68 Kansas Academy of Science. 



to an enormous transgression of the sea over the land, one of the 

 greatest in all recorded geological history. Over the region of the 

 Great Plains the Upper Cretaceous was inaugurated by the forma- 

 tion of a nonmarine stage, the Dakota." ' 



This seems at first discordant with the table, but, in the light of 

 it, he may mean that the terrestrial Dakota — formed over the Great 

 Plains contemporaneously with the upper portion of the marine 

 Comanche further south — seems in that region to begin the 

 Upper Cretaceous, but in no other way could a nonmarine forma- 

 tion be said to inaugurate a marine formation. Hence, logically, 

 the division between the Lower and Upper Cretaceous should be 

 above the Dakota rather than below it. 



In view of these facts, it is with surprise that we find that 

 Chamberlin and Salisbury's "College Geology," recently published, 

 distinctly places the division between the Lower and Upper Cre- 

 taceous below the Dakota, and, moreover, makes it a break between 

 periods instead of epochs as heretofore, though the authors are 

 constrained to add that "north of Texas the formation (Dakota) is 

 in apparent conformity with the Comanche in some places; though 

 in others, as in the Wasatch and Uinta mountains, it rests on older 

 form'ations.""* They are, as a result, betrayed into figuring a cycad 

 from the Dakota as illustrating Comanche life. 



The results of our research may be briefly summed up as follows: 



All the students of the Dakota formation seem now to be agreed 

 that it is mainly Lower Cretaceous in age, and most recent writers 

 on the subject express themselves to that effect, while some have 

 referred the whole of it to that epoch. 



That the latter position is right seems clear for the following 

 reasons: 



1. From the standpoint of stratigraphy, it is questionable whether 

 much, if any, of the present Dakota sandstone was laid down con- 

 temporaneously with any of the marine Upper Cretaceous. No 

 doubt there were terrestrial deposits laid down over the Great 

 Plains, while marine beds, now recognized as Upper Cretaceous, 

 were forming in southern Texas or Mexico; but in the later trans- 

 gression of the sea northward several feet in thickness of such beds 

 must have been cut away by the wave action and rearranged in the 

 Benton of the Upper Cretaceous, as Grabau argues. This may 

 have removed all which was formed on the land during such trans- 

 gression, and should it ever be found to be otherwise, still the 



7. Int. to Geol., pp. 702. 705. 



8. Coll. Geol., p. 747. 



