I 70 STUDIES FOR STUDENTS 



ment of the limbs. There were forms with only a single digit 

 remaining, and others with three, resembling the Perissodactyls 

 in this character, but the same animals had the tarsus built on 

 the Artiodactyl plan so that they can belong to neither group. 



Thoathermm and Proterotherium are small animals from the 

 Santa Cruz formation of Patagonia. They were monodactyl, 

 the second and fourth digits being either completely lost or 

 greatly reduced in size. 



Macrauchenia was much larger than the other two, and resem- 

 bled the modern camel in size and some of the skeletal charac- 

 ters. The limbs were functionally tridactyl. The genus comes 

 from the Pleistocene deposits of Argentina. 



Amblypoda. — This suborder reached its greatest develop- 

 ment in the Eocene time and died out at the close of the same 

 period. The members of the suborder were all rather stout 

 animals that reached, near the time of their extinction, the size 

 of an elephant, or nearly so. The brain was very small and 

 almost devoid of convolutions ; there were five toes on each of 

 the feet, and the bones of the limbs were complete, i. e., the 

 tibia and the fibula, and the radius and ulna, were separate and 

 perfect. The group is generally divided into two families 

 according to the characters of the teeth, skull and limbs. 



Coryphodonlidae were animals limited to the lowest Eocene of 

 America, England and France. The greatest number and the 

 most perfect specimens have been obtained from the Wasatch 

 formation of the western part of the United States. 



Coryphodon, the typical genus, was a short and rather stout 

 animal about six feet long ; the skull was elongated in the facial 

 region with a rather broad muzzle armed with strong incisor 

 and canine teeth ; the feet were very short and strong with blunt 

 toes. The brain cavity was very small and limited to a small 

 part of the skull. The surface of the skull was without any bony 

 excrescences or with only very -faint ones. 



Di?wcerotidae : found in the Middle Eocene, Bridger ; animals 

 larger than the preceding family, and in general stouter and 

 stronger. The skull was longer and without the anterior 



