264 THE ANIMALS AND MAN 



wild ancestors, namely Equus przewalskii of northern Asia, 

 from which all the Oriental, Mongolian, Arabian, North 

 African and East European races have sprung; and 

 Equus caballus fossilis, or the diluvial horse, of Europe, from 

 which the German, Norman, English and West European 

 horses generally have arisen. In America fossil horses have 



FIG. 138. Arion, a record-holding American trotting horse. (After 

 Plumb.) 



been found back through a series of geologic ages as far as 

 the beginning of the Tertiary age forming a connected series 

 from the small Eohippus of the Lower Eocene period, about 

 the size of a fox, and with four toes and splint of the first digit 

 on the front feet and three toes and splint of the fifth di- 

 git on each hind foot; through Protorohippus and Oro- 

 hippus of the Middle Eocene, about 14 inches high, with 

 four toes on front feet and three toes on hind feet, and no 

 splints; through Mesohippus of the Oligocene, about the 



