WHITE ON PALEONTOLOGY. 

 THE UPPER MISSOURI RIVER REGION. 



609 



Cenozoic, or Tertiary . . < 



Post- Cretaceous 



Later Mesozoic, or Cre- 

 taceous. 



White Kiver Gi^oup. 



Wind River Group. 



Fort UnioQ Group. 



Judith Kiver Group. 



Fox Hills Group. 



Fort Pierre Group. 



Earlier Mesozoic . 



L 



Niobrara Group. 



Fort Benton Group. 



Dakota Group. 



Jurassic. 



Tbe parallelism of the Cretaceous and Jurassic groups in the two 

 regions respectively is unmistakable; but that of the higher groups 

 has not yet been clearly made out. The list shows, however, that three 

 of the species originally discovered in the Fort Union group have been 

 identified in the AVahsatch group in Utah, or in strata that are now 

 believed to be equivalent with that group. 



Besides the fossils that have been collected from these defined groups 

 of strata, the catalogue contains some others, that have been collected 

 from Tertiary strata at different localities in the great Rocky Mountain 

 region, which have not yet been correlated with the strata of any of 

 those groups. This is partly due to a want of knowledge of their strati- 

 graphical relations, and partly because those fossils are mostly of difi'er- 

 ent types from any found in the recognized groups ; and different also, 

 in part, from any types, either fossil or recent, yet found on this conti- 

 nent. A.S the scope of this paper is only intended to embrace the west- 

 ern interior portion of the North American continent, the corresponding 

 kinds of fossils that may have been discovered east of the Mississippi, 

 or upon the immediate Pacific slope, are not here enumerated. 



