222 Kansas Academy of Science. 



the downward movement and maintain the area as land. The 

 shell limestone marks a time when subsidence may have gained 

 on the infilling, which subsequently increasing in relative im- 

 portance, filled the shallow sea with sands and muds. Sub- 

 sidence again dominating over infilling, led to the deposition of 

 the Mentor beds, filling up the sea once more, following which 

 the Dakota beds of continental origin were deposited. 



The second problem concerns the relations of the Dakota to 

 the Comanchean. The earliest sands of the Dakota appear 

 identical in lithology to those of the Mentor and conformable 

 thereto. They appear to be those left on the deposits of a 

 vanishing sea by an advancing of the continental deposits. 

 Are these continental deposits of Comanchean or Cretaceous 

 age? It is hoped that an answer to this question may later be 

 attempted. 



The third problem meets the difficulty that hardly anything 

 is known of the deposits which lie underneath the Cretaceous 

 areas to the west, but it is known that a thin edge of Coman- 

 chean strata is present near Canyon City, Colo., as well as at 

 other localities in that state (13:657). These western de- 

 posits contain many species identical with those of the Coman- 

 chean of central Kansas, and it must be that either the sea ex- 

 tended directly over from Kansas to Colorado or swung south- 

 ward. Which is the case remains to be determined. 



