180 THE DEVONIAN AND CARBONIFEROUS. [bull 80. 



" Mississippian series " for the formations grouped under the names Sub- 

 carboniferous or Lower Carboniferous are given in a previous chapter. 



This " Mississippi limestone series " of Winchell includes the rocks 

 in the Mississippi Valley from the " Burlington" up to the "Kaskaskia" 

 of Iowa, and in his usage it does not include the "Kinderhook" or 

 " Waverly." But to be of practical use the series should extend from 

 the base of the Carboniferous, i. e., including the " Gouiatite beds," the 

 " Chouteau series," the " Kinderhook," the "Marshall," the " Waverly," 

 upward to where the marine fauna ceases at the approach of the con- 

 glomerates or similar deposits heralding the appearance of coal. 



In discussing this group, Winchell only identified, with little argu- 

 ment, the "Carboniferous limestone" of Michigan, the "Knobstones" 

 of Indiana and Kentucky, and the " Siliceous group " of Tennessee, 

 with the "Carboniferous limestone" of the Mississippi Valley, not 

 including here, however, the formation next to be considered. 



The rocks between the " black shale " and the " Mississippi lime- 

 stone" above presented greater difficulties, because of the radical 

 lithologic differences of the various outcrops representing them. The 

 several formations are the " Waverly " and " Gritstone " series of Ohio, 

 the Chemung and Portage groups of New York, the " Marshall sand- 

 stones" of Michigan, the "Yellow sandstones," called in the earlier 

 report " Chemung group," of Iowa, the " Rockford limestones" of Illi- 

 nois, and the " Chouteau limestones, Vermicular sandstone and shale, 

 the Lithographic limestone " of Missouri. 



The general equivalency between the Waverly and Gritstone series 

 of Ohio and the Portage and Chemung of New York had been asserted 

 by James Hall, and, following his authority, had been the usage of 

 geologists for years. From this position Winchell both departed and 

 advanced. In Michigan he recognized below the Marshall sandstones, 

 and above what he regarded the equivalent of the Genesee shale of 

 New York, some 500 or 600 feet of argillaceous rocks, more arenaceous 

 and flaggy to the north. Tbese, which he called the " Huron group," 

 he considered as the equivalent of the Portage and Chemung of west- 

 ern New York. 



In Ohio, below the Waverly series, he found the extension of his 

 Huron group [what is now called the " Erie shales"], equivalent to the 

 Portage and Chemung of New York. On similar grounds, which are 

 lithologic and stratigraphic, he identified the argillaceous beds above 

 the black shale in Kentucky with his Huron group. He also referred 

 to a similar horizon the " bluish, slightly micaceous sandstones of the 

 yellow sandstone series of Iowa, the blue shales below the lithographic 

 limestones of Missouri, and possibly the Illinois shales doubtfully 

 referred to the Genesee by Prof. Worthen ; " and having thus, on phys- 

 ical grounds, found what he thought to be equivalent formations to 

 represent the Chemung and Portage of New York, he presented a 

 lengthy argument for regarding the Waverly series of Ohio and the 





