has a trapezoidal or rhomboidal form2 the angles are rounded off2 the posterior one is most produced2 the anterior and posterior surfaces are flattened1 the latter slightly concave in the middle2 the external and internal sides are concave in the middle1 especially the inner side1 where the concavity approaches to the form of an entering notch4 ,the longest diameter of the transverse section of this tooth is thirteen lines1 the shortest seven lines and a half3 in the tooth on the right side the external surface is nearly flat2 this slight difference is not indicated in the figure 7,pl4 ,,xviii47 ,the last molar1 which is generally the most characteristic in the fossil ,bruta1 presents in an exaggerated degree the peculiarities of the preceding tooth2 the longitudinal channels on both the outer and inner surfaces encroach so far upon the substance of the tooth1 that the central coarse ivory substance is as it were squeezed out of the interspace1 and the elevated ridge of the dense ivory describes an hour-glass figure upon the triturating surface1 the connecting isthmus being but half the breadth of the rest of the tract2 the external cmentum preserves nearly an equal thickness throughout4 ,of the two lobes into which this tooth is divided by the transverse constriction1 the anterior is the largest2 their proportions and oblique position are pretty accurately given in the figure4 ,the longitudinal diameter of the transverse section of this tooth is one inch1 seven lines1 its greatest lateral or transverse diameter is ten lines1 its least diameter at the constricted part is three lines1 the length of the entire tooth is four inches4 ,judging from the form of the jaw1 the length of the other teeth decreases in a regular ratio to the anterior one4 ,the posterior tooth is slightly curved1 as shown in fig4 #b1 ,pl4 ,,xix41 with the concavity directed towards the outer side of the jaw4 ,the general form of the horizontal ramus of the jaw1 is so well illustrated in the figures ,pl4 ,,xviii4 and ,,xix41 that the description may be brief4 ,the symphysis is completely anchylosed1 about four inches in length1 and extended forward to the extremity of the jaw at a very slight angle with the inferior border of the ramus3 it is of great breadth1 smooth and gently concave internally1 and suggests the idea of its adaptation for the support and gliding movements forwards and backwards of the free extremity of a long and well-developed tongue4 ,the exterior surface of the symphysis is characterized by the presence of two oval mammilloid processes1 situated on each side of the middle line1 and about half-way between the anterior and posterior extremes of the symphysis4 ,a front view of these processes1 of the natural size1 is given in fig4 #d1 ,pl4 ,,xix43 a side view of the one on the right side represented in the reduced figure4 ,nearly four inches behind the anterior extremity of the above process is the large anterior opening of the dental canal3 it is five lines in diameter1 situated about one-third of the depth of the ramus of the jaw from the upper margin4 ,the magnitude of this foramen1 which gives passage to the nerve and artery of the lower lip1 indicates that this part was of large size2 and the two symphyseal processes1 which probably were subservient to the attachment of large retractor muscles1 denote the free and extensive motions of such a lip1 as we have presumed to have existed from the size of the foramina destined for the transmission of its nervous and nutrient organs4 ,the angle of the jaw is produced backwards1 and ends in an obtuse point1 slightly bent upwards2 a foramen1 one-third less than the anterior one1 leads from near the commencement of the dental canal1 to the outer surface of the jaw1 a little below and behind the last molar tooth2 this foramen presents the same size and relative position on both sides of the jaw4 ,i find no indication of a corresponding foramen1 or of symphyseal processes in the figures or descriptions of the lower jaw of the ,megatherium1 nor in the lower jaw of the ,sloths1 ,ant-eaters1 ,armadillos1 or ,manises1 which ,i have had the opportunity of examining with a view to this comparison4 ,in the ,megatherium the inferior contour of the lower jaw is peculiarly remarkable1 as ,cuvier has observed1 for the convex prominence or enlargement which is developed downwards from its middle part4 ,in the ,mylodon the corresponding convexity exists in a very slight degree1 not exceeding that which may be observed at the corresponding part of the lower jaw of the ,ai1 or ,orycterope4 ,a broad and shallow furrow extends along the outer side of the jaw1 close to the alveolar margin1 from the beginning of the coronoid process to the anterior dental foramen4 ,the base of the coronoid process begins external and posterior to the last grinder3 the whole of the ascending ramus of the jaw1 beneath the coronoid process is excavated on its inner side by a wide and deep concavity1 bounded below by a well-marked ridge1 which extends obliquely backwards from the posterior part of the alveolus of the last grinder to the inferior margin of the ascending ramus1 which is bent inwards before it reaches the angle of the jaw4 ,the large foramen or entry to the dental canal is situated in the internal concavity of the ascending ramus of the jaw1 two inches behind the last molar1 three inches from the lower margin of the ramus1 and nearly five inches from the elevated angle of the jaw3 it measures nine lines in the vertical diameter1 and its magnitude indicates the large size of the vessels which are destined to supply the materials for the constant renewal of the dental substance1--a substance which from its texture must be supposed to have been subject to rapid abrasion4 ,about an inch behind the dental foramen a deep vascular groove1 about two lines in breadth1 is continued downwards to the ridge which circumscribes the internal concavity of this part of the jaw1 and perforates the ridge1 which thus arches over the canal3 this structure is present in both rami of the jaw4 ,the mylo-hyoid ridge is distinctly marked about an inch and a half below the alveolar margin4 ,other muscular ridges and irregular eminences are present on the outer side of the base of the ascending ramus1 and near the angle of the jaw2 as shown in fig4 #a1 ,pl4 ,,xix4 ,from the preceding descriptions it will be seen that the lower jaw of the ,mylodon is very different from that of the ,megatherium2 with that of the ,megalonyx we have at present no means of comparing it4 ,among existing ,edentata the ,mylodon1 in the form of the posterior part and angle of the jaw1 holds an intermediate place between the ,ai and the great ,armadillo2 in the form of the anchylosed symphysis of the lower jaw it resembles most closely the ,unau or two-toed ,sloth2 but in the peculiar external configuration of the symphysis resulting from the mammilloid processes above described1 the ,mylodon presents a character which has not hitherto been observed in any other species of ,bruta1 either recent or fossil4 ,in conclusion it may be stated1 that the teeth and bones here described offer all the conditions and appearances of those of a full grown animal2 and that they present a marked difference of size as compared with those of the ,mylodon ,harlani1 as will be evident by the following admeasurements4 ,,admeasurements ,,of ,,the ,,lower ,,jaw ,,of ,,mylodon ,,darwinii4 ,inches4 ,lines4 ,length 7as far as complete7 #ag #f ,extreme width1 from the outside of one ramus to that of the other #i #j ,depth of each ramus #d #i ,length of alveolar series #d #h ,from first molar to broken end of symphysis #f #j ,breadth of symphysis #c #g ,longitudinal extent of symphysis #d #f ,circumference of narrowest part of each ramus #e #i ,,description ,,of ,a ,,considerable ,,part ,,of ,,the ,,skeleton ,,of ,a ,,large ,,edentate ,,mammal1 ,,allied ,,to ,,the ,,megatherium ,,and ,,orycteropus1 ,,and ,,for ,,which ,,is ,,proposed ,,the ,,name ,,of ,,scelidotherium#dd ,,leptocephalum4 ,of the large ,edentate quadrupeds that once existed in the ,new ,world1 sufficient of the osseous remains of the gigantic ,megatherium alone has been transmitted to ,europe to give a satisfactory idea of the general form and proportions of the extinct animal4 ,different bones of the ,megalonyx1 ,mylodon1 and ,glyptodon have been described1 but not sufficient of the remains of any individual of these subgenera has1 hitherto1 reached ,europe1 or been so described as to enable us to form a comparison between them and the ,megatherium1 or any of the existing ,edentata1 in regard to the general construction and proportions of the entire skeleton4 ,this state of our knowledge of the osteology of the singular giants of the ,edentate ,order renders the remains of the present animal peculiarly interesting1 since1 although the extremities are too imperfect to enable us to reconstruct the entire skeleton1 a sufficient proportion of it has been preserved in the natural position to give a very satisfactory idea of its affinities to other ,edentata1 whose osteology is more completely known4 ,the fossil remains here described were discovered by ,mr4 ,darwin in the same bed of partly consolidated gravel at ,punta ,alta1 ,northern ,patagonia1 as that in which the lower jaws of the ,toxodon and ,mylodon were imbedded4 ,the parts of the skeleton about to be described were discovered in their natural relative position1 as represented at ,pl4 ,,xx41 indicating1 ,mr4 ,darwin observes1 that the sublittoral formation in which they had been originally deposited had been subject to little disturbance4#de ,they include the cranium1 nearly entire1 with the teeth and part of the os hyoides2 the seven cervical1 eight of the dorsal1 and five of the sacral vertebr1 the two scapul1 left humerus1 radius and ulna1 two carpal bones1 and an ungueal phalanx2 both femora1 the proximal extremities of the left tibia and fibula1 and the left astragalus4 ,the principal parts of the cranium which are deficient are the anterior extremities of both the upper and lower jaws1 the os frontis1 thmoid bone1 and the whole upper part of the facial division of the skull2 but sufficient remains to show that the general form of the skull resembled an elongated1 slender1 subcompressed cone1 commencing behind by a flattened vertical base1 slightly expanding to the zygomatic region1 and thence gradually contracting in all its dimensions to the anterior extremity4 ,the ,cape ,ant-eater 7,orycteropus71 of all ,edentata1 most nearly resembles the present fossil in the form of its cranium1 and next in this comparison the great ,armadillo 7,dasypus gigas1 ,cuv47 may be cited3 on the supposition1 therefore1 that the correspondence with the above existing ,edentals observable in the parts of the fossil cranium which do exist1 was carried out through those which are defective1 the length of the skull of the ,scelidothere must have been not less than two feet4 ,if now the reader will turn to ,pl4 ,,xx4 he will see that this cranium is singularly small and slender in proportion to the rest of the skeleton1 especially the bulky pelvis and femur1 of which bones the latter has a length of seventeen inches1 and a breadth of not less than nine inches2 the astragalus1 again1 exceeds in bulk that of the largest ,hippopotamus or ,rhinoceros2 yet the condition of the epiphyseal extremities of the long bones proves the present fossils to have belonged to an immature animal4 ,hence1 although the ,scelidothere1 like most other ,edentals1 was of low stature1 and1 like the ,megatherium1 presented a disproportionate development of the hinder parts1 it is probable1 that1 bulk for bulk1 it equalled1 when alive1 the largest existing pachyderms1 not proboscidian4 ,there is no evidence that it possessed a tesselated osseous coat of mail4 ,i shall commence the description of the present skeleton with the cranium4 ,the condyles of the occiput 7,see ,pl4 ,,xxi4 fig4 #b17 are wide apart1 sub-elliptic1 very similar in position1 form1 and relative size to those in ,orycteropus4 ,the foramen occipitale is transversely oval1 its plane slopes from above downwards and forwards at an angle of #dj with that of the occipital region of the skull4 ,this region1 as before stated1 is vertical in position 7see fig4 #a1 ,pl4 ,,xxi471 of a sub-semicircular form1 the breadth being nearly one-third more than the height2 it is bounded above and laterally by a pretty regular curve2 but the superior margin is not produced so far backwards as in ,orycteropus4 ,the occipital plane is bisected by a mesial vertical ridge2 there is a less developed transverse curved intermuscular crest which runs parallel with and about half an inch below the marginal ridge3 the surface of the occipital plane on the interspaces of these ridges is irregularly pitted with the impression of the insertion of powerful muscles4 ,the corresponding surface is smooth in the ,orycterope and ,armadillos2 in the great extinct ,glossothere it resembles in character that of the ,scelidothere2 but in the forward slope of the occipital plane the ,glossothere differs in a marked degree from the present animal4 ,the upper surface of the cranium is smooth and regularly convex4 ,the extent of the origin of the temporal muscles is defined by a slightly-raised broad commencement of a ridge1 which1 in the older animal1 might become more developed4 ,there is no trace of this ridge in the ,orycterope2 but it exists in the ,armadillos1 in which the teeth are of a denser texture1 and better organized for mastication1 and consequently are associated with better developed masticatory muscles4 ,it will be subsequently shown that the ,scelidothere resembles the ,armadillos in so far as it possesses a greater proportion of the dense ivory to the external cmentum in its teeth1 than does the ,megatherium2 while it differs widely from the ,orycterope1 in the structure of its teeth4 ,the teeth1 however1 are fewer in the ,scelidothere than in any ,armadillo1 and relatively smaller than in most of the species of that family4 ,accordingly we find that the zygomatic arches are relatively weaker2 and in this particular the ,scelidothere corresponds with the ,orycterope4 ,the zygomatic process of the temporal commences posteriorly about an inch and a half from the occipital plane1 its origin or base is extended forwards in a horizontal line fully four inches1 where it terminates as usual in a thin concave edge1 as shown on the right side in ,pl4 ,,xxii4 ,the free portion of the zygoma1 continued forwards from the outer part of this edge1 is a slender sub compressed process1 half an inch in the longest or vertical diameter1 and less than three lines in the transverse2 the extremity of this process is broken off2 the opposite extremity of the malar portion of the zygoma is entire1 and obtusely rounded4 ,the bony arch may have been completed by the extension of the temporal process to the malar one1 but the two parts undoubtedly were not connected together by so extensive a surface as in the ,orycterope4 ,on the other hand1 if the zygomatic arch be naturally incomplete in the ,scelidothere1 the interspace between the malar and temporal portions must be relatively much less than in the ,sloth or ,ant-eater2 for the broken end of the temporal part is separated from the obtusely rounded apex of the malar process in the present specimen by an interval of only one inch4 ,the articular surface 7,pl4 ,,xxiii41 fig4 #b7 beneath the zygoma for the lower jaw is flat and even1 with the outer and inner margin slightly bent down1 but having no definable anterior or posterior limits2 its breadth is two inches4 ,it differs from the corresponding surface in the ,orycterope in being separated by a relatively wider interval from the tympanic bone1 and in wanting consequently the support which the bony meatus auditorius gives in the ,orycterope to the back part of the mandibular joint4 ,the ,armadillos differ still more from the ,scelidothere in this important part of the cranial organization1 inasmuch as the glenoid cavity is not only protected behind by the descending os tympanicum1 but also in front by a corresponding vertical downward extension of the os mal4 ,the ,scelidothere in the general form and relative position of the surface for the articulation of the lower jaw resembles the ,glossothere more closely than any other ,edentate animal with which ,i have been able to compare it4 ,the malar bone of the ,megatherium presents1 as is well known1 two characters1 in which it conspicuously differs from that of the ,orycterope and ,armadillos1 and approximates in an equally marked degree to the ,sloths2 these characters consist in a process ascending as if to complete the posterior circumference of the orbit1 and another process descending outside the lower jaw to give advantageous and augmented surface of attachment to the masseteric muscle1 in its character of a protractor of the jaw4 ,now both these modifications of the malar bone are present in