EVOLUTION OF THE HORSE 



19 



while in the Upper Oligocene occurs Mesohippus intermedins as 

 large as a sheep. Of both these animals all parts of the skeleton 

 are known, and a good series of skulls, feet, jaws, palates etc. is 



FIG. 2.— UPPER AND LOWER TEETH OF "MESOHIPPUS BAIRDI," 

 FROM THE MIDDLE OLIGOCENE OF SOUTH DAKOTA. NATURAL SIZE 



exhibited in the counter-case, besides the specimens shown in the 

 series of feet and in the series of skulls. 



8. Anchitherium. Lower Miocene. This stage has been 

 found both in Europe and in America. It is much like its prede- 

 cessor, but is larger and has the crests of the teeth somewhat 

 higher and more complete. It probably is not in the direct line of 

 descent of the horses, but is on a side branch. A palate, jaws, 

 teeth and foot-bones are exhibited here. 



9. Parahippus and Hypohippus. Middle Miocene. In Par- 

 ahippns the tooth-crests are much higher, and the transverse 

 ridges on the upper molars are beginning to change shape so as to 

 become a second pair of crescents inside the outer pair. Hypo- 

 hippus is off the direct line of descent ; its teeth are like those of 

 Anchitherium, by which name it has been generally called, but 

 the animal was much larger, equalling a Shetland pony in size. A 

 complete skeleton of the Hypohippus is shown in wall-case 15, 

 and illustrates very well the general characters of the Three-Toed 

 Horses, although it is not in the direct line. This specimen was 

 found near Pawnee Buttes, Colorado, in 1901 by Bamum Brown, 

 of the Whitney expedition. Other incomplete specimens of 

 Hypohippus, Parahippus and Merychippus are shown in the 

 counter-case, and casts of the feet and skull in the evolution se- 

 ries in A-Case 49. It may be observed that in the forefoot of 



