THE EOCENE OF EUROPE AND NORTH AMERICA 



155 



polyprotodont marsupials in this country. Among the Carnivora-Creo- 

 donta, we find three famihes, the oxyienids, hysenodontids, and mesonychids, 

 the last developing into animals of formidable size. 



The Insectivora are highly varied, including six families, four of which 

 are now extinct, while two are doubtfully compared with the modern 

 moles (Talpidae) and tenrecs (Centetidae) as well as with the tupaiids or 



Fig. 5G. — Skeleton of U uitdthcriuin {mirahilc), the timljlypod successor of Pantolambda 

 and Coryphodon. Uintatherium Zone, Upper Bridger. (See Fig. 58.) In the American 

 Museum of Natural History. After Osborn. 



tree shrews. The peculiar herbivorous Tillodontia apparently become ex- 

 tinct in Tilhlherium of the Bridger. The archaic edentates with enameled 

 teeth (Taeniodonta) survive into the Lower Bridger only {Stylinodon). 

 Of the archaic Ungulata the phenacodonts have all disappeared, but the 

 ambly]wd stock is apparently flourishing and reappears in the imposing 

 Uintatherium of the Middle Bridger. In the Middle Eocene the ratio of 

 archaic and modernized genera and species of mammals is as follows: 



Archaic mammals 

 Modernized mammals 



Thus there is for the first time a decided predominance of the modern- 

 ized over the archaic forms. Among what we have been regarding as the 

 more modern types, the arboreal primates now include two families (Anap- 



