PALEONTOLOGY 



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comparatively short, and the orbit was placed well over the teeth, making 

 the face relatively short. 



1 



W 



1 



i 



I 



I 



/ 



I 



\ 



/ 



/ 



\ 



M 



W 



ID 



Fig. 221. — Diagrams of the feet of members of the horse series. The carpal and tarsal 

 bones are not separately represented. The Roman numerals indicate the numbers of dig- 

 its, the inner digit being designated I. A, fore and hind feet of Eohippus, lower Eocene; 

 B, fore and hind feet of Mesohippus, lower Oligocene; C, fore and hind feet of Merychippus, 

 Miocene; D, fore and hind feet of Pliohippus, Pliocene; E, fore and hind feet of Equus, 

 Pleistocene and recent. 



Mesohippus. — This animal was about 18 inches high. It had only 

 three digits on each foot, but on the outer side of the fore foot was a 

 splint bone representing an extra toe (the fifth). Figure 221 represents 



