THE PREHISTORIC HORSE 



represented by splints on fore and hind foot. On the fore foot 

 no trace remains of the little nodules which in Protohippus rep- 

 resented the first and fifth toes. The crowns of the teeth are 

 much longer and the teeth have changed otherwise. The skull 

 has lengthened and the horse is much larger. 



Tracing the development of this prehistoric horse, we find 

 that the animal gradually increases in height, the number of toes 

 reduces to one on each foot, while the teeth increase in length 



Head 



Fore Foot 



HindFoot 



Teeth 



OneToe. 



Splints of 



2nd and 4th 



digits 



OneToe 



Splints of 



2nd and 4th 



digits 



Protohippus 



Mesohippus 



Protorohippus 



ThreeToes 



Side toes 



not touching 



the ground 



ThreeToes 



Side toes 



not touching 



the ground 



Long- 

 Crowned, 

 Cement- 

 covered 



ej ThreeToes 

 1 1 Side toes 

 Aft touching the 



ground; 

 Splint of 5th digit 



ThreeToes 



Side toes 



touching the 



ground 



Four Toes 



Short- 

 Crowned, 

 without 

 Cement 



Hyracotherium 

 (EohippusJ 



FourToes 

 Splint of 

 1st digit 



ThreeToes 

 Splint of 

 5th digit 



FIG. 2. Comparative drawings of skulls, feet, and teeth of prehistoric horse, 

 showing evolutionary development. Reproduced by permission from 

 Guide Leaflet No. 9, American Museum of Natural History 



and crown development. The tooth of the modern horse may be 

 an efficient grinder for twenty-five or thirty years, while that of 

 the prehistoric one, from shortness of crown and lack of enamel 

 and dentine, perhaps would not serve over ten or twelve years. 



The color of the prehistoric horse is not known, but it is sup- 

 posed to have been more or less striped, like the zebra, though 

 not brilliantly colored. The groundwork of this color was pre- 

 sumably dun or khaki. 



