2 



at least three distinct and successive groups of beds of the 

 carboniferous limestone period. 



With my present knowledge of these limestones, I am able 

 to show the order of succession, and to some extent, the ge- 

 ographical area occupied by the different members of the 

 following section. This section is compiled from observa- 

 tions, made in the valley of the Mississippi river, from Bur- 

 lington in Iowa, to near the mouth of the Ohio ; and from 

 previous examinations made in Indiana and Illinois. 



The same formations having been traced southward through 

 Kentucky, Tennessee and Alabama, I believe we have now 

 a definite conception of the members which constitute the 

 great carboniferous limestone formation, which in one or 

 other of its members extends from near the centre of Iowa 

 on the northwest, through Illinois and Indiana to the south- 

 west, and south through Missouri, Arkansas in part, Ken- 

 tucky, Tennessee and Alabama.* 



I am satisfied that a more careful study of the fossil re- 

 mains from these beds will sustain the view I have taken ; 

 and we shall hereafter recognize each of these groups as 

 possessing its own fauna, which to a great extent will prove 

 distinct from all the others. 



VII. Coal measures. 



VI. Kaskaskia limestone, or Upper Archimedes limestone. 



Localities. — Kaskaskia and Chester, 111. ; St. Marys, Missouri, etc. 



V. Gray, brown or ferruginous sandstone, overlying the 

 limestones of Alton and St. Louis. 



Localities. — Below St. Genevieve, Missouri ; Between Prairie du Rocker and 

 Kaskaskia, Illinois. 



IV. St. Louis limestone, concretionary limestone. 



Localities. — Highest beds below Keokuk, la. ; St. Louis,Mo. ; St. Genevieve. 



III. Arenaceous bed ; 



Second Archimedes, or Warsaw limestone ; 

 Magnesian limestone. 

 Localities. — "Warsaw, above Alton, 111. ; Spergen Hill, Bloomington, Ind. 



* I have in another place acknowledged my obligations to Mr. A. H. Wor- 

 then of Illinois, who aided me in tracing out and determining these groups. 



