Gress : Fossil Plants of the Dakota. 277 



mations, to pass conformably upward into the Colorado division and 

 to rest upon earlier Cretaceous (Comanchean) beds. In some places, 

 however, it overlaps the earlier Mesozoic and Paleozoic formations 

 and rests on the Archean (Chamberlain and Salisbury's Geology, Vol. 

 Ill, p. 144). 



The present position of the Dakota Formation is now known to be 

 in the Upper Cretaceous, and, as has been shown in the Rocky Moun- 

 tain and Texas regions, the Lower Cretaceous, or what has been called 

 the Comanchean Series, lies between the Dakota and pre-Cretaceous 

 formations. Thus it will be seen that the meaning and application of 

 the term " Dakota "' is not exactly the same as it was when it was first 

 used by the author. ( " The term ' Dakota,' its origin, definition, and 

 application." 21st Annual Report, U. S. Geological Survey, Part 7, 

 1899, 1900, p. 318.) 



The term Dakota may still be used in a more limited sense, as is 

 shown by the fact that Ward in 1893 discovered that the Dakota 

 sandstone of the Black Hills contained not only a Dakota flora, but 

 other floras of later age. The stratigraphy showed that the upper 

 sandstone is separated from the lower by an intermediate layer of 

 shale which was called the Fuson Formation. The lower layer of 

 sandstone was called the Lakota Formation. The term Dakota was 

 applied only to the uppermost layer of sandstone (Darton, U. S. Geo- 

 logical Survey, Professional Paper No. 32, 1905, p. 165). 



" The tripartite composition of the old ' Dakota ' group in the Black 

 Hills is very distinct throughout the uplift and apparently is a wide- 

 spread feature in the adjoining regions." (Darton, op. cit.) The 

 Fuson and Dakota beds are classified by Knowlton as correlated with 

 the Kootenai and the Morrison of the Comanchean Period. (See 

 "Plant Successions" by Clements, 1916, p. 443; also Cleland, "Geol- 

 ogy Physical and Historical," 191 6, p. 515.) 



Botanically the history of the " Dakota Formation " begins with 

 1866, when leaves, collected by Messrs. Marcou and Capellini, were 

 figured and described under seventeen different species by Professor 

 Heer in a paper entitled " Les Phyllites Cretacees du Nebraska." 



In 1868 Dr. Newberry described some leaves collected by Meek and 

 Hayden from the " Dakota Formation." A series of plates was made 

 which was intended to be published in Volume VIII of the Geological 

 Survev of the Territories, but this was not done. 



