THE EVOLUTION OF THE HORSE 



many breeds), the wild horses of Mongoha, the half asses 

 (the kiang and the onager), the asses, and the zebras. The 

 genus includes eight to twenty species of living animals, the 

 number discriminated depending upon the judgment or the 

 fancy of the naturalist making the classification. Most of 

 the later fossil horses are so nearly like the living horses that 

 they have all been placed in the genus Equus. Any one who 

 sees restorations of these animals at once calls them horses, 

 zebras, asses, though some are much smaller than the living 

 animals of these kinds. 



North America was an early home of the horse, whose 

 remains have been found in deposits in Wyoming that were 

 laid down in Eocene time. (See the geological table.) At 

 that time the climate of North America was warmer than it 

 is now and Alaska was linked to Asia by land over which 

 horses migrated. The Eocene lignite beds and gypsum 

 deposits of France contain abundant bones of horses, and 

 bones are found also in England, which was then connected 

 with the Continent. 



The earliest horses whose remains are found in America 

 are the Eocene forms known as Eohippus (the "dawn 

 horse"), some of which stood only about a foot high at 

 the shoulder. The fore foot had four toes, the hind foot 

 three toes, but each showed a vestige of an additional toe. 

 The teeth were simple and short. Three kinds of Eocene 

 horses have been distinguished, called Eohippus, Orohippus, 

 and Epihippus. These horsed appear to have lived in West- 

 ern North America and in England at nearly the same time. 

 Some of them appear to have inhabited either park-like open- 

 ings in forests or the forests themselves. 



By the end of Eocene time or a little later all the European 

 horses seem to have disappeared, for the deposits laid down 

 in Europe about that time contain no bones of horses. In 



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