280 LAND MAMMALS IN THE WESTERN HEMISPHERE 



be positively identified, but most probably was Asia. From 

 the same region and at a corresponding period of time Europe 

 received many of the same forms, and so many genera were at 

 that time common to the latter continent and North America that 

 a broad and easy way of intermigration must have been open. 



One of these immigrant orders, the Rodentia, the most 

 ancient known members of which were these species from the 

 North American Wasatch, was represented by the same family 

 (flschyromyidse) and some of the same genera {-fParamys, 

 ■\Sciuravus) as throve also in the Bridger stage. 



There were two orders of hoofed mammals, which were 

 newcomers to the western world, Perissodactyla and Arti- 

 odactyla. Of the former was a genus {\Eohippus) of the most 

 ancient American horses. These most interesting little ani- 

 mals, no larger than small foxes and domestic cats, would 

 hardly be called horses, were it not for the long series of gradual 

 and successive modifications which led from ^Eohippus up 

 to the modern horses. The graceful little creatures had a short 

 neck, curved back, and relatively short, slender limbs, with 

 four functional toes in the front foot and three in the hind ; and, 

 though they differed from existing horses in almost every detail 

 of teeth and skeleton, there was something unmistakably equine 

 about them. From the abundance of their remains it may be 

 inferred that herds of them swarmed in the forests and glades 

 of Wasatch times. The second perissodactyl family, the 

 fLophiodontidse, which comprised considerably larger animals, 

 never attained to importance in America, but flourished and 

 became greatly diversified in Europe. What are believed to 

 be the most ancient tapirs yet discovered {^Systemodon) were 

 individually very common in the Wasatch. This tapir was no 

 larger than a Coyote, had no proboscis and was so little like 

 a tapir in outward appearance that an observer might well 

 be pardoned for overlooking the relationship ; e^^en the skel- 

 eton is of so indifferent a character that the reference of this 

 genus to the tapirs cannot be positively made. 



