THE EOCENE OF EUROPE AND NORTH AMERICA 



167 



whole being less doliehocephalic. Another feature of tlie archaic fauna is 

 the giant size attained by members of the creodont mesonychids, the skulls 

 of which equal those of the large modern brown bears of Alaska. The 

 oxysenids are represented by much larger and more specialized forms of 

 Limnocijon than those from the Upper Bridger. 



In regard to the modernized fauna the most conspicuous fact is the first 

 appearance among the Pcrissodactyla of a new family of rhinoceroses, 

 destined to become amphibious ( Amynodontidis) . Among titanotheres 

 the extremely brachycephalic Palososyops, belonging to a phylum already 

 dwarfed (P. copei) in the lower stage, is now apparently extinct. The 



Fig. 67. — Heart of the Washakie Badlands in the Eobasileiis Zone, "Adobe Town," five 

 miles east of I^nney Ranch, Wyoming. Photograph by American Museum of Natural 

 History, 1895. 



most signal advance in this titanothere family is the appearance of the 

 extremely long-headed Dolichorhinus (Fig. 49) with incipient horns, an 

 extreme type also destined to become extinct, while the less extreme propliet- 

 horned titanothere Manteoceras (Fig. 49) apparently survives and gives 

 rise to certain of the giant quadrupeds of the Lower Oligocene. Among 

 Artiodactyla of the entelodont family the roliust 'giant pig' or omnivore 

 Achcenodon is also distinctive of this level. The other mammals represent 

 a continuation of the Bridger fauna. All the small mammals are com- 

 paratively rare, probal)ly because the coarse conditions of deposition were 

 unfavorable for their preservation. Thus the Equidse and the Artiodactyla 

 of this stage are still unknown. The mammals characteristic of this deposit 