the ,scelidothere1 and are the chief if not the sole marks of the affinity to the ,megatherium which the structure of the cranium affords4 ,they are1 however1 the more interesting1 perhaps1 on that account1 and because they are associated with other and more numerous characters approximating the species in question to the ordinary terrestrial as distinguished from the arboreal ,edentata4 ,for if the ,scelidothere1 instead of the ,megathere1 had been discovered half a century ago1 and if its true nature and affinities had been in like manner elucidated by the genius and science of a ,cuvier2 and supposing on the other hand that the ,megatherium instead of the ,scelidothere had been one of the novel and interesting fruits of ,mr4 ,darwin's recent exploration of the coast of ,south ,america1 then the affinities of the ,megathere with the ,sloths would undoubtedly have been viewed from a truer point than at the time when1--the ,scelidothere1 and analogous transitional forms1 being unknown1--it was regarded as a gigantic ,sloth4 ,having indicated the principal characters of the cranium of the ,scelidothere1 which determine its affinities amongst the ,edentata1 there next remains to be considered the relative position1 extent1 and connections1 of the different bones composing the cranium4 ,the occipital bone constitutes the whole of the posterior1 the usual proportion of the inferior1 and a small part of the upper and lateral portions of the cranial cavity3 there is a small descending ex-occipital process immediately exterior to the condyle3 above this part the occipital bone is articulated to the mastoid process of the temporal1 and the supra-occipital plate is joined by a complex dentated lambdoidal suture to the two parietals1 without the intervention of interparietal or ,wormian bones2 the course and form of the lambdoidal suture is shown in ,pl4 ,,xxii42 it has the same relative position as in the ,orycterope2 in the ,armadillos1 the suture runs along the angle between the posterior and superior surfaces of the skull4 ,the thickness of the occipital bone1 at this angle1 in the ,scelidothere1 exceeds an inch1 and its texture consists of a close massive diplo1 between the dense outer and inner tables1 7,pl4 ,,xxiii4 fig4 #a47 ,the squamous portion of the temporal bone has a very slight elevation1 not extending upon the side of the cranium more than half an inch above the zygoma2 it is thus relatively lower than in the ,orycteropus2 but is similarly bounded above by an almost straight line1 7,pl4 ,,xxi41 fig4 #a474 ,the mastoid process is small1 compressed1 with a rounded contour2 immediately internal to it is a very deep depression1 corresponding to that for the digastric muscle4 ,but the most interesting features in this region of the temporal bone consist in the free condition of the tympanic bones1 and the presence of a semicircular pit1 immediately behind the tympanic bone for the articulation of the styloid element of the hyoid or tongue-bone3 in these points we trace a most remarkable correspondence with the ,glossothere1 and in the separate tympanic bone the same affinity to the ,orycteropus1 as has been already noticed in the more bulky extinct ,edental4 ,this correspondence naturally leads to a speculation as to the probable generic relationship between the ,glossothere and ,scelidothere3 now it may first be remarked that the styloid articular depression is relatively much larger and much deeper in the ,glossothere than in the ,scelidothere2 in the former its diameter equals1 as we have seen1 one inch2 in the ,scelidothere it measures only a third of an inch1 the whole cranium being about two-fifths smaller2 if we turn next to the anterior condyloid foramina1 which in the ,scelidothere are double on each side1 we obtain from them evidence that the muscular nerve of the tongue could only have been one-third the size of that of the ,glossothere4 ,these proofs of the superior relative development of the tongue in the ,glossothere indicate a difference of habits1 and a modification1 probably1 of the structure of the locomotive extremities2 and when we associate these deviations from the ,scelidothere1 with the known difference in the position of the occipital plane1 which in the ,glossothere corresponds with that in the ,myrmecophaga and ,bradypus1 we shall be justified in continuing to regard them1 until evidence to the contrary be obtained1 as belonging to distinct genera4 ,the parietal bones present an oblong regular quadrate figure1 the sagittal suture running parallel with the squamous1 and the frontal with the lambdoidal suture2 there is scarcely any trace of denticulations in the sagittal suture2 the bones are of remarkable thickness1 varying1 at this suture1 from six to nine lines1 and their opposed surfaces are locked together by narrow ridges1 which slightly radiate from the lower to the upper part of the uniting surface3 the substance of the bone consists of an uniform and pretty dense diplo2 and there are no sinuses developed in it4 ,we can hardly regard the extraordinary air-cells which occupy the interspace of the two tables of the skull in the parietal and occipital bones of the ,glossothere 7,pl4 ,,xvi41 fig4 #c7 as a difference depending merely on age4 ,the frontal and thmoid bones are broken away in the present cranium4 ,the sphenoid commences two inches in front of the foramen occipitale2 the fractured state of the skull does not allow its anterior or lateral limits to be accurately defined2 its body is occupied with large air-sinuses2 the only part1 indeed1 of this bone which is exposed to observation is that which forms part of the floor of the cranium2 and this we shall now proceed to describe1 in connexion with the other peculiarities of the cranial cavity1 7fig4 #a4 ,pl4 ,,xxiii47 ,the body of the sphenoid is impressed on its cranial surface with a broad and shallow sella turcica 7a71 bounded by two grooves1 7b b17 leading forwards and inwards from the carotid foramina 7c72 the line of suture between the sphenoid and occipital bones runs along a slight transverse elevation 7d71 which bounds the sella posteriorly2 this suture is partially obliterated3 a slight median protuberance 7e7 bounds the sella turcica anteriorly2 there are neither anterior nor posterior clinoid processes4 ,external to the carotid channel there is a wide groove 7f7 leading to the foramen ovale 7g72 this foramen is about one-third smaller than in the ,glossothere1 and therefore1 as compared with the anterior condyloid foramina1 indicates that the tongue was endowed with a greater proportion of sensitive than motive power in the ,scelidothere3 but in reasoning on the size of this nerve1 it must be remembered that in both animals certain branches1 both of the second and third divisions of the fifth pair of nerves1 are to be associated with the persistence of large dental pulps1 of which they regulate the secreting power4 ,anterior to the foramen ovale1 and at the termination of the same large common groove1 lodging the trunk of the fifth pair of nerves is the foramen rotundum 7h72 this leads to a very long canal1 the diameter of which is five lines1 being somewhat less than that for the third division of the fifth pair4 ,the anterior sphenoid is broken away1 so that no observation can be made on the optic foramina4 ,the basilar process of the occipital bone is perforated at its middle by two small foramina 7i7 on the same transverse line1 about half an inch apart4 ,in the ,armadillo these foramina do not exist3 in the ,orycterope they are present1 but open beneath an overhanging ridge1 which is continued from them to the upper part of the anterior condyloid foramen on each side4 ,the sella turcica of the ,orycterope is deeper and narrower than in the ,scelidothere2 and is separated from the basilar occipital process by a transverse ridge1 which sends forward two short clinoid processes2 two smaller anterior clinoid processes project backwards from the angle of the anterior boundary of the sella turcica4 ,the foramina ovalia and rotunda open in the same continuous groove1 as in the ,glossothere and ,scelidothere1 but they are relatively wider apart2 and the canal for the third division of the fifth pair is shorter1 and runs more directly outwards4 ,the petrous bone in the ,scelidothere is relatively larger than in the ,glossothere1 but this probably arises from the precocious development of the organ of hearing in the present immature specimen in obedience to the general law4 ,the trunk of the fifth pair of nerves does not impress it with so deep and well defined a groove as in the ,glossothere2 the elliptic internal auditory foramen 7k7 is situated about the middle of the posterior surface2 behind this is the aqueductus vestibuli2 and immediately posterior to the petrous bone is the foramen jugulare 7l73 the shape of the os petrosum agrees more with that of the ,armadillo than with that of the ,orycterope4 ,an accidental fracture of the right os petrosum demonstrates its usual dense and brittle texture1 and at the same time has exposed the cochlea with part of its delicate and beautiful lamina spiralis4 ,the conservation of parts of the organs of vision in certain fossils1 has given rise to arguments which prove that the laws of light were the same at remote epochs of the earth's history as now2 and the structures ,i have just mentioned1 in like manner1 demonstrate that the laws of acoustics have not changed1 and that the extinct giants of a former race of quadrupeds were endowed with the same exquisite mechanism for appreciating the vibrations of sound as their existing congeners enjoy at the present day4 ,the brain1 being regulated in its development by laws analogous to those which govern the early perfection of the organ of hearing1 appears to have been relatively larger in the ,scelidothere than in the ,glossothere3 it was certainly relatively longer2 the fractured cranium gives us six inches of the antero-posterior diameter of the brain1 but the analogy of the ,orycterope would lead to the inference that it extended further into the part which is broken away4 ,the greatest transverse diameter of the cranial cavity is four inches eight lines3 these dimensions1 however1 are sufficient to show that the brain was of very small relative size in the ,scelidothere2 and1 both in this respect1 and in the relative position of its principal masses1 the brain of the extinct ,edental closely accords with the general character of this organ in the existing species of the same ,order4 ,we perceive by the obtuse ridge continued obliquely upwards from above the upper edge of the petrous bone1 that the cerebellum has been situated wholly behind the cerebrum1 we learn also from the same structure of the enduring parts that these perishable masses were not divided1 as in the ,manis1 by a bony septum1 but by a membranous tentorium1 as in the ,glossothere and ,armadillos3 in the ,orycteropus1 as has been before remarked1 there is a strong1 sharp1 bony ridge extending into each side of the tentorium4 ,the vertical diameter of the cerebellum and medulla oblongata equals that of the cerebrum1 and is two inches three lines3 the transverse diameter of the cerebellum was about three inches nine lines2 its antero-posterior extent about one inch and a half4 ,the sculpturing of the internal surface of the cranial cavity bespeaks the high vascularity of the soft parts which it contained1 and there are evident indications that the upper and lateral surfaces of the brain had been disposed in a few simple parallel longitudinal convolutions4 ,the two anterior condyloid foramina 7m7 have the same relative position as the single corresponding foramen in the ,glossothere1 ,orycterope1 and ,armadillos1 and the inner surface of the skull slopes outwards from these foramina to the inner margin of the occipital condyle4 ,of the bones of the face there remain only portions of the malar1 lachrymal1 palatine1 and maxillaries4 ,the chief peculiarities of the malar bone have been already noticed3 the breadth of the base of the descending masseteric processes is two inches two lines2 its termination is broken off3 the length of the ascending post-orbital process of the malar cannot be determined from the same cause1 but it is fortunate that sufficient of this part of the cranium should have been preserved to give this evidence of the affinities of the ,scelidothere to the ,megathere4 ,the malar bone is continued anteriorly1 in a regular curve forwards and upwards1 to the lachrymal bone1 and completes1 with it1 the anterior boundary of the orbit3 the size of the orbit is relatively smaller than in the ,orycterope1 and still less than in the ,ant-eaters3 here1 however1 we have merely an exemplification of the general law which regulates the relative size of the eye to the body in the mammalia4 ,the malar bone does not extend so far forwards in front of the orbit as in either the ,orycterope or ,armadillo2 in the inclination1 however1 with which the sides of the face converge forwards from the orbits1 the ,scelidothere holds an intermediate place between the ,armadillos and ,orycterope4 ,the lachrymal bone does not extend so far upon the face in the ,scelidothere as in the ,orycterope2 in which respect the ,scelidothere resembles more the ,megathere4 ,the foramen for the exit of the infra-orbital nerve has the same situation near the orbit as in the ,megathere2 its absolute distance from the anterior border of the orbit is only half that in the ,orycterope4 ,the foramen is single in the ,scelidothere1 as in the ,orycterope2 in the ,megathere there are two or three ant-orbital foramina4 ,the vertical diameter of this foramen is eight lines1 the transverse diameter four lines4 ,so much of the outer surface of the superior maxillary bones as has been preserved1 is smooth and vertical4 ,each superior maxillary bone contains the sockets of five teeth1 occupying an antero-posterior extent of three inches seven lines1 7,pl4 ,,xxii4 and ,,xxiii4 fig4 #c74 ,the posterior alveolus is situated just behind the transverse line1 extending across the anterior boundary of the orbits2 the remaining sockets of the molar series extend forwards three inches in front of the orbits4 ,in the ,megatherium1 the roots of the five superior molars are all situated behind the anterior boundary of the orbit3 in the ,orycteropus1 on the contrary1 the grinders are all placed in advance of the orbit2 so that the ,scelidothere resembles that species more than the ,megathere in the relative location of the teeth4 ,the palatal interspace between the roots of the last molar tooth of each series is eleven lines2 the palate gradually though slightly widens1 as it advances forwards3 the posterior margin of the palate is terminated by an acute-angled notch4 ,in the breadth of the bony palate the ,scelidothere is intermediate between the ,megathere and ,orycterope4 ,the anterior of the upper molars is represented at fig4 #c1 #d1 and #e1 ,pl4 ,,xxi41 and at #a1 fig4 #c1 ,pl4 ,,xxiii42 it corresponds closely in form and size with the opposite molar below2 the base of the triangle given by its transverse section is turned inwards and obliquely forwards4 ,the second molar of the upper jaw1 also presents in transverse section a triangular form1 with the angles rounded off2 but the inner side of the tooth is traversed by a longitudinal groove4 ,the largest diameter of the transverse section1 which is placed obliquely as regards the axis of the skull1 measures ten lines and a half2 the opposite diameter of the tooth is six lines4 ,the third and fourth molars present the same form and size1 and relative position as the second4 ,the fifth molar is the smallest of the series2 its transverse section gives an inequilateral triangle1 with the corners rounded off2 the broadest side is turned outwards1 and is slightly concave2 the antero-posterior diameter of this tooth is seven lines2 the transverse four lines4 ,the length of the teeth in the upper jaw is about two inches and a half4 ,it is almost superfluous to observe that the teeth of the ,scelidothere1 as in other ,bruta1 are without fangs1 and have their inserted base excavated by large conical cavities1 for the lodgment of a persistent pulp4 ,the tooth is composed of a small central body of coarse ivory or #8dentine1' traversed by medullary canals1 which at the periphery of the coarse dentine anastomose by loops1 from the convexity of which the calcigerous tubes are given off which form the fine dentine3 the layer of this substance1 which immediately surrounds the coarse dentine1 is about one line and a half in thickness1 and the whole is invested with a very thin coating of cement4 ,the teeth of the ,scelidothere thus present a more resisting structure than do those of the ,mylodon2 having a larger proportion of the dense ivory composed of the minute calcigerous tubes1 and a much smaller proportion of the softer external cmentum2 in this respect the ,scelidothere recedes farther from ,megathere1 and approaches