

THE NEW EVOLUTION 



which did not reach the ground, to larger ones which 

 reached the ground and must have borne some of the 

 weight of the animal in walking. A very few of the 

 horses of this period had feet like the modern horses — 

 that is, entirely without the lateral toes — but their 

 remains occur only in the later portion of the period. 

 Most of the horses of the earlier phases of the period 

 had longer and better developed lateral toes than those 

 of the middle and later phases. 



All horses with single toes, both modern and ex- 

 tinct, have on each foot a pair of long splint bones, one 

 on either side of the main toe, which in life are covered 

 by the skin. The upper ends of these bones are 

 greatly expanded and have well developed articular 

 facets for contact with the small bones of the wrists 

 or ankles. This part of the foot is identical in struc- 

 ture in the one-toed and in the three-toed horses, but 

 in the three-toed horses there are three additional 

 terminal bones on the lateral toes which are absent in 

 the one-toed horses. 



In the horses of the Pliocene and Miocene the 

 muzzle portion of the skull is usually relatively 

 shorter than in the modern horse, and the jaws are 

 not quite so deep, due to a difference in the relative 

 height of the crowns of the cheek teeth. In the 

 living horses and the horses of the Pleistocene or Ice 

 Age all the cheek teeth when fully formed have long 

 and nearly straight crowns from three to four inches 

 or more in height. These are set deeply in the jaws 

 and move outward as they are worn away by use. It 

 is this type of tooth which, as remarked by Dr. 



[17^] 



