526 



R. T. HILL — THE COMANCHE SERIES. 



subdivisions, because I am not yet in possession of any very clear ideas upon 

 that subject. It is only intended to show graphically the effect of the as- 

 sumed correlation to which I have referred ; that is, if we draw a line from 

 the space representing the Dakota to that representing the Cenomanian, and 

 another line from the space representing the Comanche to the upper part of 

 the one representing the Turonian, they will cross each other. The shifting 

 of the relative position upward or downward of the right-hand and left-hand 

 portions of this table to meet the views of different persons as to the general 

 correlation of the American and European Cretaceous will not affect the 

 fact intended to be expressed by the crossing of the lines between them. 



Montana group. 



Colorado group. 



Dakota group. 



{Hiatus. ) 



Comanche Series. 



Danij 



Senonian. 



Turonian. 



Cenomanian. 



Gault. 



Neocomian. 



Many similar cases of theoretical paleontology at fault might be cited, to 

 some of which I have already called attention in my writings, but which I 

 have not now time to consider. I think I am justified in saying that theo- 

 retical attempts like these at special correlation of subdivisions of any geo- 

 logical system for different continents are unscientific, and, with due respect 

 to those who hold different views, that it is time we were done with them. 



Professor Hill : All analogies between the American and European for- 

 mations seem to cease when we reach the Comanche group ; yet there are 

 many species of the Comanche which are almost indistinguishable from 

 European forms, and afford the paleontologists of the old world a founda- 

 tion for their attempted correlations. 



Mr. C. D. Walcott : Professor Hill has brought up the question debated 

 by many geologists — whether the Cretaceous and later formations ever ex- 

 tended over the central Paleozoic area of Texas. A few years since I ex- 

 amined the latter rocks of this area and saw the escarpments of the Creta- 

 ceous strata facing the central Paleozoic area. As the last report of the 