nearer the ,armadillos than does the ,mylodon4 ,the lower jaw resembles1 in the general form of the posterior moiety which is here preserved1 that of the ,sloth and ,mylodon more than that of any other ,edentate species4 ,its deep posterior angle is produced backwards1 and a broad coronoid process rises and nearly fills the zygomatic space2 the condyle is flat1 as the glenoid surface has already indicated2 its transverse diameter is an inch and eight lines2 its antero-posterior diameter seven lines3 it is principally extended inwards beyond the vertical line of the ascending ramus4 ,the lower contour of the jaw describes an undulating line2 which1 commencing from the posterior angle1 is at first gently convex1 then slightly concave1 then again convex1 below the alveoli of the teeth1 where it is rounded and expanded1 as in the ,orycterope4 ,the fractured condition of the right ramus of this part fortunately exposed the roots of the four grinding teeth1 which constitute the dental series on each side of the lower jaw4 ,the length of the jaw occupied by these four alveoli is three inches ten lines1 which exceeds a little that of the opposed five grinders above2 the ramus of the jaw gradually diminishes in all its dimensions anterior to the molar teeth2 the dental canal passes in a gentle curve below1 and on the inner side of the alveoli1 whence it gradually inclines to the outer wall of the jaw4 ,the whole ascending ramus of the jaw consists of a very thin plate of bone2 it is slightly concave on the inner side1 and the inferior margin of the produced angle inclines inwards1 as in the ,mylodon and ,sloth2 it is impressed on the outer side with two shallow depressions1 and two parallel ridges1 both following the gentle curvature of the part4 ,there is a foramen on the outer side of the ramus at the anterior part of the base of the coronoid process corresponding with that in the lower jaw of the ,mylodon1 but the longitudinal channel which runs along the outer side of the alveolar processes is wanting1 and the expansion at the base of those processes is more sudden and relatively greater2 the general correspondence1 however1 between these lower jaws is such as would lead to the idea that they belonged to animals of the same genus1 were it not that the teeth present modifications of form in the ,scelidothere1 as distinct from those of the ,mylodon1 as are any of the minor dental differences on which genera or subgenera of existing ,mammalia are founded in the present state of ,zoological ,classification4 ,to make this distinction more readily intelligible1 ,i have given a view of the transverse section of the teeth in the right ramus of the lower jaw 7fig4 #d1 ,pl4 ,,xxiii471 corresponding with that of the ,mylodon ,darwinii1 7,pl4 ,,xvii41 fig4 #e74 ,in the present subgenus the antero-posterior extent of the four alveoli of the lower jaw nearly equals four inches1 and is relatively greater than in the ,mylodon1 although the teeth are placed closer together2 this is owing to their greater relative size4 ,the first molar tooth presents the simplest form2 its transverse section is a compressed inequilateral triangle with the angles rounded off2 the longest diameter of this section which is parallel with the inner alveolar border is eleven lines1 the transverse diameter almost six lines2 the base or broadest side of the triangle is turned inwards1 and is slightly concave2 the two smaller sides are also slightly concave4 ,the second molar is placed more obliquely in the jaw2 the long axis of its transverse section intersects at an acute angle that of the jaw itself2 the transverse section presents a compressed or oblong form1 with the larger end next the outer side1 and the smaller end next the inner side of the jaw2 this end is simply rounded1 but the outer end presents a sinuosity1 corresponding to a broad groove which traverses the whole length of the outer side of the tooth2 the anterior1 which corresponds to the internal side or base of the transverse section of the preceding molar1 is slightly concave4 ,the third molar has nearly the same form and relative position as the preceding2 the long diameter of the transverse section is1 in both1 ten lines and a half2 the principal transverse diameter is1 in the second molar five lines1 in the third nearly six2 the difference of form observable in these as compared with the two middle grinders of the ,mylodon is well-marked2 in the latter these teeth are impressed with a longitudinal groove on their inner sides2 in the ,scelidothere they have a similar impression along their outer but not along the inner side4 ,in the last molar the resemblance is much closer1 and the modification of form by which it differs from the preceding ones is of the same kind2 the transverse section gives an irregular oblong figure with its axis nearly parallel with that of the jaw1 and constricted at the middle by sinuosities produced by two wide channels which traverse longitudinally1 one the outer1 the other the inner side of the tooth2 the latter groove is much wider and shallower in the ,scelidothere than in the ,mylodon4 ,the two lobes produced by these grooves are more equal in ,scelidothere2 the anterior one is concave on its anterior surface instead of convex as in the ,mylodon2 the posterior one is more compressed2 the longitudinal or antero-posterior diameter of the transverse section of this tooth is one inch five lines2 the greatest transverse diameter is nine lines2 the diameter of the isthmus joining the lobes is three lines and a half2 the entire length of this tooth is three inches three lines4#df ,,vertebral ,,column4 ,of this part of the skeleton of the ,scelidothere1 ,mr4 ,darwin's specimen includes1 as is represented in ,plate ,,xx41 the cervical1 part of the dorsal1 and the sacral series of vertebr in a more or less perfect condition4 ,the cervical vertebr present the ordinary mammalian number1 seven1 and are free1 or so articulated as to have permitted reciprocal movement upon each other4 ,their transverse processes are perforated as usual for the vertebral arteries4 ,these processes in the atlas are remarkable for their great breadth1 length1 and thickness2 and indicate the muscular forces which must have worked the head upon the spine to have been very powerful4 ,the axis is provided with a robust #8processus dentatus1' having a base equal in breadth to the body of the axis itself2 and a smooth articular convexity on the side of the apex on which the ring of the atlas rotated4 ,the line of union between the axis and its characteristic process1 which here resembles the body of an abortive vertebra1 is very distinct4 ,the transverse processes of the vertebra dentata are comparatively feeble1 but this condition is amply compensated for by the great development of the spinous process4 7,pl4 ,,xxiv4 fig4 #a47 ,this process is bent backwards at nearly a right angle1 overlaps with its reflected extremity the spine of the third cervical vertebra1 and rests by its base1 on the under part of which are the posterior articular surfaces1 upon the broad and strong anterior oblique processes of the third vertebra4 ,the third1 fourth1 fifth1 and sixth cervical vertebr have moderately developed and pointed spinous processes3 their transverse processes are broad1 and extend obliquely backwards1 and slightly overlap each other4 ,on the under part of the transverse process of the sixth cervical vertebra there is the fractured base of what ,i conjecture to have been an expanded aliform plate1 analogous to that observable in the corresponding vertebra of the ,orycterope4 ,the seventh cervical vertebra has part of the articular depression for the head of the first rib upon each side of its body3 the transverse process is feebly developed1 but the spine is double the height and size of those of the preceding vertebr4 ,the spinous process of the first dorsal vertebra in like manner rises to twice the height of the preceding spine of the seventh cervical1 and preserves an equal antero-posterior diameter from its base to its summit1 which is thick and slightly bent backwards3 four or five succeeding dorsal vertebr give evidence of having been surmounted by spines of equal height and strength4 ,the transverse processes of these dorsal vertebr present bold concavities on their inferior part for the reception of the tubercles of the ribs1 and they gradually ascend upon the base of the spines as the vertebr are placed further back1 so as to increase the expansiveness of the chest4 ,the state of the fossil did not afford further information as to the condition of this part of the vertebral column1 but the parts which have been preserved are precisely those from which the most interesting inferences as to the affinities and habits of the extinct quadruped can be deduced4 ,whether the ,megatherium be most nearly allied to the tribes of the ,sloth or ,armadillo has been a question under recent discussion1 and1 as a corollary of this problem1 whether its habits were those of a scansorial or of a fossorial quadruped4 ,for1 strange as it may appear at first sight1 there have not been wanting arguments1 and those urged by an anatomist to whom we owe much novel and interesting information respecting the extinct ,edentata1 in support of the belief that the ,megatherium1 gigantic and ponderous as must have been its frame1 actually climbed trees like a ,sloth1 and had claws and feet organised for prehensile actions1 and not in accordance with that type by which they are usually adapted for digging up the soil4#dg ,now1 in whatever degree the ,megatherium may be involved in this question1 the smaller ,megatherioid species at present under consideration must be at least equally implicated in it4 ,in the adaptation of the frame of a mammiferous quadruped for especial and peculiar actions and modes of life1 such as for climbing and living in trees1 or for burrowing and seeking concealment in the earth1 not only the immediate instruments1 as the feet1 are modified1 but the whole of the osseous and muscular fabric is more or less impressed with corresponding adaptations1 whilst at the same time these special adjustments are invariably subordinated to the type of organization which characterizes the group4 ,the type of the order ,bruta or ,edentata is well-marked2 one or more claws of unusual length and strength1 characterize the fore-feet and sometimes the hind-feet in every genus1 and the term #8,macronykia' would more aptly designate them than the term which ,cuvier substituted for the good old ,linnean appellation4 ,the uniform absence of true roots to the teeth1 where these are present1 is another general character2 the skeleton exhibits many well-marked peculiarities common to the whole order2 while at the same time it is modified in various modes and degrees in accordance with the peculiar habits and exigencies of the species4 ,one of the regions of the skeleton which manifests adaptive modifications of this kind in the most remarkable degree is the cervical division of the vertebral column4 ,in one edentate species it is lengthened out by two additional vertebr more than in any other mammal2 in another it is reduced by anchylosis to as great an extent below the regular number of moveable pieces3 and these1 the two most opposite conditions of the cervical vertebr which are to be met with in the mammiferous class are related to equally diverse and opposite habits of life4 ,with respect to the ,ai1 or three-toed ,sloth1 8an animal1 great part of whose life1 when not engaged in eating1 is spent in sleeping on trees1--an easy attitude for repose is most essential to its comfortable existence2 and accordingly we find1 that the auxiliary vertebr at the base of the neck contribute to produce that flexibility of this organ which allows the head of the animal to incline forwards and rest upon its bosom40 ,dr4 ,buckland1 from whose ,paper on the 8,adaptation of the ,structure of the ,sloths to their peculiar ,mode of ,life10#dh the preceding judicious physiological remark is quoted1 adduces the authority of ,mr4 ,burchell in proof that the ,sloth can in a remarkable manner and with great facility twist its head quite round1 and look in the face of a person standing directly behind it1 while at the same time the body and limbs remain unmoved4 ,a single glance at the length and slenderness of the cervical region of the spine1 and of the feeble condition of the transverse and spinous processes in the vertebr composing that part of the skeleton of the ,sloth1 is enough to show its adaptation to increase the rotatory motion and flexibility of the neck4 ,in describing the skeleton of a species of ,armadillo 7,dasypus #f-;cinctus1 ,linn47#di ,i was led in like manner to point out the subserviency of the peculiarities of the cervical vertebr to the habits and mode of life of that animal2 observing that the 8anchylosis of the cervical vertebr obtains in the ,cetacea1 as well as in the genus ,dasypus1 and that as in the aquatic order this firm connexion of the cervical vertebr assists materially in enabling the head to overcome the resistance of the dense fluid through which they perpetually move1 so in the ,armadillos a like advantage may be derived from this structure during the act of displacing the denser material in which they excavate their retreats40#ej ,having in view these well-marked examples of the subserviency of the structure of the bones of the neck to the habits of existing species of the order ,bruta1 ,i proceeded to investigate the structure of the corresponding part of the skeleton in the ,scelidotherium1 hoping thereby to gain a new and useful element in the determination of the problem at present under discussion1 as to the affinities and habits of the extinct ,megatherioid quadrupeds4 ,the fossil1 in its original state1 yielded a view of so much of the anterior part of the bodies of the cervical vertebr as proved that they were neither so numerous as in the ,sloth1 nor anchylosed together as in the ,armadillos3 after a long and careful chiselling at the hard matrix in which they were imbedded1 the transverse and spinous processes were exposed to view1 as they are represented in ,plates ,,xx4 and ,,xxiv4 ,the description of these processes has already been given4 ,on comparing the cervical vertebr of the ,scelidotherium with those of the existing ,bruta1 the closest resemblance to them was found in the skeleton of the ,orycterope4 ,now this quadruped1 though not so rapid a burrower1 or so strictly a subterranean species as the ,armadillos1 participates1 nevertheless1 to a certain extent1 in their fossorial habits1 and is closely allied to them in general structure3 it differs from them1 indeed1 mainly in a modification of the dental system1 in the absence of dermal armour1 and of anchylosis of the cervical vertebr4 ,but the advantages which1 as a burrower1 it would have derived from the latter structure1 are compensated for by the shortness of the cervical vertebr1 and by the great development and imbricated or interlocking co-adaptation of the transverse and anterior spinous processes of the cervical vertebr4 ,the analogous quadruped in the ,south ,american ,continent--the great ant-eater 7myrmecophaga jubata7 which uses its powerful compressed fossorial claws for breaking through the hard walls of the habitations of its insect prey1 but which does not excavate a subterraneous retreat for itself1 presents the cervical vertebr of a more elongated form1 and without that development of the spinous and transverse processes which tend to fix the neck and increase the size of the muscles which move the head3 and1 if we could conceive that its fore-feet were employed to scratch up vegetable roots1 instead of disinterring termites1 there would be no reason to expect any modification of the cervical vertebr as a direct consequence of such a difference in the application of its fossorial extremities3 when1 therefore1 we find that the cervical vertebr do actually differ in two myrmecophagous species1 to the extent observable in the ,cape and ,south ,american ant-eaters1 we arrive legitimately at the conclusion that such difference relates to fossorial habits of the one species1 in which habits the other does not participate4 ,now1 therefore1 if this conclusion be just in regard to the ,orycterope1 it must bear with more force upon the question of the habits of the ,scelidotherium as the mechanism for strengthening the connection of cervical vertebr1 and for augmenting the surface of attachment of the muscles which worked the head and neck1 is more strongly wrought out in that extinct species4 ,the great size and strength of the spinous process of the dentata1 and the mode in which it is interlocked with the spinous and oblique processes of the third cervical1 together with the imbricated disposition of the transverse processes of this and the succeeding vertebr1 and the remarkable height of the dorsal spines1 all combine to indicate in a very striking manner1 if not to demonstrate1 