534: 



CENOZOIC ERA— AGE OF MAMMALS. 



ants. Their feet were provided each with five toes (Fig. 911), and the 

 brain was proportionally smaller than in any other land mammal. 



Another extraordinary group of animals discovered by Marsh in the 

 Eocene beds has been placed by him in a new order called Tillodontia 

 (Fig. 914). These animals combine the head and claws of a bear with 

 the incisors of a Rodent and the general characters of Ungulates. The 

 order must be regarded, therefore, as a remarkable generalized type. 



We have seen the earliest in the line of descent of the horse family 

 — Eoliippus — in the Lower Eocene Wahsatch beds. In the Middle 



Fig. 913.— Limnohyus (Palaeosyops) (after Leidy). 



Eocene Bridger beds we find the next in the series — the Orohippus 

 (mountain-horse). This was of similar size; but already the fifth 



Fig. 914.— Eocene Mammal: Skull of Tillodontia (after Marsh). 



metacarp and rudimentary toe are gone, and there were now three 

 hoofed toes on the hind-feet and four functional toes on the fore-feet. 



