FOSSIL VERTEBRATES— MAMMALIA I 73 



of the lakes or streams and gathered together in great herds. 

 The time of their greatest development was the Oligocene, and 

 in the beds of the White River deposits the remains are found 

 in the greatest abundance. 



Protoreodo7i . — Uinta. 



Agrioclwerus. — White River, a peculiar form that had the 

 toes terminated in sharp claws like the Sloths. 



Oreodon. — White River. 



Lcptanclicnia and Cyclopedias. — Upper Miocene, Deep River. 



Camelidae .— The camels seem to have developed first on the 

 North American continent in the Middle Eocene, Uinta, and 

 Bridger, and to have died out in the Pliocene. They are pecu- 

 liar in the much elongated head and the deficient anterior den- 

 tition. In the older forms the metapodials are separate as in 

 the families already described, but in the later ones the two are 

 joined and only a thin layer of bone separates the two medullary 

 cavities. 



In South America during the Pliocene time there were devel- 

 oped a large number of forms that became extinct, with the 

 exception of the existing Llama. The genus Camelus appeared 

 in Asia in the Lower Pliocene without known forerunners, and in 

 North Africa at the beginning of the Pliocene. 



Leptotragulas . — U n i t a . 



Poebrotherium. — White River. 



Protolabis. — Loup Fork. 



Procame/us. — Loup Fork. 



Anoplotheridae . — Small extinct forms that were developed in 

 the Eocene of Europe and died out in the lower Miocene. 

 They seem never to have extended beyond the limits of the 

 continent of Europe. They were among the first to develop the 

 selenodont form of teeth that is the characteristic form of the 

 deers and the most of the ruminants. 



A no plotl i erium . — Eocene. 



Diclwbune. — Eocene. 



Xiplwdon . — Eocene. 



Ccenotherium.— Miocene. 



