434 



GENERAL ZOOLOGY 



ancestors of the species of today, for no species of mammal 

 which was in existence in the Age of Mammals has lasted 

 through to the present time. 



Of few other animals have we so complete and satis- 

 factory a geological record as of the horse. From fossil 

 remains found in the western part of the United States we 



Fig. 227. Reconstruction of an early fossil horse (Eohippus) 

 American Museum of Natural History 



are able to trace its evolution from an ancestor (Eohip'pus, 

 Fig. 227) a little larger than a cat, with four toes on the 

 front feet and three on the hind feet. The figure of Eohip- 

 pus is photographed from a water color by Mr. Charles 

 R. Knight, based on skeletal material at the American 

 Museum of Natural History. The markings are drawn as 

 they are supposed to have existed on the animal. There is 

 reason to believe that the undiscovered ancestors of this 

 early form had five toes on each foot. The transition to the 



