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Show 42 ZOOLOGY OF TilE VOYAGE OF THE BEAGJ,E. . 1 f t turned towards and nearly con( fig. 4, Pl. VIII.) have concav~ artteu ar ta.ce ~t'es. so as to 'form together a . . l . t their lower ex reml l ' ~ tmued mto, each ot lei. a . h the corresponding convex articular snrfaces deep semilunar notch, mto wine d' . . . ei·tebra (fig 3 Pl. VIII.) are . · . s of the a JOmmg v · ' of the poster1or oblique piOcesse . . f tl e two anterior concave articular d I tl 1 se approxnnatwn o 1 firmly locke . n 1e c 0 · . t 1 ' from· eac 1 th . nly by a vertical ridge, and a 1 o er 0 < facets, whtch are sepma ec i' 1 . . br·eadth the lumbar vertebrm f b t tl ·ee or 10ur mes m ' rough surface o a ou 11 f 1 H . and differ from those of h ble those o t 1e Oise, ' of the Macrauc ene rese~ . 11 · in which those surfaces are wider the Camel-tribe and Rummants genera y, ·f l . ·ocesses the lumbar apart. In the hook-like f~rm, h~-~e~e~~r~: tl;~~:c a~;c~h:I ~~rse ; and resemble vertebrre of the Macrauc lene .~ er 1 ·here ·* but the degree those of many Ruminant spectes, and of the Anop ~t 'M . h It of concavity of the articulatm. g sunr.a ce · t 0 O'reat m the acrauc ene. IS no s o < b f th would b~ interesting to determine the relations which the_lm~ba~· verte. rre 0 . ~ Macrauchene bear to those of the Palreothere; but the mcltc~twn w.lnch Cuvie: gives of the single lumbar vertebra, of which he had c~gmzance m the latte o·enus'! is too slight to enable me to enter upon the companson. . The whole length of the lumbar region in the Macrauchene IS twenty · 1 When the bodies of these vertebrre are naturally adapted together, me 1es. . M 1 ere they form a sliO'ht curve, indicating that the loms of the acrauc 1ene w arched or bent 0 downwards towards the sacrnm. That the h~mbar vertebrre were rigidly connected together, or but slightly flexible, is evident fro~ the flatness of the articular surfaces of the vertebral body, and by th~ Circumstance of ossification having extended along the anterior vertebral ligaments, and produced an anchylosis between the fourth and fift~ lumbar vertebrre; (fi g. 2 ' C' PI . VIII.) This kind of ossification is frequent m aged horbse s, abn d I have seen an example of a similar anchylosis of the lumbar verte rre, . Y abnormal deposition of bone in their anterior ligaments, in the skeleton of a Hippopotamus preserved in the Senkenbergian Museum, at Frankfort. . In preparino· the preceding account of the cervical and lumbar regwns.of the vertebral col:mn of the Macrauchene, I have felt frequently a strong desue to enter into a comparison between them and the corresponding vertebrre of ~he extinct Pachyderms of the Paris Basin. Some of these, as the Anoplotlterzum gracile, in the length and slenderness of the cervical vertebrre, resemble both Auclteuia and jJfacraucltenia; others, as the Palceotlteriwn minus, and probably the rest of the genus, resemble the Camelidce and JJfacraucltenia in having seven lumbar vertebrre. Cuvier points out the resemblance which the atlas of the Anoplothere bears to that of the Camel, and especially of the Llama ;i: but he * Cuvier, Ossemens Fossiles, iii. p. 238. t Loc. cit. p. 234. t Loc. cit. p. 235. FOSSIL MAMMALIA. 43 expressly notices the existence of the canals for the vertebral artery in the fifth or sixth cervical vertebra of the Auoplotlteriwn commuJte.* Do the cervical vertebrre- say fi·om the third to the sixth inc1usive-of the Palceotlterimn pre.·ent an imperforate condition of their transverse processes, or exterior part of their sides? Cuvier, who seems not to have been aware of this peculiarity in the Came/idee, merely notices the absence of these arterial foramina in the last cervical vertebra of the Patceot!terium minus,'j" which, unfortunately for the comparison I am desirous of establishing, is that which most commouly presents this imperforate condition in the Mammalia generally. As, however, the cervical vertebrm of the Palreothere had the anterior articular surface of the body convex, and the transverse processes produced into descending laminre, it is most probable that they corresponded with the cervical vertebrre of the typical Pachyderms in the condition of their arterial foramina. The sacrum and ossa innominata in the present specimen of .JJ-Iacraucltenia are very imperfect; but sufficient is preserved to show that the sacrum was anchylosed to the ilia: the lower boundary of this anchylo is is marked bClow by an external ridge, and by vascular canals and grooves in the substance of the bone, as in the Hippopotamus. The body of the sacrum is lost, but tlle smooth articular convexities upon the transverse processes adapteu to the articular depressions of the last ]urn bar vertebra are fortunately preserveu. The remains of the anterior extremity of our Macrauchenia include fragments of a left scapula; the proximal extremities of the anchylosed bon s of the right antibrachi urn ; the metacarpal and most of the phalangeal bones of the riO'ht fore-foot. The iirst-mentioneu fragments, include the head and neck of the scapula, a small part of its body with the beginning of the spine, the coracoid process, and the nearly entire glenoid cavity. This articular surface (fig. 2, Pl. IX.) resembles in its general form, and degree of concavity, that of the Camel and Rhinoceros, and is deeper than in the Hippopotamus. The coracoid process is represented by a slightly produced rough, thick, anu oLtuse tuberosity, situated closer to the glenoid cavity than in the Camelidce or Rhinoceros, and having almost the ame relative position and size, as in the Patceot!terium crassum. The superior border or costa of the scapula presents much ·variety in the Ungulate quadrupeds with which we have to compare the l\Iacrauchenia. In the Ruminants its contour forms behind the coracoid a coucave sweep, which auvanccs close to the spine of the scapula. In the Camel and Ilor e the marginal concavity is shallower, and the distance of the superior costa from the spine of the scapula is greater; the extent of the supra-spinal fossa increases in the true Pachyderms, and the Macrauchene agrees with them in this structure. In the Tapir, how- * Loc. cit. p. 237. t Loc. cit. p. 232. |