396 LAND MAMMALS IN THE WESTERN HEMISPHERE 



slender limbs and feet. The teeth were present in undiminished 

 number, 44 in all ; the lower incisors were small, simple, nearly 

 erect and chisel-shaped, very different from the large, pro- 

 cumbent and shovel-like teeth of the modern genera, and the 

 trenchant canines were much smaller than in the latter. The 

 first premolar had an isolated position, the second and third 

 were trenchant and much extended antero-posteriorly, quite 

 as in many other groups of primitive artiodactyls. The 

 molars, which were typically selenodont, were low-crowned in 

 the upper jaw, but in the lower showed an incipient tendency 

 to hypsodontism. The skull, by its shape and the characteris- 

 tic narrowing of the face, immediately suggests the modern 

 type, but differed in many details of structure, the most ob- 

 vious of which were the incompletely closed orbits, the shallow 

 and slender jaws, and the very large, hook-like process from the 

 angle of the lower jaw, which, in greatly reduced form, is pres- 

 ent in both of the Recent genera. The neck was relatively 

 long, though by no means so long proportionately as it sub- 

 sequently became, and the vertebrae had already acquired the 

 peculiarity found in all the succeeding camels, of the exceptional 

 position of the canal for the vertebral artery, save in the sixth 

 vertebra, where it pierced the transverse process, as in mam- 

 mals generally ; the odontoid process of the axis was neither 

 spout-like nor peg-like, but of intermediate form, convex 

 below and fiat above. The body was long and light, and the 

 ribs were much more slender than in the Recent genera. The 

 fore and hind limbs, which were of nearly equal length, were 

 very slender ; the humerus had a single bicipital groove ; the 

 fore-arm bones were fully coossified and in the lower leg only 

 the two ends of the fibula remained. The feet were already in 

 the stage of development which persisted through the lower 

 Miocene in all of tlie phyla, with two separate digits and nodular 

 remnants of two others, and deer-like hoofs. 



It would be of interest to compare this little A^liite River 

 camel with its contemporary genus of horses, '\Mesohippus, 



