THE EOCENE PERIOD. 



233 



in the Dinoceras, brute-mass and low brain-power seem to have reached 

 their mammalian climax, much as they had reached a a earlier climax 

 in the monster reptiles. Nearly all dominant forms thereafter showed 



Fig. 428. — One of the Amblypoda of the Lower Eocene (Wasatch) Coryphodon Jta ma- 

 ins, restoration of skeleton by Marsh. About T V natural size. For skull and 

 brain see Fig. 430a. From Wyoming. (After Marsh.) 



notable increase in the size and complexity of the brain, and from this 

 time on there was a gradual transition from the dominance of brute- 

 force to the dominance of the brain-power. 



Fig. 429. — Dinoceras mirabile, restoration of skeleton by Marsh, about 13 feet long, 

 Middle Eocene, Wyoming. (After Marsh.) 



The divergence of the ungulates into odd- and even-toed. — Early in 

 the Eocene, the hoofed animals began to diverge into their present divi- 

 sions, the odd-toed (perissodactyls) and the even-toed (artiodactyls). 