that the conical head of the present species1 which is comparatively small and slender1 and for its own mere support requiring therefore no such mechanism1 was used in aid of the fossorial actions of the extremities4 ,as the cervical vertebr of the ,megatherium have their processes comparatively weaker than in the ,scelidotherium1 and the anterior dorsal spines are relatively shorter1 it may be concluded1 that whatever were the extent or nature of the fossorial labours of the enormous claws with which it was provided1 the head did not co-operate with the digging implements in their especial task in the same degree as in the ,scelidothere and ,orycterope4 ,at the same time there is no modification of the cervical region of the spine of the ,megathere corresponding with those which we have seen to be subservient to the arboreal habits of the sloth1 a remark which will not be deemed superfluous by those who have perused the acute observations and arguments adduced by ,m4 ,lund in favour of the scansorial character of the extremities of the ,megatherium and ,megalonyx4 ,the fragments of the dorsal vertebr and ribs of the ,scelidotherium1 which are figured in ,plate ,,xx41 offer no modifications which need detain our attention2 they closely conform1 excepting in the greater relative height of the anterior dorsal spines1 already noticed1 with the ,megatherioid type4 ,the sacrum manifests in its vast expanse1 the great development of the posterior transverse processes to join the ischium1 the capacious medullary cavity1 and wide nervous foramina1 a like conformity with the ,megatherium1 and a corresponding harmony with the disproportionate bulk of the hind legs4 ,,bones ,,of ,,the ,,extremities4 ,the ,scapula in its double spine1 the osseous arch formed by the confluence of the acromion with the coracoid process1 and the substitution of a distinct foramen for the suprascapular notch1 agrees with that of the ,megatherium3 but the span of the acromial arch is relatively wider1 and the surface for the articulation of the clavicle is better marked4 ,this articular surface1 which is distinctly shewn upon the acromion of both the scapul in ,pl4 ,,xx4 is the more interesting1 as being the only evidence of the clavicle of the ,scelidothere which we at present possess2 but it is enough to prove that this quadruped enjoyed all the advantages in the actions of the fore extremity1 which arise out of the additional fixation of the shoulder-joint afforded by the clavicle--a bone which the extinct ,megatherioids are the largest of the mammiferous class to possess in a completely developed state4 ,the form1 position1 and aspect of the glenoid cavity for the humerus closely correspond with the condition of the same part in the ,megatherium4 ,the limits of the acromial and coronoid portions of the arch were still defineable in the present skeleton1 which indicates the nonage of the individual in the unanchylosed condition of most of the epiphysiaes4 ,in regard to the presence of a clavicle in the ,megalonyx ,m4 ,lund has deduced certain conclusions1 which1 if well founded1 would be equally applicable to the present allied species1 and to the great ,megatherium4 ,i am induced1 therefore1 to offer a few physiological observations on that bone1 which appear to me to lead to a more correct interpretation of its uses and relations in the great mammiferous animals now under consideration4 ,when the anterior extremities in mammalia are used simply for the purpose of progressive motion on dry land1 as in the ,pachyderms and ,ruminants1 or in water1 as in the ,cetaceans1 there is no clavicle2 this bone is introduced between the sternum and acromion1 in order to give firmness and fixity to the shoulder-joint when the fore-leg is to discharge some other office than that of locomotion4 ,in these cases1 however1 the clavicle exists in various degrees of development1 and even its rudiment may be dispensed with in some of the actions which require a considerable extent of lateral or outward motion1 and of freedom of rotation of the fore-limb4 ,when1 therefore1 we find the clavicle fully developed in the skeleton of an extinct mammiferous animal1 and so placed as to give the humeral articulation all the benefit of this additional mechanism1 we may confidently expect that it will afford an insight into the habits and mode of life of such extinct species4 ,m4 ,lund#ea has argued from the clavicle of the ,megalonyx1 that it climbed like a ,sloth4 8,animals10 says ,sir ,c4 ,bell1#eb 8which fly or dig1 or climb1 as ,bats1 ,moles1 ,porcupines1 ,squirrels1 ,ant-eaters1 ,armadillos1 and ,sloths1 have this bone2 for in them1 a lateral or outward motion is required40 ,but in regard to the present problem1 we have to enquire whether the clavicle manifests any modifications of form1 of strength1 or development in relation to the special differences of these several actions1 with which its presence is asserted to be associated8 ,in mammals which fly1 the clavicle is always complete3 the rabbit1 the fox1 and the badger are instances of burrowing animals in which the clavicle is absent or rudimental4 ,the presence of a perfect clavicle is not more constant in climbing quadrupeds4 ,the ,ai1 for example1 has an incomplete clavicle1 which is attached to the acromion process1 and terminates in a point about one-fourth of the distance between the acromion and the top of the sternum1 to which the clavicular style is attached by a long slender ligament3 the advantage1 therefore1 which a perfect clavicle affords in the fixation of the shoulder-joint1 is lost to this climber par excellence4 ,again1 the ,bears1 which are the bulkiest quadrupeds that are gifted with the faculty of climbing1 and this in so perfect a degree that the ,sun-bears of the ,eastern ,tropics may be termed arboreal animals1--these scansorial quadrupeds are destitute of even the smallest rudiment of a clavicle1 as ,i have ascertained by repeated careful dissection4 ,since1 therefore1 a clavicle in any degree of development is not essential to a climbing quadruped1 we must seek for some other relation and use of that remarkably strong1 and perfect bone1 as it exists in the ,megathere1 ,megalonyx1 and ,scelidothere4 ,the absence of #8dentes primores' or of anterior or incisive teeth in these quadrupeds at once sets aside any idea of its connection with an action of the fore extremities1 very common in the mammals which possess clavicles1 viz41 that of carrying the food to the mouth1 and holding it there to be gnawed by the teeth4 ,flying is of course out of the question1 although our surprise would hardly be less at seeing a beast as bulky as an elephant climbing a tree1 than it would be to witness it moving through the air4 ,if now we restrict our comparison to the relations of the clavicle in that order of ,mammalia to which the extinct species in question belonged1 we shall see that it is most constant1 strongest1 and most complete in those species which make most use of their strong and long claws in displacing the earth1 as the ,armadillos and ,orycteropus3 and1 as the clavicle is incomplete in one climbing ,edental1 we are naturally led to conclude that its perfect development in an extinct species must have been associated with uses and relations analogous to those with which it coexists in other genera of the same order4 ,thus it will be seen1 that1 in rejecting the conclusion drawn by ,m4 ,lund from the presence of a clavicle1 ,i concur in the opinion expressed by ,dr4 ,buckland#ec that the ,megatherium--and with it the ,megalonyx and ,scelidotherium--had the shoulder-joint strengthened by the clavicle1 in reference to the office of the fore-arm1 as an instrument to be employed in digging roots out of the ground4 ,not1 however1 that these gigantic quadrupeds fed on roots1 but rather1 as the structure of the teeth would show1 on the foliage of the trees uprooted by the agency of this powerful mechanism of the fore-legs1 and of the otherwise unintelligible colossal strength of the haunches1 hind legs1 and tail4 ,the humerus presents a large convex oval head1 on each side of which is a tuberosity for the implantation of the supra- and sub-scapular muscles3 these tuberosities do not rise above the articular convexity1 so as to restrict the movements of the shoulder-joint1 as in the ,horse and ,ruminants1 but exhibit a structure and disposition conformable to those which characterize the proximal extremity of the humerus in other mammalia which enjoy rotatory movements of the upper or fore-limb4 ,the tuberosities are1 however1 relatively more developed1 and give greater breadth to the proximal end of the humerus in the ,scelidothere than in the ,megathere4 ,the distal end of the humerus1 although mutilated1 clearly indicates that it had the same characteristic breadth of the external and internal condyles1 as in the ,megatherium4 ,in fig4 #a4 ,pl4 ,,xxv4 which gives a front view of the left humerus1 the broad internal condyle1 with its extremity broken off1 is seen projecting to the left hand2 both in this figure and in fig4 #b4 in which the internal side of the humerus is turned towards the observer1 the wide groove1 with its two osseous boundaries1 is shewn1 which plainly indicates that the left condyle was perforated for the direct passage of the artery or median nerve1 or of both1 to the fore-arm4 ,the groove for the musculo-spiral nerve on the outer side of the humerus is over-arched at its upper part by a strong obtuse process2 which is comparatively less developed in the ,megatherium4 ,the trochlear or inferior articular surface of the humerus presents1 as in the ,megatherium1 two well-marked convexities1 with an intervening concavity3 this indication of the rotatory power of the fore-leg is confirmed by the form of the head of the radius4 ,in ,pl4 ,,xxv4 fig4 #d4 a view is given of this articular surface3 it presents the form of a subcircular gentle concavity1 which plays upon the outer convexity of the humeral articular surface3 immediately below the upper concavity the radius presents a lateral smooth convex surface1 which rotates upon a small concavity on the ulna1 analogous to the #8lesser semilunar1' in human anatomy1 in which the mechanism for rotation1 so far as the upper joint of the radius is concerned1 is not more elaborately wrought out than in the present extinct edentate quadruped4 ,the radius expands as it proceeds to the elbow-joint1 where it attains a breadth indicative of the great power and size of the unguiculate paw1 of which it may be called the stem1 and to the movements of which it served as the pivot4 ,all the bones of the fore-limb just described--the scapula1 the humerus1 and the radius1--indicate by the bold features and projections of the muscular ridges and tubercles the prodigious force which was concentrated upon the actions of the fore-paw1 and the ulna1 in its broad and high olecranon 7of which a side view is given in fig4 #b4 ,pl4 ,,xxv47 gives corresponding evidence4 ,the great semilunar concavity is traversed by a sub-median smooth ridge1 which plays upon the interspace of the two humeral convexities4 ,the body of the bone is subcompressed1 straight1 and diminishes in size as it approaches the carpal joint3 the immediate articulating surfaces are wanting in both the radius and ulna1 the epiphyseal distal extremities having become detached from their respective diaphyses4 ,of the terminal segment of the locomotive extremities1 the only evidence among the remains of the skeleton of the ,scelidothere is the ungueal phalanx figured at ,pl4 ,,xxvii4 #c1 #d1 and #e2 but as it is uncertain whether it belongs to the fore or hind-foot1 it will be described after the other bones of the extremities have been noticed4 ,of these bones the femur is the most remarkable1 both for its great proportional size1 and its extreme breadth1 as compared with its length or thickness3 but in all these circumstances the affinity of the ,scelidothere with the ,megathere is prominently brought into view4 ,there is no other known quadruped with which the ,scelidothere so closely corresponds in this respect4 ,in proceeding1 however1 to compare together the thigh-bones of these two extinct quadrupeds1 several differences present themselves1 which are worthy of notice3 of these the first is the presence in the ,scelidothere of a depression for a #8ligamentum teres' on the back part of the head of the femur1 near its junction with the neck of the bone3 this is shewn in the posterior view of the femur given in ,pl4 ,,xx4 ,the head itself forms a pretty regular hemisphere3 the great trochanter does not rise so high as in the ,megatherium1 but1 relatively1 it emulates it in breadth3 the small trochanter is proportionally more developed3 the external contour of the shaft of the femur is straighter in the ,scelidothere than in the ,megathere1 and the shaft itself is less bowed forwards at that part4 ,the articular condyles occupy a relatively smaller space upon the distal extremity of the femur in the ,scelidothere1 and they differ more strikingly from those of the ,megathere1 in being continued one into the other3 the rotular surface1 for example1 which is shewn in fig4 #e4 ,pl4 ,,xxv4 is formed by both condyles1 while in the ,megatherium it is a continuation exclusively of the external articular surface4 ,the patella1 which works upon the above-mentioned surface1 is a thick strong ovate bone1 with the smaller end downwards3 rough and convex externally1 smooth on the internal surface1 which is concave in the vertical and convex in the transverse directions4 ,of the bones of the leg only the proximal end of the tibia is preserved2 but this is valuable1 as shewing another well-marked difference between the ,scelidothere and ,megathere2 for whereas in the latter the fibula is anchylosed with the tibia1 this bone1 in the ,scelidothere1 presents a smooth flat oval articular surface1 which is shewn in fig4 #b4 ,pl4 ,,xxvii4 below the outer part of the head of the bone2 from the size and appearance of which1 ,i infer1 that the fibula would not have become confluent with the tibia1 even in the mature and full-grown animal4 ,the relative length of the fore and hind extremities cannot be precisely determined from the present imperfect skeleton of the ,scelidothere2 but there is good evidence for believing1 that the fore extremity was the shortest4 ,the humerus is shorter than the femur by one-ninth part of the latter bone2 and the radius1 which wants only the distal epiphysis1 must have been shorter than the humerus4 ,now the relative development of the fore and hind legs is one of the points to be taken into consideration in an attempt to determine the habits and nature of an extinct mammal4 ,in climbing animals the prehensile power is more essential to the hinder than to the fore parts or extremities4 ,in the leech the principal sucker is in the tail2 and higher organized climbers1 in like manner1 depend mainly on their posterior claspers in descending trees1 and hold on by means of them whilst selecting the place for the next application of those at the fore part of the body1 whether their place be supplied by the beak1 as in the ,maccaws1 or the fore-feet or hands in the ,mammalia4 ,but1 although we perceive the hinder limbs to be the last to lose the advantageous structure of the hand in the ,quadrumanous species1 and notwithstanding that the tail is for this purpose sometimes specially organized to serve as a prehensile instrument1 yet we find that the power of grasping the branches of trees by either legs or tail is never maintained at the expense of undue bulk and weight of those organs4 ,on the contrary1 as the fore-limbs are the main instruments in the active exertions of climbing1 so they are the strongest as well as the longest in all the best climbers1 and the weight of the body which they have to drag along is diminished by dwarfish proportions of the hinder limbs1 as in the ,orangs and the ,sloths4 ,can those huge quadrupeds have been destined to climb that had the pelvis and hinder extremities more ponderous and bulky in proportion to the fore parts of the body than in any other known existing or extinct vertebrate animals8 ,m4 ,lund argues for the scansorial character of the ,megalonyx1 because its anterior extremities are longer than the posterior ones2 but if they somewhat exceed the hind legs in length1 how vastly inferior are they in respect of their breadth and thickness4 ,the prehensile faculty of the hinder limbs of the best climbers1 as the ,sloths1 ,orangs1 and ,chameleons is by no means dependent on the superior mass of muscle and bone which enters into their conformation1 but is associated with the very reverse conditions4 ,it is impossible to survey the discrepancy of size between the femur and the humerus of the ,scelidothere1 as exhibited in ,pl4 ,,xx41 without a conviction that it relates to other habits than those of climbing trees4 ,the expanse of the sacrum1 the evidence of the muscular masses employed in working the