388 LAND MAMMALS IN THE WESTERN HEMISPHERE 



are confined to the posterior side, not visible from the front. 

 The ungual phalanges are small and nodular, and the hoofs, 

 which carry no part of the weight, are hardly more than nails. 

 Under the other phalanges is a broad pad of elastic tissue, upon 

 which the weight rests, and the separation of the toes is very 

 partial. The peculiar external appearance of the camels is 

 largely due to structures which leave no trace in the skeleton, 

 and especially to the great humps, one or two according to the 

 species, which are accumulations of fat ; the ears are short 

 and rounded and the hair is not woolly, but almost straight. 



The teeth and skeleton of the llamas {Lama) are closely 

 similar to those of the camels, but the absence of humps, the 

 long, pointed ears, the woolly hair and the much smaller size 

 and lighter build give to the living animals a more marked 

 difference of appearance from the camels than one would expect 

 from a comparison of the skeletons alone. The dental formula 

 is : ^ §, c Y, p I, m f . The remaining upper incisor, the third, is 

 recurved, as is also the canine, but the spike-shaped first pre- 

 molar of the camels is absent and the other premolars are 

 much smaller than in the latter. In the skull the brain-case 

 is larger, and the sagittal and occipital crests are much less prom- 

 inent. The skeleton differs hardly at all from that of the 

 camels, except for its smaller size and more slender proportions. 

 The toes are more distinctly separated, each having its own 

 pad. Thus, among the existing representatives of the family 

 are two very well-defined phyla, each characteristic of a differ- 

 ent continent. 



The Blanco stage of the middle Pliocene, which has pre- 

 served but a meagre representation of the life of its time, has 

 yielded a number of very large, llama-like species, not, however, 

 ancestral to the modern species, for they had but one premolar 

 in each jaw. From the lower Pliocene we have fuller infor- 

 mation. In the Snake Creek stage the separation of the two 

 modern phyla was complete, and there was a third one, now ex- 

 tinct, that of the browsing or ' ' fgiraff e-camels " {\ Alticamelus) 



