List of Casts, Models, and Photographs. I 5 



during the Pleistocene. During the Tertiary the race evolved 

 from small deer-like animals, no larger than jack-rabbits, with 

 sharp, pointed hoofs and separate metapodial bones, to their 

 present size and proportions, the metapodials becoming solidly- 

 fused together and a large pad on the foot supporting the 

 weight of the body. Collateral lines of descent also existed, 

 one ending in an animal of singularly giraffe-like proportions, 

 although a true Camel (Giraffe-Camel, see also No. 10, on 

 page 5). 



Stage a. — Protylopus petersoni. Hind limb. No. 2564. Upper 

 Eocene (Uinta), Utah. Separate metapodials, lateral 

 digits represented by short splints, pointed hoofs. Size 

 of jack-rabbit. Price, $^. 



Staged. — Poebrotherium wilsoni. Fore and hind feet. No. 1364. 

 Lower Oligocene (White River), S. Dakota. Separate 

 metapodials, lateral digits represented by small nodular 

 rudiments, pointed hoofs. Size of vicuna. 



Price, ^5. 



Stages'. — Protolabis montanus. Fore and hind feet. No. 910S. 

 Middle Miocene (Loup Fork) , Colorado. Separate meta- 

 podials, lateral rudiments fused, hoofs pointed. Size of 

 llama. Price, $6. 



Stage/". — Alticamelus alius. (Giraffe-Camel.) Hind limb. No. 

 9109. Middle Miocene (Loup Fork), Colorado. United 

 metapodials, greatly elongated, hoofs considerably re- 

 duced. Size of small giraffe. Price, $12. 



33. Protoceras celer Marsh. 

 Fore and Hind Foot. 



Protoceras Beds, White River Oligocene, S. Dakota. 



Protoceras is the largest of a peculiar group of primitive 

 ruminants characteristic of the White River Oligocene. The 

 fore foot has four fully functional digits, but in the hind 

 foot the lateral digits are reduced to small splints. The 

 animal was somewhat smaller than the musk deer, much less 