hind legs and tail1 which is afforded by the capacity of the cavity lodging the part of the spinal marrow from which the nerves of those muscles were derived1 both indicate the actions of the hind legs and tail to have been more powerful and energetic than would be required for mere prehension3 and the association of hinder extremities so remarkable for their bulk1 with a long and powerful tail1 forbids my yielding assent to the speculation set forth by ,m4 ,lund1 as to the prehensile character of the tail of the ,megalonyx4 ,astragalus4--,in the examination of this characteristic bone ,i have kept in view the question of the habits of the ,megatherioid quadrupeds in general1 and the especial affinities of the ,scelidotherium1 in illustration of which ,i shall notice at the same time the peculiarities of the astragalus of the ,sloth1 ,megatherium and ,armadillo4#ed ,the upper articular surface of the astragalus of the ,scelidotherium 7,pl4 ,,xxvi4 fig4 #d471 presents1 in its transverse contour1 two convex pulleys1 a and b1 and an intermediate concavity1 forming one continuous articular surface4 ,the external or fibular trochlea 7a7 is strictly speaking convex only at its posterior part1 the upper surface gradually narrowing to a ridge1 as it advances forwards from which1 the inner and outer parts slope away at an angle of #ce4 ,the tibial#ee convexity 7b7 is more regular and less elevated1 it has only half the antero-posterior extent of the outer pulley2 its marginal contour forms an obtuse angle at the inner side4 ,in the ,megatherium the upper articular surface of the astragalus is also divided into two trochle1 of which the one on the fibular side 7fig4 #c1 a71 is of much greater relative size and extent than the tibial one 7b71 and is raised nearly four inches above the level of the latter1 although in the oblique position in which the bone is naturally placed in the skeleton1 the highest part of each convexity is on the same level4 ,the fibular trochlea differs also from that in the ,scelidothere in being regularly convex in the transverse as well as the antero-posterior direction4 ,the tibial convexity resembles that in the ,scelidothere1 save in its smaller relative size2 its internal margin likewise forms an angular projection below the internal malleolus4 ,the upper surface of the astragalus of the ,mylodon1 or ,megalonyx787 7,pl4 ,,xxviii4 fig4 #e471ef differs from that in the ,megatherium in having a narrower fibular trochlear ridge4 ,the astragalus of the ,ai 7,bradypus tridactylus7 differs widely from that of either the ,megathere1 ,mylodon787 or ,scelidothere in having a conical cavity on the upper surface1 in place of the fibular convexity1 in which concavity the distal end of the fibula rotates like a pivot4 ,this mechanism is closely related to the scansorial uses of the inwardly inflected foot of the ,sloth4 ,if the astragalus of an ,armadillo#eg were placed side by side with that of the ,megathere1 it would be very difficult to determine the analogous parts1 especially of the upper surface1 unless guided by the intermediate structure presented by the ,scelidothere4 ,the upper surface of this bone1 in the ,armadillo1 is1 however1 divided into two transversely convex trochle1 separated by a much wider transversely concave surface4 ,the fibular trochlea resembles that of the ,scelidothere in having its upper and outer facets sloping away at an acute angle1 but without meeting at a ridge anteriorly2 this surface is not more raised above the tibial trochlea than in the ,scelidothere4 ,the inner trochlea differs from that of the ,scelidothere in having a greater relative antero-posterior extent1 and in forming1 in place of an uniform convex surface1 a trochlea similar in structure to that on the outer side4 ,the extent of rough surface on the upper part of the astragalus intervening between the articular surface for the bones of the leg1 and that for the scaphoides is extremely small in the ,megathere and ,mylodon7872 it is relatively greater in the ,scelidothere2 it is still more extensive in the ,armadillo2 but is the longest in the ,sloth4 ,the anterior extremity of the astragalus which is entirely occupied by the scaphoid articular surface is very peculiar in the ,scelidothere 7,pl4 ,,xxvi4 fig4 #b473 it presents one convex and two concave facets1 which1 however1 form part of one continuous articular surface3 the convex facet forms the internal part of the surface1 and presents a rhomboidal form with the long axis vertical4 ,the concave facets 7c and d7 are extended transversely and placed one above the other2 they are slightly concave in the transverse1 and nearly flat in the vertical directions4 ,in the ,megatherium 7fig4 #a47 the scaphoid surface of the astragalus is divided only into one concave and one convex portion1 both continuous with each other3 the concave facet 7c7 corresponds with the upper concavity in the ,scelidothere1 but is a pretty uniform subcircular depression1 fourteen lines in depth3 the convex facet1 d1 is continued across the whole breadth of the under part of the scaphoid surface and corresponds with both the inner convex1 and lower concave surfaces of the scaphoid articulation in the ,scelidothere4 ,in the ,mylodon787 7,pl4 ,,xxviii4 fig4 #c471 the articular facet1 corresponding with that marked 7c7 in the astragali of the ,megathere and ,scelidothere1 is simply flattened1 instead of being concave2 the rest of the scaphoid surface corresponds with that in the ,megatherium4 ,in the ,armadillo the scaphoid articular surface is undivided and wholly convex3 in this part of the astragalus1 therefore1 we find the ,scelidothere deviating from the ,armadillo further than does the ,megathere2 while the ,mylodon or ,megalonyx787 most resembles the ,armadillo in the configuration of this part of the astragalus4 ,if we compare the outer surfaces of the astragalus in these quadrupeds1 we shall find1 however1 that the ,scelidothere and ,armadillo closely agree3 the outer facet of the fibular trochle1 above described1 is continued in the ,scelidothere 7,pl4 ,,xxviii4 fig4 #b471 upon the fibular side of the astragalus reaching nearly half-way down the posterior part1 and down nearly the whole of its anterior4 ,in the ,armadillo1 it extends over the whole of the anterior part of the outer side of the astragalus4 ,in both animals the lower boundary of this articular surface describes a strong sigmoid curve4 ,in the ,megatherium 7,pl4 ,,xxviii4 fig4 #a71 the corresponding surface for the fibular malleolus on the outer side of the astragalus is formed by a comparatively very small semicircular flattened facet1 which by its roughness indicates that the end of the fibula was attached to it by ligamentous substance1 and that the synovial bag was not continued upon that surface as in the ,scelidothere and ,armadillo4 ,in the ,mylodon787 7,pl4 ,,xxviii4 fig4 #d71 even this rough facet is wanting and the fibular trochlea is bounded by the angle which divides the upper from the outer surface of the astragalus4 ,turning now our attention to the under surface of the astragalus1 we observe that it presents in the ,scelidothere 7,pl4 ,,xxvi4 fig4 #f71 an irregular quadrate form1 having the outer side occupied by an elongated subovate articular facet1 e1 for the calcaneum1 bounded externally by a sharp edge1 with its long axis and its greatest concavity in the antero-posterior direction1 and slightly convex from side to side3 a second calcaneal articular surface 7f7 is situated at the inner and anterior angle2 it is oblong and nearly flat2 is continuous with the inferior concave facet of the scaphoid articulation1 but is divided from the convex facet by a groove3 the two calcaneal articulations are separated by a deep and rough depression1 traversing the under surface of the astragalus diagonally1 and increasing in breadth towards the posterior and internal angle4 ,the inner side of the astragalus presents a convex protuberance4 ,the correspondence between the astragalus of the ,scelidothere and ,megathere is best seen at the under surface of the bone3 in both the two calcaneal articulations are separated by the diagonal depression1 and the internal and anterior surface is continuous with the scaphoid articulation4 ,in the ,megathere1 however1 in consequence of the absence of the inferior concavity which characterizes the ,scelidothere1 the anterior calcaneal facet 7f7 appears as a more direct backward continuation of the scaphoidal surface2 but they are divided by a more marked angle than is represented in the figure 7fig4 #e1 ,pl4 ,,xxvi474 ,the posterior and outer calcaneal surface in the ,megathere 7e7 is broader in proportion to its length1 continued further upwards upon the outward surface1 is consequently more convex in the transverse direction1 and is not bounded externally by so sharp and prominent a ridge as in the ,scelidothere4 ,the protuberance from the inner surface of the astragalus is more compressed laterally in the ,megathere than in the ,scelidothere4 ,the correspondence between the astragali of the ,mylodon787 7,pl4 ,,xxviii4 fig4 #f7 and ,megathere in the conformation of the under surface is so close1 that the few differences which exist will be sufficiently appreciated by an inspection of the figures4 ,in the ,armadillo the astragalus1 in consequence of the greater production of its anterior part1 presents more of an angular than a quadrate figure2 and the scaphoid articular surface1 being proportionally carried forwards1 is altogether separated from the anterior calcaneal surface4 ,the posterior and inner calcaneal surface resembles that in the ,scelidothere1 but is less inclined upwards2 and is continuous with the posterior part of the tibial articular surface4 ,thus the astragalus in the structure of its two most important articulations1 viz4 that which receives the superincumbent weight from the leg1 and that which transmits it to the heel1 presents a closer correspondence in the ,scelidothere with that of the ,dasypus1 than with that of the ,megathere or ,mylodon4 ,the ungueal phalanx of the ,scelidothere before alluded to1 is represented of the natural size in ,pl4 ,,xxvii4 ,the side view1 fig4 #c4 shows the position of the articular surface on the proximal end1 sloping obliquely towards the under surface1 and overtopped by an obtuse protuberance1 calculated to impede any upward retraction of the claw3 the present joint1 in fact1 illustrates in every particular the argument by which ,cuvier established the true affinities of the allied extinct genus ,megalonyx4#eh ,the present phalanx is1 however1 less compressed1 and less incurved than those of the ,megalonyx1 which have been hitherto described2 but it more resembles in these proportions one of the smaller1 and presumed hinder1 ungueal phalanges of the ,megatherium4 ,the upper and lateral parts of the bone are rounded1 and it gradually tapers to the apex1 which is broken off4 ,the osseous sheath for the claw is developed only at the under part of the bone3 it presents the form of a thick flat plate of bone1 with the margin very regularly and obliquely bevelled off1 and having a vertical process of bone attached lengthwise to the middle of its under surface4 ,this process must have served for the insertion of a very powerful flexor tendon4 ,the figures of this bone preclude the necessity of any further verbal description4 ,m4 ,lund lays most stress upon the argument founded on the inward inflection of the sole of the foot in the ,megalonyx1 and appeals with greatest confidence to this structure in support of his hypothesis of the scansorial habits of that extinct ,edental4#ei ,it is quite true that the ,quadrumana derive advantage from this position of the foot in climbing trees1 and that it is carried to excess in the ,sloths1 which can only apply the outer edge of the foot to the ground4 ,but we may ask1 was the inversion of the sole of the foot actually carried to such an extent in the ,megalonyx8 ,and1 admitting its existence in an inferior degree1 is it then conclusive as to the scansorial habits of that species8 ,m4 ,lund expressly states that it is produced by a different structure and arrangement of the tarsal bones1 from that which exists in the ,sloth1 but he does not specify the nature of this difference4 ,if the astragalus1 which ,i have referred with doubt to the ,megalonyx1 do not actually belong to that genus1 it is evidently part of a very closely allied species4 ,now this astragalus1 as we have seen1 resembles most closely that of the ,megatherium2 and since we may infer that the calcaneum1 scaphoides1 and cuboides had a like correspondence1 the inclination of the sole of the foot inwards must have been very slight1 as ,i have determined from examination of the structure and co-adaptation of those bones in the incomplete skeleton of the ,megatherium in the ,london ,college of ,surgeons4 ,such an inclination of the foot may be conceived to have facilitated the bending of the long claws upon the sole1 during the ordinary progressive movements of the animal1 but it is quite insufficient to justify the conclusion1 that it related to an application of the hind-feet for the purposes of climbing4 ,it is not without interest again to call to mind the deviation of the structure of the astragalus of the ,scelidothere from the ,megatherioid to the ,dasypodoid type of structure4 ,for if the ,megatherioid type of structure had really been one suitable to the exigencies of climbing quadrupeds1 it might have been expected to have exhibited the scansorial modifications more decidedly1 as the species diminished in stature2 but as regards the instructive bone of the hind-foot1 the modifications of which we have just been considering1 this is by no means the case4 ,,description ,,of ,a ,,mutilated ,,lower ,,jaw ,,of ,,the ,,megalonyx ,,jeffersonii4 ,in the preceding section an astralagus was described1 which was regarded as belonging possibly to the same ,edentate species as the jaw figured and described1 p4 #fi1 ,pl4 ,,xviii4 and ,,xix41 under the name of ,mylodon ,darwinii2 but the same correspondence1--that of relative size1--renders it equally possible that this astragalus may belong to the species of ,megalonyx to which the lower jaw now under consideration appertains4 ,there could be no doubt1 from its structure1 that it was the astragalus of a gigantic species of the order ,bruta1 and of the ,megatherioid family1 and more nearly allied to the ,megathere than is the ,scelidothere1 but sufficiently distinct from both4 ,the lower jaw1 figured in ,pl4 ,,xxix41 is the only fossil brought home by ,mr4 ,darwin that could be confidently referred to the genus ,megalonyx2 but the form of the tooth in place on the right side of the jaw fully justifies this determination4 ,the jaw itself is deeply and firmly imbedded in the matrix1 so that only the upper or alveolar border is visible4 ,the coronoid and condyloid processes are broken away1 and the texture of the remaining part of the jaw was too friable1 and adhered too firmly to the surrounding matrix to admit of more of its form being ascertained than is figured4 ,there were four molars on each side of this jaw2 the large oblique perforation near the fractured symphysis is the anterior extremity of the wide dental canal4 ,the forms of the alveoli are best preserved in the right ramus3 the first is the smallest1 and seems to have contained a tooth1 of which the transverse section must have been simply elliptical3 the second tooth is likewise laterally compressed1 but the transverse section is ovate1 the great end being turned forwards3 the third socket presents a corresponding form1 but a larger size3 the fourth socket is too much mutilated to allow of a correct opinion being formed as to the shape of the tooth which it once contained4 ,the natural size of the tooth in situ1 and of the adjoining socket1 is given in ,pl4 ,,xxix41 fig4 #b4 ,the difference of form which the jaw of the ,megalonyx presents1 as compared with that of the ,mylodon1 especially in the greater recedence of the two horizontal rami from each other1 will be appreciated by comparing ,pl4 ,,xviii4 with ,pl4 ,,xxix4 ,,description ,,of ,a ,,fragment ,,of ,,the ,,skull ,,and ,,of ,,the ,,teeth ,,of ,,the ,,megatherium ,,cuvieri4 ,notwithstanding the full1 accurate1 and elaborate accounts of the skeleton of the ,megatherium given by ,bru1#fj ,cuvier1#fa ,pander and ,d',alton1#fb and ,mr4 ,clift1#fc the fragments of this most gigantic of quadrupeds brought home by ,mr4 ,darwin1 possess much interest1 and have added1 what could hardly have been anticipated1 important information as to the dental system1 whereby an error in the generic character of the ,megatherium has been corrected4 ,the fragments here alluded to are portions of the skull of three full-grown ,megatheres3 the most perfect part of which affords a view of the posterior1 and of part of the basal surface1 which regions of the cranium have not hitherto been elsewhere figured or described1 7,pl4 ,,xxx47 ,the