The Rise of the Mammals 



oped, lacking in convolutions, and not sharply- 

 marked off from the cerebellum. 



The fossils of the Eocene are found in what 

 were then the beds of a series of great lakes 

 that during that period successively occupied 

 portions of the West. The Puerco, Wasatch, 

 Bridger, and Uinta series, consisting ^principally 

 of hardened sands and clays, represent the 

 deposits that formed in these bodies of water, 

 and in them is preserved an almost continuous 

 record of the life of the Eocene period. The 

 great Wasatch Lake was the largest of them, 

 and extended from New Mexico, over eastern 

 Utah and western Colorado and Wyoming to 

 the Wind River Mountains, a distance of 450 

 miles. It had a breadth of 250 miles, and was 

 altogether a goodly body of Avater. 



As may be imagined, our Western territory 

 was a very different place then from what it is 

 now ; the uplift of the Rocky Mountains and 

 central plains had not gone far enough to cut 

 off the moist winds from the Pacific, wdiile at 

 the same time draining the lakes ; the climate, 

 as we gather from the plants and insects, was 



231 



