jR. T. Rill — Texas Section of American Cretaceous. 289 



concerning the American Cretaceous does not justify any more 

 specific term to these as a whole than " The Middle Cretaceous." 



In all four of the regions above mentioned the undoubted 

 open sea or marine groups rest upon the problematical forma- 

 tions of more shallow sediments, consisting of clays and sands, 

 unaccompanied by any distinctive molluscan faunas, but a great 

 abundance of vegetal remains : such as the Dakota sandstone in 

 the Rocky Mountain region, the Eutaw clays in the Alabama 

 region, the Potomac beds in the Virginias, and the Raritan 

 clays, in New Jersey the relation of which to each other has 

 not been published and is still a fertile question for investiga- 

 tion.* 



The Dakota sandstone was erroneously thought, by Mr. Meek, 

 to be identical with the Raritan clays of New Jersey, and Pro- 

 fessor E. D. Cope has suggested that the Lower Cross Timber or 

 Dakota Group of Texas was equivalent to the Eutaw Group of 

 Mississippi. These as well as the Potomac formation of Rogers 

 in the Virginias, and the Raritan clays of New Jersey, have 

 been placed separately by many writers at the base of the 

 Cretaceous series. If the Lower Cross Timber sands be of the 

 age of the Dakota sandstone, as has been asserted by Shumard 

 and others, and since when present they rest directly on top of 

 this division, then we have in Texas not only the whole section 

 of previous writers often visible in connected exposure, but a 

 new and lower group of the marine Cretaceous beneath the 

 hitherto recognized groups. 



In this Journal of January, 1887, I first called attention to 

 the fact that the current ideas of the relations of the Cretaceous 

 strata of Texas were erroneous. In a paper read before the 

 Philosophical Society of Washington, \ January 29, 1887, I 

 published a local section, typical of the whole region, includ- 

 ing the strata from the Tertiary to the Carboniferous, and a 

 condensed summary of the paleontology, stratigraphy and lit- 

 erature of the Cretaceous strata of Texas. I demonstrated the 

 transitional position these strata occupied between the Atlantic 

 States bordering upon the Gulf of Mexico and those of the 

 Rocky Mountain region, and showed the existence there of a 

 deep marine group of the Cretaceous which is older than any 

 hitherto recognized on this continent. In a paper read before 

 the Philadelphia Academy of Science, February 5, 1887, Dr. 

 C. A. White published a resume* of the section furnished him 

 by me for that purpose together with some brief deductions 

 thereon and some correlations of his own. In the present 



* Some important unpublished observations, which the writer does not feel 

 authorized to use, have been mads of late in these basal groups by McGee, 

 Fontaine, Smith, Johnson and others. 



\ " The Topography and Geology of the Cross Timbers and Surrounding 

 Kegions of Northern Texas." See this Journal, April, 1887. 



Am. Jour. Sci— Third Series, Vol. XXXIV, No. 202.— Oct., 188T. 

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