142 



THE AGE OF MAMMALS 



Fig. 49. — Heads of American Upper 

 Eocene mammals not thus far known in 

 western Europe. * Outline restorations 

 by Charles R. Knight. A. Eohasileus, 

 an amblypod. B. Protitanotherium, a 

 titanothere. C. Dolichorhinus, a titano- 

 there. D. Manteoceras, a titanothere. 

 E. Harpagolestes, a creodont. Chiefly of 

 Upper Washakie Age, Eobasileus Zone. 



* It is possible that the family of titanotheres 

 may have existed in eastern Europe at this time. 



Increasing separation from America. 

 — Riitimeyer 1 attempted to draw many 

 parallels between the Middle Eocene 

 mammals of Switzerland (Egerkingen) 

 and those of the Rocky Momitain 

 region, but all recent research (Osborn, 

 Matthew, Stehlin) ^ has tended to 

 separate these animals more and more 

 widely. To begin with, the odd-toed 

 imgulates (perissodactyls) of the two 

 countries are quite different. The 

 horses, which evolved in great abun- 

 dance and variety in France, can only 

 be broadly compared with those of the 

 Rocky Mountains. The palseotheres 

 of France, three-toed animals near of 

 kin to the horses, never reached Amer- 

 ica at all. The lophiodonts, it is true, 

 are represented in both countries, but 

 by dissimilar forms. Of even-toed 

 mammals, the European dichobunes 

 may have some relationship with the 

 American homacodonts. Of all the 

 remaining even-toed or artiodactyl 

 mammals, which appear in such pro- 

 fusion in France, no counterparts what- 

 ever are found in America. This is 

 true as well of the carnivores and other 

 unguiculates; the so-called Calamodon, 



' Riitimeyer, Die Eocane Saugethier-Wclt 

 von Egerkingen. Abhandl. schweiz. paldont. 

 GeselL, Vol. XVIII, Zurich, 1861. 



2 See Bibliography. 



