276 Annals of the Carnegie Museum. 



given to the series and subdivisions (Proceedings Academy Natural 

 Sciences of Philadelphia, p. 419) : 



Upper Series. 



Formation No. 5, Fox Hill Group. 

 Formation No. 4, Fort Pierre Group. 



Lower Series. 



Formation No. 3, Niobrara Division. 

 Formation No. 2, Fort Benton Group. 

 Formation No. i, Dakota Group. 



This is undoubtedly the first use of the term '' Dakota." As is 

 shown, this formation was from the first included in the Cretaceous, 

 although some writers, particularly in Europe, thought it belonged to 

 the Miocene Age, while others placed it in the Triassic or Jurassic. 

 For a detailed account of the great controversy which took place con- 

 cerning the age of the Dakota Formation see Gould, Charles Newton, 

 The Dakota Cretaceous of Kansas and Nebraska, Kansas Academy 

 Science, Transactions, XVII, 1901, pp. 122-178. Also Bain (Iowa 

 Geological Survey, V, 1895, P- 267), who gives an excellent review 

 of the Dakota Formation of Iowa, including a great many references. 



While the name has not been changed, still very much more is 

 known about the exact relationship and boundary lines of the " Dakota 

 Formation " than was known at the time the name was first used. 



In the U. S. Geological Survey, IX, Pis. i and 2, fossils are figured 

 from the alleged " Dakota Formation." One of these represents the 

 fauna of the typical Dakota locality in Nebraska, the other represents 

 the fauna of the Dennison beds of the Comanche series in Kansas, 

 the existence of this series not then being known in America. 



The author of the term " Dakota Formation " did not know that he 

 was including within it two distinct formations and faunas, as has 

 been proven by recent discoveries in the Texas region and other parts 

 of the Rocky Mountain region. 



The original definition and description of the Dakota Group were 

 based upon the Big Sioux River locality where the earlier Cretaceous 

 beds were not present. Since it was found in the type-locality to rest 

 upon pre-Cretaceous rocks, it was thought to form the lowermost 

 layers of the Cretaceous rocks. By more recent discoveries, it is now 

 known, where there have been no interruptions in the successive for- 



