788 



GEOLOGY 



herbivores and the clawed carnivores soon became distinct. The 

 condylarths (Fig. 529) were small generalized forms with five toes 

 and forty-four teeth, not yet developed into the true herbivorous 

 type. They have lived on till now without radical change, but 

 one branch, adapted to forests and marshes, seems to have diverged 

 early, and to have given rise to the ungulates. In the course of 

 the period many of them became fitted for life on grassy plains. 



Fig. 529. A primitive ungulate or condylarth of the Wasatch epoch ; Phcn- 

 acodus primcevus Cope, about ^3 natural size (about the size of a tapir. 

 from Big Horn basin, Wyoming. (Cope.) 



To this end, there was a progressive abandonment of the flat, heavy, 

 palmate form of foot, and the acquisition of the light, spriiury. 

 digitate habit, adapted to a quick start and swift flight. At the 

 same time hard hoofs, and powerful grinding teeth were developed. 

 The evolution of hoofs and grinding teeth has been thought t<- 

 connected with the prevalence of grassy plains, the firm turf of 

 which is in contrast with the soft soil of forest and marsh. ( Ira - 

 also are much associated with dry and even semi-arid grounds, and 

 dessication intensifies the firmness of the bottom, and <rivos addi- 

 tional occasion for the hoof. The forests perhaps helped to pre- 

 serve a section of the evolving order in its more primitive form. 



Back of these influences lay the physical conditions that pro- 

 moted them. In western America, where the evolution is best 



