EVOLUTION OF THE HORSE . 5 



and these are just beginning to show signs of fusing into 1 n 



ts. The premolar teeth have only one main cusp, except the 

 third and fourth premolars (next the molars) in each jaw, which 

 have two and three, respectively. The only specimens which 

 have been found were in the London Clay or Lower Eocene of 

 England and are preserved in the British Museum. 



The Eohippus is much better known. It eomes from the Lower 

 ene ^i Wyoming and New Mexico, and is very like the lly- 



<S> s ^ 



FIG. 1.— UPPER AND LOWER TEETH OF EOHIPPUS," FROM 

 THE LOWER EOCENE OF WYOMING. NATURAL SIZE 



racotherium except that the molar teeth have the cusps more 

 clearly fusing into cross-erests, and the last premolar is begin- 

 ning to look like one of the true molars. The forefoot of this 

 animal has four complete toes and the splint of a fifth. The 

 hindfoot has three complete toes and the splint of another. A 

 •men of the hindfoot is shown in the series in the A-case and 

 many incomplete specimens, skulls, jaws etc., of several sp 

 in the count 



3 and 4. Protorohippus and Orohippus. MIDDLE BOCBNB. 

 In these animals the splint of the first digit in the forefoot and 

 the splint of the fifth digit of the hindfoot have disappeared, but 

 ther il] four complete toes in tin* fore- and three in the hind- 



The lolars are a little clearer and the last 



premolar has become almost like the molars, while the next t<» 

 the last premolar is beginning t<» become so. A skeleton of 



:ippus is mounted in the wall-case-. It shows an animal 



if a small dog, and propoii inch like the breed 



known as the whippet, of which a skeleton has been placed nearby 

 for comparison with the Protorohippus skeleton. T 



hippus imd by Dr. I. L. Wortmarj in iHSo in the Wind 



