IT" 



(M.OLOLiV OF THE DENVER BASIN. 



Dakota group. 



This little table brings oul clearly a number of interesting things. It 

 appeal's that 12 of the 29 species found in Colorado arc confined to these 

 two localities: thai is, have never been found outside of the Denver Basin, 

 rhis proportion ol endemic species is very large and suggests the proba- 

 bility of finding much new material when the beds can be thoroughly 

 exploited. 



Of the 17 species having a more or less wide distribution, !• are found 

 also in Kansas, 7 in the Andioy clays of New Jersey, and 5 in Nebraska, 

 with one of two each in Iowa. Minnesota, and the Laramie of various 

 place- l'p to thi' present time very little has been done toward the differ- 

 entiation of horizons in the Dakota group. A few of the species are 

 known to be common to two or more localities, hut the larger part are 



