INTRODUCTORY REMARKS. 



XX XIX 



The column on the righi is here added to indicate what arc, believed to 

 be Hie Upper Missouri equivalents of the subordinate groups shown in the 

 above section. If these views are correct, there would appear to be no 

 representation here of (lie Fort Benton and Niobrara groups of the Upper 

 Missouri section, so extensively developed in Texas, New Mexico, and other 

 south western districts west of the Mississippi. Probably, however, one or 

 both of these may be represented here by the division II. The evidence that I, 

 of the above section, aside from its position, is the equivalent of the Dakota 

 group of the Upper Missouri, is not so decided as that the beds III and IV 

 represent the Upper Missouri, Fort Pierre, and Fox Hills groups. 



As far back as May, 1857, in a paper published by the author in con- 

 nection with Dr. Hayden in the Proceedings of the Philadelphia Academy (vol. 

 ix, page 127), the opinion was expressed that at least three of the Upper Mis- 

 souri Cretaceous subdivisions arc represented in Alabama. In order to 

 illustrate this parallelism more clearly, the following section of these rocks 

 in that State, from facts furnished by Prof. A. Winched, was given on page 

 126 of the paper above cited : 



Alabama section, from facts communicated by Prof. A. Winchell. 



* Now known as Placenticeras lenticularis, Owen (sp.). 