plane of the occipital foramen forms with that of the base of the skull an angle of #adj1 the plane of the posterior surface of the skull forms with the basal plane an angle of #fh4 ,the occipital condyles are therefore terminal1 or form the most posterior parts of the cranium4 ,the extent of their convex curvature in the antero-posterior direction1 which equals that of a semicircle1 indicates that the ,megatherium possessed considerable freedom and extent of motion of the head4 ,the condyles are not extended in the lateral direction so far as in the ,toxodon2 their axis is more oblique than in the ,glossotherium1 and their internal surface is more parallel with the axis of the skull1 the foramen magnum not presenting that infundibuliform expansion which is so characteristic of the ,glossotherium4 ,the occipital condyles resemble most in form and position those of the ,scelidotherium2 but in the angle of the occipital plane the ,megatherium is intermediate between the ,scelidothere and ,glossothere4 ,the ex-occipitals terminate laterally and inferiorly1 each in a short1 but strong obtuse process4 ,the posterior plane of the skull is traversed by a strong arched intermuscular crest1 which forms the upper boundary of a pretty deep fossa1 which is divided by a median vertical ridge1 extending downwards to within an inch of the upper margin of the foramen magnum4 ,a second strong obtuse transversely arched ridge curves over the first1 and forms the upper boundary of the posterior or occipital region of the skull3 the interspace between the two transverse ridges is very irregular1 and indicates the firm implantation of powerful nuchal muscles or ligaments1 7,pl4 ,,xxx4 fig4 #a47 ,in the configuration and angle of the occipital plane the ,megatherium indicates the same general correspondence with the ,edentate type1 which has been pointed out in the descriptions of the crania of the ,glossothere and ,scelidothere3 and the resemblance to the ,scelidothere is not less striking in the small proportional size of the cranium in this quadruped1 which surpasses the rest of its class in so great a degree in the colossal proportions of its hinder parts4 ,having detected in the base of the skull of the ,scelidothere an articular semicircular pit for the head of the styloglossal bone1 similar to1 but relatively smaller than1 that remarkable one in the skull of the ,glossothere1 it became a matter of interest to determine whether this structure1 which does not exist in any of the existing ,edentals1 should likewise be present in the gigantic type of the ,megatherioid family4 ,the result of a careful removal of the matrix from the basal region of one of the cranial fragments of the ,megatherium was the detection of this articular cavity1 in each temporal bone in the same relative position as in the ,glossothere and ,scelidothere4 ,the styloid articular cavity is relatively smaller1 and shallower1 than in the ,glossothere1 its proportions being much the same as those of the ,scelidothere4 ,the cranial or posterior extremity of the stylo-hyoid bone in the ,scelidotherium is bent upwards at an obtuse angle 7,pl4 ,,xxi471 and terminates in an articular ball which rotates in this cavity4 ,the size of this bone1 and its mode of articulation1 indicates great power and muscularity of tongue in the ,megatherioids1 and calls to mind the importance of that organ in the ,giraffe1 which subsists on the same kind of food as that which ,i have supposed to have supported the ,megatherioids1 although the general organization of these animals and the mode in which the foliage was brought within reach of the tongue are as opposite as can well be imagined4 ,the anterior condyloid foramen presents scarcely one-half the absolute size of that of the ,glossothere1 whence we may infer a correspondingly inferior development of the tongue in the ,megathere4 ,the fractured parietes of the cranial cavity of the ,megatherium every where exhibit evidences of the great extent of the air-cells or sinuses continued from the nasal cavity3 on the basilar aspect of the cranium they extend as far back as the jugular foramina3 the whole of the basi-sphenoid being thus excavated1 and permeable to air1 derived from the sphenoid sinuses1 7,pl4 ,,xxx4 fig4 #b474 ,the vertical diameter of the cranial cavity is four inches1 eight lines2 its transverse diameter1 which is greatest in the posterior third part of the cavity1 corresponding with the posterior part of the cerebrum is six inches3 from the indications afforded by the remains of the cranial cavity in ,mr4 ,darwin's specimens1 ,i conclude that the brain of the ,megatherium was more depressed1 and upon the whole1 smaller by nearly one-half than that of the ,elephant2 but with the cerebellum relatively larger1 and situated more posteriorly with relation to the cerebral hemispheres3 whence it may be concluded that the ,megatherium was a creature of less intelligence1 and with the command of fewer resources1 or a less varied instinct than the ,elephant4 ,it has been usual to characterize the ,megatherium1 in conformity with the concurrent descriptions of ,bru1 ,cuvier1 and ,d',alton1 by the dental formula of molares 1 i4 e4 by the presence of four grinding teeth on each side of the upper1 as of the lower jaw4 ,it was the agreement of the excellent authorities above cited in this statement1 which induced ,mr4 ,clift and myself to regard a single detached tooth1 which formed part of the valuable collection of remains of the ,megatherium deposited in the ,hunterian ,museum by ,sir ,woodbine ,parish1 as being1 from its comparatively small size1 the tooth of either a younger individual or of a smaller species of ,megatherium4 ,upon clearing away the matrix from the palatal and alveolar surface of one of the cranial fragments of the ,megatherium in ,mr4 ,darwin's collection1 ,i was gratified by the detection of the crown of a fifth molar1 corresponding in size and form with the detached tooth1 above alluded to3 its small size1 and its position have doubtless occasioned its being over-looked in the cranium of the great skeleton at ,madrid4 ,the anterior molar of the upper jaw presents a nearly semicircular transverse section1 with the angles rounded off2 the three succeeding teeth are four-sided1 with the transverse somewhat exceeding the antero-posterior diameter3 they are rather longer and larger than the first3 the last molar is likewise four-sided1 but presents a sudden diminution of diameter1 and is relatively broader4 ,the following are the respective dimensions of the upper maxillary teeth4 ,first ,second ,third ,fourth ,fifth ,molar4 ,molar4 ,molar4 ,molar4 ,molar4 ,in4 ,lines4 ,in4 ,lines4 ,in4 ,lines4 ,in4 ,lines4 ,in4 ,lines4 ,length #h #f #i #d #i #d #h #g #e #b ,transverse #a #i #b #d #b #c #b #j #a #d diameter ,antero-posterior #a #e #b #j #b #j #a #aa #j #aj diameter ,besides the differences in size1 the upper molars vary as to their curvature3 this difference is exhibited in the vertical section of these teeth figured in ,pl4 ,,xxxi4 ,the convexity of the curve of the first1 second and third molars is directed forwards2 the fourth is straight1 its anterior surface only describing a slight convexity in the vertical direction2 the fifth tooth is curved1 but in a contrary direction to the others2 and the bases of the five molars thus present a general convergence towards a point a little way behind the middle of the series4 ,the next peculiarity to be noticed in these remarkable teeth is the great length of the pulp-cavity 7d71 the apex of which is parallel with the alveolar margin of the jaw3 a transverse fissure is continued from this apex to the middle concavity of the working surface of the tooth1 which is thus divided into two parts4 ,each of these parts consists of three distinct substances1--a central part analogous to the body or bone of the tooth or #8dentine1' a peripheral and nearly equally thick layer of cmentum1 and an intermediate thinner stratum of a denser substance1 which is described in ,mr4 ,clift's memoir on the ,megatherium as #8enamel1' and to which substance in the compound teeth of the ,elephant1 it is analogous both in its relative situation1 and relative density to the other constituents4 ,microscopic examinations of thin and transparent slices of the tooth of the ,megatherium prove1 however1 that the dense layer separating the internal substance from the cmentum is not enamel1 but presents the same structure as the hard #8dentine' or ivory of the generality of ,mammalian teeth2 and corresponds with the thin cylinder of hard #8dentine' in the tooth of the ,sloth4 ,no species of the ,order ,bruta has true enamel entering into the composition of its teeth2 but the modifications of structure which the teeth present in the different genera of this order are considerable1 and their complexity is not less than that of the enamelled teeth of the ,herbivorous ,pachyderms and ,ruminantia1 in consequence of the introduction of a dental substance into their composition corresponding in structure with that of the teeth of the ,myliobates1 ,psammodus1 and other cartilaginous fishes4 ,the microscopic investigation of the structure of the teeth of the ,megatherium was undertaken chiefly with the view of comparing this structure with that of the teeth of the ,sloth and ,armadillo1 and of thus obtaining an insight into the food1 and an additional test of the real nature of the disputed affinities of the ,megatherium4 ,the central part of the tooth 7c4 ,pl4 ,,xxxi47 consists of a coarse ivory1 like the corresponding part of the tooth of the ,sloth4 ,it is traversed throughout by medullary canals of an inch in diameter1 which are continued from the pulp-cavity1 and proceed1 at an angle of #ej1 to the plane of the dense ivory1 parallel to each other1 with a slightly undulating course1 having regular interspaces1 equal to one and a half diameters of their own are1 and generally anastomosing in pairs by a loop of which the convexity is turned towards the origin of the tubes of the fine dentine1 as if each pair so joined consisted of a continuous reflected canal1 7c4 fig4 #a1 ,pl4 ,,xxxii47 ,the loops are generally formed close to the fine dentine4 ,in a few situations ,i have observed one of the medullary canals continued across the fine dentine1 and anastomosing with the corresponding canals of the cmentum4 ,the interspaces of the medullary canals of the coarse dentine are principally occupied by calcigerous tubes which have an irregular course1 anastomose reticularly1 and terminate in very fine cells4 ,the more regular and parallel calcigerous tubes1 which constitute the thin layer of hard dentine1 are given off from the convexity of the terminal loops of the medullary canals4 ,the course of these tubes 7b4 fig4 #a1 ,pl4 ,,xxxii47 is rather more transversely to the axis of the tooth than the medullary canals from which they are continued4 ,they run parallel to each other1 but with minute undulations throughout their course1 in which they are separated by interspaces equal to one and a half their own diameter4 ,as they approach the cmentum they divide and sub-divide1 and grow more wavy and irregular3 their terminal branches take on a bent direction1 and form anastomoses1 dilate into small cells1 and many are seen to become continuous with the radiating fibres or tubes of the cells or corpuscles of the contiguous cmentum4 ,this substance enters largely into the constitution of the compound tooth of the ,megatherium3 it is characterized1 like the cmentum of the ,elephant's grinder1 by the presence of numerous radiated cells1 or purkingian corpuscles1 scattered throughout its substance1 but may be distinguished by wide medullary canals which traverse it in a direction parallel with each other1 and forming a slight angle with the transverse axis of the tooth4 ,these canals are wider than those of the central coarse dentine1 their diameter being th of an inch2 they are separated by interspaces equal to from four to six of their own diameters1 divide a few times dichotomously in their course1 and finally anastomose in loops1 the convexity of which is directed towards1 and in most cases is in close contiguity with1 the layer of dense dentine4 ,fine calcigerous tubes are every where given off at right angles from the medullary canals of the cmentum1 which form a rich reticulation in their interspaces1 and a direct continuation between the loops of the medullary canals and the calcigerous tubes of the dense dentine4 ,the cmentum differs from the coarse dentine in the larger size and wider interspaces of its medullary canals1 and by the presence of the bone-corpuscles in their interspaces2 but they are brought into organic communication with each other1 not only by means of the tubes of the dense dentine1 but by occasional continuity of the medullary canals across that substance4 ,the tooth of the ,megatherium thus offers an unequivocal example of a course of nutriment from the dentine to the cmentum1 and reciprocally4 ,retzius observes with respect to the human tooth1 that 8the fine tubes of the cmentum enter into immediate communications with the cells and tubes of the dentine 7zahnknochen71 so that this part can obtain from without the requisite humours after the central pulp has almost ceased to exist40 ,in the ,megatherium1 however1 those anastomoses have not to perform a vicarious office1 since the pulp maintains its full size and functional activity during the whole period of the animal's existence4 ,it relates to the higher organized condition1 and greater degree of vitality of the entire grinder in that extinct species4 ,the conical cavities 7d4 ,pl4 ,,xxxi47 attest the size and form of the persistent pulp2 the diameter of its base is equal to the part of the crown of the tooth which is formed by the coarse and fine dentine4 ,from the gradual thinning off and final disappearance of these substances as they reach the base of the tooth1 ,i conclude that they were both formed at the expense of the pulp4 ,the fine tubes and cells must have been excavated in its peripheral layer for the reception of the hardening salts of the dense dentine1 and the rest converted into the parallel series of medullary canals with their respective systems of calcigerous tubes1 in a manner closely analogous to the development of the entire tooth of the ,orycteropus4 ,the coarser dentine of the tooth of the ,megatherium differs1 in fact1 from the entire tooth of the ,orycteropus1 only in that the parallel medullary canals and their radiating calcigerous tubes are not separated from the contiguous canals by a distinct layer of cmentum1 and that the medullary canals anastomose at their peripheral extremities4 ,the wide spaces1 7e4 ,pl4 ,,xxxi47 indicate the thickness of the dental capsule by the ossification of which the exterior stratum of cement was formed4 ,it was not until ,i knew the true structure of the tooth of the ,megatherium1 that ,i could comprehend the mode of its formation4 ,the parallel layers of enamel in the ,elephant's grinder are formed1 as is well known1 by membranous plates passing from the coronal end of the closed capsule towards the base of the tooth2 but a certain extent of enamel can only thus be formed1 and when the crown of the grinder has once protruded1 and come into use1 the enamel cannot be added to4 ,the modification of the structure of the tooth of the ,megatherium readily permits the uninterrupted and continuous formation of the dense substance which is analogous to the enamel of the ,elephant's grinder4 ,with respect to the question of the respective affinities of the ,megatherium to the ,bradypodoid or ,dasypodoid families1 the result of this examination of the teeth speaks strongly for its closer relationship with the former group3 the ,megalonyx1 ,mylodon1 and ,scelidotherium1 in like manner correspond in the structure of their teeth with the ,sloth1 and differ from the ,armadillo4 ,if from a similarity of dental structure we may predicate a similarity of food1 it may reasonably be conjectured that the leaves and soft succulent sprouts of trees may have been the staple diet of the ,megatherioid quadrupeds1 as of the existing ,sloths4 ,their enormous claws1 ,i conclude1 from the fossorial character of the powerful mechanism by which they were worked1 to have been employed1 not1 as in the ,sloths1 to carry the animal to the food1 but to bring the food within the reach of the animal1 by uprooting the trees on which it grew4 ,in the remains of the ,megatherium we have evidence of the frame-work of a quadruped equal to the task of undermining and hauling down the largest members of a tropical forest4 ,in the latter operation it is obvious that the immediate application of the anterior extremities to the trunk of the tree would demand a corresponding fulcrum1 to be effectual1 and it is the necessity for an adequate basis of support and resistance to such an application of the fore extremities which gives the explanation to the anomalous development of the