6a THE PHYSICAL KINSHIP 



the lowest catarhine to the most highly developed 

 man.' Associated with this fossil ape-man were 

 the fossils of the elephant, hyena, and hippo- 

 potamus, none of which any longer exist in that 

 part of the world, also the fossil remains of two 

 orders of animals now extinct. The genealogy of 

 the crocodile has been traced by Huxley, through 

 all intermediate stages, back to the giant reptiles 

 of the early Tertiary.* And the pedigree of the 

 horse has been even more completely worked out 

 by the indefatigable Marsh. In the museum of 

 Yale University may be seen the fossil history of 

 this splendid ungulate, from the time it was a 

 clumsy little quadruped only 14 inches high, and 

 with four or five toes on each foot, down to existing 

 horses. The earliest known ancestor of the horse, 

 the eohippus, lived at the beginning of the Eocene 

 epoch. It had five toes, almost equal, on each 

 front foot (four toes behind), and was about the 

 size of a fox. The orohippus, which lived a little 

 later, had four toes on each front- foot, and three 

 behind. The mesohippus, found in the Miocene, 

 had three toes and one rudimentary toe on each 

 front-foot, and three toes behind. It was about 

 the size of a sheep. The miohippus, which is 

 found later, had three toes on each of its four feet, 

 with the middle toe on each foot larger than the 

 other two. The pliohippus, living in the Pliocene 

 epoch, had one principal toe on each foot, and two 

 secondary toes, the two secondary toes not reach- 

 ing to the ground. It was about the size of a 

 * See table of geological ages, p. 79. 



