FOSSIL MAMMALIA. 



4.) 



expressly notices the existence of the canals for the vertebral artery in the fifth 

 or sixth cervical vertebra of the Anoplotherium commune.* Do the cervical ver- 

 tebra— say from the third to the sixth inclusive — of the Palceotherium present 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 Camelidcs, 

 merely notices the absence of these arterial foramina in the last cervical vertebra 

 of the Palceotherium minus,\ which, unfortunately for the comparison I am de- 

 sirous of establishing, is that which most commonly presents this imperforate 

 condition in the Mammalia generally. As, however, the cervical vertebrte of the 

 Palaeothere had the anterior articular surface of the body convex, and the trans- 

 verse processes produced into descending laminae, it is most probable that they 

 corresponded with the cervical vertebrae of the typical Pachyderms in the condition 

 of their arterial foramina. 



The sacrum and ossa innominata in the present specimen of Macrauchenia 

 are very imperfect ; but sufficient is preserved to show that the sacrum was an- 

 chylosed to the ilia : the lower boundary of this anchylosis is marked below 

 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 the 

 smooth articular convexities upon the transverse processes adapted to the articular 

 depressions of the last lumbar vertebra are fortunately preserved. 



The remains of the anterior extremity of our Macrauchenia include frag- 

 ments of a left scapula ; the proximal extremities of the anchylosed bones of the 

 right antibrachium ; the metacarpal and most of the phalangeal bones of the right 

 fore-foot. The first-mentioned 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, PI. 

 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 pro- 

 cess is represented by a slightly produced rough, thick, and obtuse tuberosity, 

 situated closer to the glenoid cavity than in the Camelidcs or Rhinoceros, and 

 having almost the same relative position and size, as in the Palceotherium crassum. 

 The superior border or costa of the scapula presents much variety in the Un- 

 gulate quadrupeds with which we have to compare the Macrauchenia. In the 

 Ruminants its contour forms behind the coracoid a concave sweep, which ad- 

 vances close to the spine of the scapula. In the (Camel and Horse 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 Pachy- 

 derms, and the Macrauchene agrees with them in this structure. In the Tapir, how- 



Loc. cit. p. 237. 



t Loc. cit. p. 232. 