pelvis1 tail1 and hinder extremities in the ,megatherioid quadrupeds4 ,no wonder1 therefore1 that their type of structure is so peculiar2 for where shall we now find quadrupeds equal1 like them1 to the habitual task of uprooting trees for food8 ,,description ,,of ,,fragments ,,of ,,bones1 ,,and ,,of ,,osseous ,,tesselated ,,dermal ,,covering ,,of ,,large ,,edentata4 ,it is now determined that there once existed in ,south ,america1 besides the ,megatherium1 the ,megalonyx1 and the allied genera described in the preceding pages of the present work1 gigantic species of the order ,bruta belonging to the ,armadillo family1 and defended1 like the small existing representatives of that family1 by a tesselated bony dermal covering4 ,the largest known species of these extinct ,dasypodid is the ,glyptodon clavipes1 of which the armour and parts of the skeleton have been described by ,,mm4 ,weiss and ,d',alton in the ,berlin ,transactions for #ahbg and #ahcd3 and the generic and specific characters and name1 with an account of the dental system1 and bones of the extremities1 were recorded in the ,geological ,proceedings for ,march #ahci4 ,it would seem that parts of the same1 or a nearly allied gigantic species were described in the same year by ,m4 ,lund2 under the name of ,hoplophorus4 ,of the valuable and interesting discoveries of this able ,naturalist ,i regret that ,i was not aware until the appearance of a notice of them in the ,comptes ,rendus for ,april1 #ahci4fd ,amongst the fragments of bony tesselated armour in ,mr4 ,darwin's collection are a few pieces which were found by him1 associated with remains of ,toxodon and ,glossotherium near the ,rio ,negro in ,banda ,oriental4#fe ,these fragments1 if we may judge from their thickness1 must have belonged to an animal at least as large as the ,glyptodon clavipes2 but the pattern differs in the greater equality of size of the component tesser4 ,the thickness of the largest fragment is one inch and a half1 the tesser vary in diameter from one inch to half an inch1 and are separated by grooves about two lines in depth1 and two in diameter4 ,the pattern formed by the anastomosis of these grooves is an irregular net-work2 the contour of the tesser is either unevenly subcircular1 hexagonal1 pentagonal1 or even four-sided2 with the sides more or less unequal4 ,in those portions of this armour1 where one of the tesser exceeds the contiguous ones in size1 the imagination may readily conceive it to be the centre of a rosette1 around which the smaller ones arrange themselves1 but there is no regular system of rosettes1 as in the portions of the dermal armour of the ,glyptodon figured by ,weiss1 and those brought to ,england by ,sir ,woodbine ,parish1 in which the central piece is double the size of the marginal ones4 ,the portions of the tesselated bony dermal covering of a ,dasypodoid quadruped1 figured in ,pl4 ,,xxxii4 figs4 #e and #d1 of the natural size1 were discovered folded round the middle and ungueal phalanges1 figs4 #b and #c1 at ,punta ,alta1 in ,bahia ,blanca1 in an earthy bed interstratified with the conglomerate containing the remains of the fossil ,edentals4 ,in one of these fragments1 measuring six inches long by five broad1 the tesser are arranged in rosettes1 and so closely correspond in size and pattern with the bony armour described by ,m4 ,lund1 as characterizing his species1 ,hoplophorus euphractus1 that ,i feel no hesitation in referring them to that animal4 ,one of the pattern rosettes is figured at fig4 #d1 together with the thickness of the armour at this part1 and the coarse tubulo-cellular structure of the bone4 ,another portion of dermal armour from the same locality1 gives the pattern shown in fig4 #e1 formed by square or pentagonal tesser1 arranged in transverse rows2 it is certain that this portion of armour belonged to the same animal as the preceding piece2 and probably that it constituted part of the transverse dorsal bands of the ,hoplophorus4 ,the middle and ungueal phalanx1 as well as the portions of armour1 are given of the natural size1 in ,pl4 ,,xxxii4 ,the upper and outer surface of the phalanx1 is shown in fig4 #b4 ,it is smooth and flat2 joins the inner surface by a sharp edge1 which runs along the upper and inner side of the bone2 and passes by a gradual convexity to the under surface2 the ridge corresponding with the base of the claw1 is feebly developed at the under and lateral parts of the base of the claw4 ,below the double trochlear joint for the middle phalanx1 there are two articular surfaces for two large sesamoid bones4 ,the middle phalanx corresponds in its small antero-posterior diameter and wedge-shape1 with that of the great ,glyptodon3 but the terminal phalanx is longer and deeper1 in proportion to its breadth4 ,among the collection of fossils from ,punta ,alta1 in ,bahia ,blanca1 there is an interesting fragment of the head of a gigantic animal of the ,edentate order1 including the glenoid cavity1 and part of the zygomatic process of the left side4 ,the articular surface for the lower jaw1 exhibits1 in its flatness1 extent1 and the absence of a posterior ridge1 the well-marked characteristics of this part of the ,edental structure4 ,it measures two inches four lines in the transverse1 and two inches two lines in the antero-posterior diameter4 ,the commencement of the zygomatic process presents a vertical diameter of two inches1 and a transverse diameter of eight lines at the thickest part4 ,it is slightly concave at its lower border1 and convex above4 ,the small portion of the cranial parietes1 which is preserved1 exhibits the cellular structure consequent upon the great extension and development of the nasal air-sinuses3 this condition of the cranial parietes1 has already been noticed in the description of the more perfect skulls of the large extinct ,edentata4 ,,notice ,,of ,,fragments ,,of ,,molar ,,teeth ,,of ,a ,,mastodon4 ,of the remains of this gigantic extinct ,pachyderm1 observed by ,mr4 ,darwin at ,santa ,f1 in ,entre ,rios1 and on the banks of the ,tercero1 the fragments of the teeth and portions of the skeleton which reached ,england1 are not sufficient to lead to a determination of the species2 but sufficiently prove it to have been nearly allied1 if not identical1 with the ,mastodon angustidens of ,cuvier1 and unquestionably distinct from the ,mastodon giganteum of the ,united ,states4 ,,notice ,,of ,,the ,,remains ,,of ,a ,,species ,,of ,,equus1 ,found associated with the extinct ,edentals and ,toxodon at ,punta ,alta1 in ,bahia ,blanca1 and with the ,mastodon and ,toxodon at ,santa ,f1 in ,entre ,rios4 ,the first of these remains is a superior molar tooth of the right side2 it was embedded in the quartz shingle1 formed of pebbles strongly cemented together with calcareous matter1 which adhered as closely to the tooth in question1 as the corresponding matrix did to the associated fossil remains4 ,the tooth was as completely fossilized as the remains of the ,mylodon1 ,megatherium1 and ,scelidothere2 and was so far decomposed1 that in the attempt to detach the adherent matrix1 it became partially resolved into its component curved lamell4 ,every point of comparison that could be established proved it to differ from the tooth of the common ,equus ,caballus only in a slight inferiority of size4 ,the second evidence of the co-existence of the horse with the extinct ,mammals of the tertiary epoch of ,south ,america reposes on a more perfect tooth1 likewise of the upper jaw1 from the red argillaceous earth of the ,pampas at ,bajada de ,santa ,f1 in the ,province of ,entre ,rios4#ff ,this tooth is figured at ,pl4 ,,xxxii4 fig4 #ac and #ad1 from which the anatomist can judge of its close correspondence with a middle molar of the left side of the upper jaw4 ,this tooth agreed so closely in colour and condition with the remains of the ,mastodon and ,toxodon1 from the same locality1 that ,i have no doubt respecting the contemporaneous existence of the individual horse1 of which it once formed part4 ,this evidence of the former existence of a genus1 which1 as regards ,south ,america1 had become extinct1 and has a second time been introduced into that ,continent1 is not one of the least interesting fruits of ,mr4 ,darwin's palontological discoveries4 ,,description ,,of ,,remains ,,of ,,rodentia1 ,,including ,,the ,,jaws ,,and ,,teeth ,,of ,,an ,,extinct ,,species ,,of ,,ctenomys4 ,the fragment of the upper jaw1 figured in ,pl4 ,,xxxii4 fig4 #f1 exhibits the first and second molar in situ1 and the socket of the third and fourth molar1 of a ,rodent1 which by the form and number of the upper maxillary teeth is referable to the genus ,ctenomys4 ,the molars are a little larger1 the longitudinal groove on their external surface is somewhat deeper1 and the last molar is relatively wider than in the existing subterraneous species1--the ,tucutucu 7,ctenomys ,brasiliensis1 ,bl471 of whose habits so interesting an account is given in the description of the ,mammalia of the present ,collection 7,no4 ,,iv4 p4 #gi74 ,the form of the grinding surface of the first and second upper molar is shown below the fig4 #f1 and three views of the second grinder are given at figs4 #g1 #h1 and #i4 ,the fragment of the lower jaw of the same fossil ,rodent is figured at fig4 #aj and #aa4 ,the long anterior incisor is relatively narrower than in the ,ctenomys ,brasiliensis4 ,i have not had the means of comparing this fossil with the ,ctenomys ,magellanicus2 but since it is probable that the ,ct4 ,magellanicus may not be specifically different from the ,ct4 ,brasiliensis1 it may be concluded that the present fossil is equally distinct from both4 ,the portion of the right hind-foot of the ,rodent figured at fig4 #ab1 includes the calcaneum1 astragalus1 cuboides1 external and middle cuneiform bones1 and the metatarsals and proximal phalanges of the toes corresponding with the three middle toes of five-toed quadrupeds4 ,the metatarsals are chiefly remarkable for the well-developed double-trochlear articular surface1 and intermediate ridge4 ,these remains1 as well as the jaws and teeth of the ,ctenomys1 were discovered at ,monte ,hermoso in ,bahia ,blanca4 ,in the same reddish earthy stratum of that locality1 ,mr4 ,darwin discovered the decomposed molar of a ,rodent1 equalling in size1 and closely resembling in the disposition of its oblique component lamin1 the hinder molar of the ,capybara 7,hydrochrus74 ,the fossil differs1 however1 in the greater relative breadth of the component lamin4 ,i have1 lastly1 to notice the head of a femur1 and some fragments of pelvic bones from the same formation which bear the same proportion to the tooth above alluded to1 as subsists between the teeth and bones of the ,capybara1 and which are sufficient to prove that there once has existed in ,south ,america a species of the family ,caviid1 as large as the present ,capybara1 but now apparently extinct4 ,this fact1 together with the greater part of those which have been recorded in the foregoing pages of the present work1 establishes the correspondence1 in regard to the characteristic type1 which exists between the present and extinct animals of the ,south ,american ,continent3 we have abundant evidence likewise of the greater number of generic and specific modifications of these fundamental types which the animals of a former epoch exhibited1 and also of the vastly superior size which some of the species attained4 ,at the same time it has been shewn that some of the present laws of the geographical distribution of animals would not have been applicable to ,south ,america1 at the period when the ,megatherioids1 ,toxodon1 and ,macrauchenia existed3 since the ,horse1 and according to ,m4 ,lund1 the ,antelope and the ,hyna1 were then associated with those more strictly ,south ,american forms4 ,the ,horse1 which1 as regards the ,american continent1 had once become extinct1 has again been introduced1 and now ranges in countless troops over the pampas and savannahs of the new world4 ,if the small ,opossums of ,south ,america had been in like manner imported into ,europe1 and were now established like the ,squirrels and ,dormice in the forests of ,france1 an analogous case would exist to that of the ,horse in ,south ,america1 as the fossil ,didelphys of ,montmartre proves4 ,with respect to the geological contemporaneity of the fossils collected by him1 ,mr4 ,darwin subjoins the following observations3-- 8,the remains of the following animals were embedded together at ,punta ,alta in ,bahia ,blanca3--,the ,megatherium ,cuvierii1 ,megalonyx ,jeffersonii1 ,mylodon ,darwinii1 ,scelidotherium leptocephalum1 ,toxodon ,platensis 787 a ,horse and a small ,dasypodoid quadruped1 mentioned p4 #ajg2 at ,st4 ,f in ,entre ,rios1 a ,horse1 a ,mastodon1 ,toxodon ,platensis1 and some large animal with a tesselated osseous dermal covering2 on the banks of the ,tercero the ,mastodon1 ,toxodon1 and1 according to the ,jesuit ,falkner1 some animal with the same kind of covering2 near the ,rio ,negro in ,banda ,oriental1 the ,toxodon ,platensis1 ,glossotherium1 and some animal with the same kind of covering4 ,to these two latter animals the ,glyptodon clavipes1 described by ,mr4 ,owen in the ,geological ,transactions1 may1 from the locality where it was discovered1 and from the similarity of the deposit which covers the greater part of ,banda ,oriental1 almost certainly be added1 as having been contemporaneous4 ,from nearly the same reasons1 it is probable that the ,rodents found at ,monte ,hermoso in ,bahia ,blanca1 co-existed with the several gigantic mammifers from ,punta ,alta4 ,i have1 also1 shown in the ,introduction1 that the ,macrauchenia ,patachonica1 must have been coeval1 or nearly so1 with the last mentioned animals4 ,although we have no evidence of the geological age of the deposits in some of the localities just specified1 yet from the presence of the same fossil mammifers in others1 of the age of which we have fair means of judging1 7in relation to the usual standard of comparison1 of the amount of change in the specific forms of the invertebrate inhabitants of the sea17 we may safely infer that most of the animals described in this volume1 and likewise the ,glyptodon1 were strictly contemporaneous1 and that all lived at about the same very recent period in the earth's history4 ,moreover1 as some of the fossil animals1 discovered in such extraordinary numbers by ,m4 ,lund in the caves of ,brazil1 are identical or closely related with some of those1 which lately lived together in ,la ,plata and ,patagonia1 a certain degree of light is thus thrown on the antiquity of the ancient ,fauna of ,brazil1 which otherwise would have been left involved in complete darkness40 ,,london3 ,,printed ,,by ,,stewart ,,and ,,murray1 ,,old ,,bailey4 ,illustration3 ,pl4 ,i4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,base of the ,skull of ,taxodon ,platensis4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,ii4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,side ,view of the ,skull of ,taxodon4 ,one-third the ,natural ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,iii4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,top ,view of the ,skull of the ,taxodon4 ,one-third the ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,iv4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,taxodon ,platensis4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,v4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,fragments of the lower ,jaw and ,teeth of a ,taxodon4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,vi4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,cervical ,vertebr of ,macrauchenia4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,vii4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,cervical ,vertebr of #a1 #b4 ,macrauchenia #c1d ,auchenia4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,viii4 ,g4 ,scharf del et lithog4 ,lumbar ,vertebr1 ,macrauchenia4 ,fig4 #a4 ,posterior ,view of last lumbar4 ,fig3 #b1cd4 ,fourth lumbar ,vertebra4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,ix4 ,lithog4 from ,nature by ,g4 ,scharf4 ,macrauchenia4 ,fig4 #ab4 ,scapula4 ,fig4 #c4 ,femur4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,x4 ,g4 ,scharf del et lithog4 ,proximal ,extremity of anchylosed ,ulna and ,radius ,macrauchenia4 ,nat4 ,size4 ,london1 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xi4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,bones of the right fore-foot1 ,macrauchenia4 ,fig4 #a1 1 #bi1 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,nat4 ,size4 ,right ,femur4 ,macrauchenia4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xiii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,macrauchenia4 ,right ,tibia and ,fibula4--,fig4 #bd4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xiv4 ,lithog4 from ,nature by ,g4 ,scharf4 ,right ,astragalus41 ,macrauchenia4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xv ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,macrauchenia4 ,fig4 #a4 ,metatarsal4 #be4 ,metacarpals4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xvi4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,fragment of the ,cranium of the ,glossotherium ,nat4 ,size4 ,illustration3 ,pl4 ,,xvii4 ,fig4 #c4 #d4 ,laurillard del4 ,fig4 #e4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 #a4 ,megalonyx ,jeffersoni4 #b4 ,meg4 laqueatus4 #c4 #d4 ,mylodon ,harlani4 #e4 ,myl4 ,darwinii4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xviii ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,mylodon4 ,nat ,size4 ,illustration3 ,pl4 ,,xix ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,mylodon4 ,fig #a4 ,nat4 ,size4 ,fig4 #b4c4d4 ,nat4 ,size4 ,illustration3 ,pl4 ,,xx4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,scelidotherium4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xxi4 ,g4 ,scharf del et lithog4 ,printed by ,c4 ,hullmandel4 ,scelidotherium4 ,fig #a #b ,nat4 ,size4 ,fig #ce4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,xxii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,scelidotherium4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill1 ,london4 ,illustration3 ,pl4 ,,xxiii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,cranial ,cavity and ,dentition of ,scelidotherium4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xxiv4 ,lithog4 from ,nature by ,g4 ,scharf4 ,cervical and ,anterior dorsal ,vertebr ,fig3 #a4 ,scelidothere4 ,fig3 #b4 ,orycterope4 ,fig3 #c4 ,armadillo4 ,fig3#d4 ,great ,ant-eater4 ,one-third ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xxv4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,scelidotherium ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xxvi4 ,printed by ,c4 ,hullmandel4 ,left ,astragalus ,fig4 #a4c4e4 ,megatherium3 ,nat4 ,size4 #b4d4f ,scelidotherium4 ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xxvii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,scelidotherium4 ,fig4 #a4b4 ,nat4 ,size4 #c4d4e ,nat4 ,size4 ,published by ,smith1 ,elder ,c #fe1 ,cornhill4 ,illustration3 ,pl4 ,,xxviii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,left ,astragalus4 ,fig4 #a4 ,megatherium4 ,nat4 ,size4 ,fig3 #b4 ,scelidotherium4 ,nat4 ,size4 ,fig4 #c-f1 ,mylodon48 ,nat4 ,size4 ,illustration3 ,pl4 ,,xxix4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,lower ,jaw of ,megalonyx4 ,fig4 #a4 4 ,fig4 #b4 ,nat4 ,size4 ,illustration3 ,pl4 ,,xxx4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,megatherium ,nat4 ,size ,illustration3 ,pl4 ,,xxxi4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 ,section of the superior maxillary teeth1 ,megatherium4 ,nat4 ,size4 ,illustration3 ,pl4 ,,xxxii4 ,lithog4 from ,nature by ,g4 ,scharf4 ,printed by ,c4 ,hullmandel4 #a4 ,megatherium4 #be4 ,hoplophorus4 #fab4 ,ctenomys4 #acad4 ,equus4 ----- ,footnote #a3 ,see ,ossemens ,fossiles1 ,ed4 iv4 tom4 ii4 p4 #cfh4 ,pl4 #bg4 fig #a4 #ab4 ,footnote #b3 ,ibid4 p4 #cgj4 ,pl4 #bg4 fig4 #e4 ,footnote #c3 ,ibid4 p4 #cdg1 #cfg4 ,footnote #d3 ,ibid4 p4 #ccg4 ,pl4 #bf4 fig4 #g4 ,footnote #e3 ,philosophical ,transactions1 vol4 lviii4 p4 #cd4 7#agfh47 ,footnote #f3 ,bridgewater ,treatise1 p4 #aci4 ,footnote #g3 ,geological ,transactions1 vol4 iii4 p4 #dcg4 pl4 #dd1 #de1 #df4 ,footnote #h3 ,quoted by ,cuvier1 ,ossem4 ,foss4 ,ed4 iv4 tom4 ii4 p4 #cea4 ,footnote #i3 1 arcus2 1 dens4 ,footnote #aj3 ,mem4 de l',acad4 des ,sciences de ,paris1 #agfd1 p4 #efh4 ,footnote #aa3 ,true fangs exist only in teeth of temporary growth1 they may be one or more in number1 but always diminish in size as they recede from the crown of the tooth1 and are either solid1 or with a very small canal4 ,footnote #ab3 ,this was written before an examination of the fragment of a lower jaw1 forming part of ,mr4 ,darwin's collection of ,fossil ,remains1 had led me to suspect that it was referrible to the genus ,toxodon2 should this suspicion prove correct1 the four unequal incisors of the upper jaw are opposed to six equal sized ones in the lower4 ,footnote #ac3 ,i have ascertained that this elastic ligament exists in the neck of the ,dugong4 ,footnote #ad3 ,the ,german ,translator 7,see ,frorieps ,notizen41 #ahcg1 p4 #aai7 of the abstract of my description of the ,toxodon1 published in the ,proceedings of the ,geological ,society1 asks1 what is the ,mutica 7misprinted ,muticata71 of ,linnus8 ,the term is quoted from the ,systema ,natur1 ,ed4 xii4 p4 #bd4 ,linnus first divides ,mammalia into three groups1 according to modifications of the locomotive organs1 viz4 ,unguiculata1 ,ungulata1 ,mutica1 and subdivides these1 according to modifications of the dentary organs1 into the orders1 ,bruat1 ,glires1 ,primates1 c4 ,footnote #ae3 ,besides the relation to food requiring much comminution1 which teeth with persistent pulps bear1 they are also connected with the longevity of the individual4 ,the term of life in a herbivorous animal1 with grinders of temporary growth1 is1 of necessity1 dependent on the duration of these essential aids to nutrition2 thus1 a sheep generally wears down its grinders in twelve years1 and its natural term of life is consequently limited to about that period4 ,footnote #af3 longus1 cervix3 from the latter word ,illiger derived ,auchenia1 his generic name of the ,llama1 ,vicugna1 c4 ,footnote #ag3 ,in the seventh cervical vertebra of the ,camel1 as in many other ,mammalia1 there is no perforation in any part for the vertebral arteries4 ,in a ,vicugna1 ,i find the same structure2 but in a ,llama1 the side of the body of the seventh cervical vertebra is perforated longitudinally on the right side4 ,in the ,camel1 the vertebral arteries pierce the sixth cervical vertebra1 immediately below the superior transverse processes1 and pass obliquely to the anterior aperture of the cervical canal1 where they emerge beneath the anterior oblique processes1 and then enter the spinal canal of the fifth cervical vertebra1 as described in the text4 ,footnote #ah3 ,cuvier1 ,ossemens ,fossiles1 iii4 p4 #bch4 ,footnote #ai3 ,loc4 cit4 p4 #bcd4 ,footnote #bj3 ,loc4 cit4 p4 #bce4 ,footnote #ba3 ,loc4 cit4 p4 #bcg4 ,footnote #bb3 ,loc4 cit4 p4 #bcb4 ,footnote #bc3 ,see ,ossem4 ,fossiles1 ,pl4 ,,xx4 fig4 #c4 ,footnote #bd3 ,loc4 cit4 ,pl4 ,,xxii4 fig4 #f4 ,footnote #be3 ,see ,ossem4 ,foss4 iii4 ,pl4 ,,xxvi4 fig4 #e4 ,footnote #bf3 ,this diameter increases rapidly in the posterior lumbar vertebr1 in correspondence with the enlargement of the spinal chord1 which gives off the great nerves of the hinder extremities4 ,footnote #bg3 ,the relative breadth of these bones is shown in the figures of the fore-foot1 ,pl4 ,,xi4 ,footnote #bh3 ,the figures in ,pl4 ,,xiv4 preclude the necessity of giving the admeasurements of the astragalus4 ,footnote #bi3 8,comme le genre de vie de chaque animal est toujours en rapport avec les mouvements dont sa mchoire est susceptible1 on retrouve dans la conformation des surfaces destines l'articulation1 les particularits qui semblent le dterminer d'avance4 ,ainsi dans les animaux qui vivent de chairs1 substances filamenteuses qui ne peuvent tre crases1 mais seulement coupes et dechires1 le mouvement de la mchoire infrieure ne peut s'excuter que de haut en bas4 ,dans les herbivores1 les frugivores et les granivores1 comme le principal mouvement est celui de broiement pour craser1 comprimer les herbes et les fruits1 pour briser les grains et les rduire1 en pte1 le mouvement des mchoires se fait encore de droite gauche1 et rciproquement1 on en mme temps1 de devant en arrire1 en un mot1 dans un plan horizontal autant que dans un vertical3 les uns reprsentent des ciseaux1 les autres des meules de moulin40 ,footnote #cj3 ,in the monotrematous ,echidna1 the large canal for the lingual nerve has a widely different direction and course from that in the placental ,edentata4 ,footnote #ca3 ,transactions of the ,philosophical ,society of ,philadelphia1 vol4 iv4 p4 #bdf4 ,footnote #cb3 ,its relations to the ,edentata1 previously conjectured by ,dr4 ,wistar1 are proved in the ,annales du ,musum1 tom4 v4 p4 #ceh2 its more immediate affinities as an annectant form in that group are discussed in the edition of the ,ossem4 ,fossiles1 of #ahcc1 tom4 v4 pt4 #a4 p4 #afj4 ,footnote #cc3 ,speaking of this tooth1 ,cuvier observes1 8,je l'avois cru d'abord ncessairement de paresseux2 mais aujourdhui que je connois mieux l'ostologie des divers tatous1 je trouve qu'elle ressemble au moins autant une dent de l'un des grands tatous40--,loc4 cit4 p4 #agb4 ,footnote #cd3 ,synopsis ,mammalium4 ,footnote #ce3 ,it is most probable that the substance which is here termed 8enamel10 is similar to that which forms the dense prominent ridges in the tooth of the ,megatherium1 and which ,i have shown to be composed of minute parallel calcigerous tubes1 similar to the ivory or bone of the human tooth4 ,footnote #cf3 ,medical and ,physical ,researches1 pp4 #cbc-d4 ,footnote #cg3 ,loc cit4 p4 #ccj4 ,footnote #ch3 ,spix and ,martius1 ,reise in ,brazil1 ,band ii4 p4 #e4 ,footnote #ci3 ,harlan's ,medical and ,physical ,researches1 #ahce1 p4 #ccd4 ,m4 de ,blainville speaks of a cast of a fragment of a lower jaw 8portant encore cinq dents en srie20 as having been transmitted to the ,museum of the ,garden of ,plants from ,north ,america1 together with other bones1 all of which he refers to the genus ,megalonyx2 ,m4 de ,blainville does not describe these teeth1 which is to be regretted1 inasmuch as1 if he be correct in regard to their number1 which can hardly be doubted1 and if he wrote with any clear and definite ideas of the generic characters of ,megalonyx1 this would indicate that ,megalonyx differed generically both from ,megatherium and ,mylodon in a more important dental character than has hitherto been suspected 7,see 8,comptes ,rendus1 c40 #ahci1 ,no4 ,v4 p4 #adb47 ,footnote #dj3 ,dr4 ,harlan also indicates differences in certain parts of the skeleton of the ,new ,york fossils as compared with his ,megx4 laqueatus2 but thinks them probably due to a difference in the age of the individuals3 he says 8,there is also in ,mr4 ,graves' collection1 in ,new ,york1 a tibia1 nearly perfect from the right leg2 the segment of a flattened sphere1 on which the external condyle of the femur moves1 is rather more depressed1 than in the specimen from ,big-bone-cave4 ,other marks and peculiarities are observable on this bone1 not found on that of the ,megalonyx laqueatus of ,big-bone-cave1 but they are probably due to a difference in the age of the individuals40 ,loc4 cit4 p4 #cce4 ,footnote #da3 1 mola2 1 dens4 ,footnote #db3 ,if the lower jaw of ,mylodon ,harlani1 bears the same proportion to its teeth as does that of ,mylodon ,darwinii1 it must be about two feet in length4 ,footnote #dc3 ,see ,proceedings of the ,geological ,society1 ,march #ahci1 and ,parish's ,buenos ,ayres1 p4 #agh1 b1 ,pl4 #a1 fig4 #b and #c4 ,footnote #dd3 1 femur2 1 bellua2 in allusion to the disproportionate size of the thigh-bone4 ,footnote #de3 ,this beach is covered at spring tides2 many parts of the skeleton were encrusted with recent ,flustr1 and small marine shells were lodged in the crevices between the bones4 ,footnote #df3 ,it requires little stretch of imagination to conceive that this more complex posterior tooth 7,pl4 ,,xxiii41 fig4 #d1 #d7 in the lower jaw is the representative of the two smaller posterior teeth 7ib4 fig4 #c1 #d1 and #e7 of the upper jaw conjoined4 ,footnote #dg3 ,lund1 ,videnskabernes ,selskabs1 ,natur43 og ,mathem4 ,afhandlinger1 ,kibenhavn1 vol4 viii4 ,footnote #dh3 ,linn4 ,trans4 vol4 xvii4 7#ahcc7 p4 #ag4 ,footnote #di3 ,zool4 ,proceedings1 #ahcb1 p4 #acd4 ,footnote #ej3 ,the anterior prolongation of the sternum in front of the neck and the corresponding anterior position of the clavicles and scapul occasions a transference of such a proportion of the moving powers of the head from the cervical vertebr to these bones in the mole1 as renders any modifications of these vertebr1 like those in the ,armadillo1 uncalled for4 ,footnote #ea3 ,loc4 cit4 ,footnote #eb3 ,bridgewater ,treatise1 p4 #df4 ,footnote #ec3 ,bridgewater ,treatise1 p4 #aeb4 ,footnote #ed3 ,dasypus #f-;cinctus1 ,l41 is the species of which ,i have the astragalus separate1 so as to be able to follow out the comparison4 ,footnote #ee3 ,in distinguishing these trochle as fibular and tibial1 it is to be understood that the terms relate only to aspects corresponding to the position of those bones1 and not that the fibula is articulated to the whole of the trochlea so called3 it probably rested only upon the outer facet in the ,scelidothere4 ,footnote #ef3 ,this astragalus was found at ,santa ,f1 in ,entre ,rios1 associated with the remains of the ,mastodon and ,toxodon2 but from its size and form ,i entertain little doubt that it belonged to a ,megatherioid quadruped as large as the ,mylodon or ,megalonyx4 ,the brief allusion to the astragalus of the ,megalonyx in ,m4 ,lund's ,memoir does not afford the means of determining with certainty this point4 ,footnote #eg3 ,see the figures of this bone1 given by ,cuvier in ,pl4 x4 and xi4 ,ossemens ,fossiles1 vol4 v4 part i4 ,footnote #eh3 ,ossemens ,fossiles1 vol4 v4 part i4 p4 #afc4 ,footnote #ei3 ,for the translation of the following passage1 and of others alluded to in the present work1 from the original ,danish ,memoir of ,m4 ,lund1 loc4 cit41 ,i am much indebted to the ,rev4 ,w4 ,bilton1 ,m4,a4 c4 c43-- 8,thus in every point of comparison we have instituted between the organization of burrowers and climbers2 we have seen that the ,megalonyx constantly differs from the former and resembles the latter2 but the point to which ,i last alluded 7the obliquity of foot71 ,i consider to be quite decisive4 8,there is one other point in its organization1 which is not quite without weight in reference to our present inquiry1--,i mean its unusually powerful tail4 ,now1 it is certainly true that many animals which are not climbers have a powerful tail1 as e4 g4 ,armadillos1 while the others that climb well1 have none1 as ,sloths and ,apes4 ,but when we find a remarkably powerful tail attached to an animal that according to all probability was a climber1 we are led to infer that this organ must have served for that purpose3 in other words1 that the ,megalonyx was furnished with a prehensile tail4 8,how far the ,megatherium is to be considered in the same light as the ,megalonyx cannot be decided without an accurate and scientific examination of its skeleton at ,madrid4 ,pander and ,d',alton do not mention any distortion of the hind-foot1 neither does their figure exhibit any4 ,it is nevertheless quite possible that such may exist1 but that it is disguised by the faulty manner in which the skeleton is put up4 ,it strikes me as little probable that two animals which agree so well in the principal particulars of their organization should differ so much in one of the most important4 ,the ,megatherium has been proved by later discoveries to possess the same powerful tail as the ,megalonyx1 and as it corresponds also with the latter entirely in the conformation of its extremities1 the same difficulties present themselves against the supposition of its having been a burrower4 ,but if the ,megatherium was really a climber1 it must have had still more occasion 7on account of its greater size71 for that peculiar arrangement of the hind-feet which we have described in the ,megalonyx40 ,footnote #fj3 ,descripcion del ,esqueleto de un quadrupedo muy corpulento y raro1 que se conserva en el ,real ,gabinete de ,historia ,natural de ,madrid4 ,folio1 ,madrid1 #agif4 ,footnote #fa3 ,ossemens ,fossiles1 tom4 v4 pt4 i4 p4 #agi4 ,footnote #fb3 8,das ,riesen ,faulthier1 ,bradypus giganteus1 von ,dr4 ,chr4 ,pander und ,dr4 ,e4 ,d',alton40 ,folio1 ,bonn1 #ahba4 ,footnote #fc3 ,transactions of the ,geological ,society1 #ahce1 p4 #dch4 ,footnote #fd3 ,an excellent translation of the description of the ,brazilian fossils found by ,m4 ,lund1 is published in the ,annals of ,natural ,history1 ,july and ,august1 #ahci4 ,footnote #fe3 ,at the distance of a few leagues from the locality here mentioned1 other fragments were found by ,mr4 ,darwin2 also near ,santa ,f1 in ,entre ,rios2 also on the shores of the ,laguna1 near the ,guardia del ,monte1 ,south of ,buenos ,ayres2 also1 according to the ,jesuit ,falkner1 on the banks of the ,tercero4 ,footnote #ff3 ,mr4 ,darwin has more particularly described the circumstances of the embedment of this tooth in his ,journal of ,researches1 p4 #adi1 during the ,voyage of the ,beagle4 ---------------------------------------- -------------------------------- ,,transcriber',s ,,notes #a4 ,the ,errata was corrected4 #b4 ,silently corrected obvious typographical errors and variations in spelling4 #c4 ,retained archaic1 non-standard1 and uncertain spellings as printed4 #d4 ,re-indexed footnotes using numbers and collected together at the end of the last chapter4 #e4 ,enclosed italics font in underscores4 #f4 ,denoted superscripts by a caret before a single superscript character1 e4g4 ,mr4