iriLUAMs.] WINCHELL ON THE MARSHALL GROUP. 179 



jower Carboniferous system." 1 He next gave a brief synopsis of 

 opinions under the Leading of "History of discovery and opinions," 

 )egiuning with Hildreth's paper, 1836, 2 and citing tlic views of the chief 

 contributors to the discussion up to 1869. Then follows a tabulation of 

 the rock sections, as then interpreted, in the several States, including 

 the corresponding sections of the States of New York, Michigan, Ohio, 

 Indiana, Illinois, Iowa, Missouri, Kentucky, and Tennessee. He then 

 proceeded to discuss "the parallelism of the formations on purely 

 structural aud lithological grounds," and remarked that " the identity 

 of the black shale can not now be mistaken." He referred to its 

 demonstrated position above the Hamilton group in Michigan, Kentucky, 

 aud Ohio, and below the Eockford Goniatite beds in Indiana. He 

 thought it was unrepresented in Missouri. In Michigan it may be the 

 lower part of his Huron group, and in New York he confined the typical 

 equivalent of the black shale to the Genesee shale on paleontologic 

 grounds. 



The Carboniferous conglomerate was next taken as marking u a 

 superior horizon which can not ordinarily be mistaken." The Parma 

 conglomerate of Michigan the author considered as "stratigraphically 

 equivalent to the carboniferous conglomerate." Lithologically he 

 found no means of distinguishing the coal conglomerate of Ohio from 

 the Chemung and Catskill conglomerates of New York. On paleon- 

 tologic grounds, however, he separated the u Chemung" and Catskill 

 conglomerates, which he made equivalent to the " Marshall group" of 

 Michigan, from the " Parma conglomerate," which he placed higher in 

 the scale above the carboniferous limestones of the interior; and after 

 discussing the fossils underlying or associated with the conglomerates, 

 he said : 



"For these reasons I shall, for the present, regard the three conglomerates 3 in 

 western New York, with the associated strata, as belonging together in the horizon 

 of the Catskill group." 



Later investigations, particularly those of the Second Pennsylvania 

 Survey, have thrown clearer light on the relations of these several 

 conglomerates. 4 



The third conspicuous formation which Winchell sought to correlate 

 was the " Carboniferous limestone series " of the Mississippi Valley. 

 In a foot-note 5 the author proposed the name "Mississippi limestone 

 series or Mississippi group " for the " Carboniferous limestones of 

 the United States, which are so largely developed in the valley of the 

 Mississippi." My adaptation of this name and proposal of the name 



1 The Marshall group : A Memoir on its geological position, characters, and equivalencies in the 

 United States. Proc. Am. Phil. Soc, vol. 11, 1869, p. 57. 

 'Am. Jour. Sci., vol. 29, 1836. pp. 133-136. 



3 Viz, the " Chemung conglomerate," the " Catskill conglomerate," and the so-called " Carboniferous 

 conglomerate," near Panama. 



4 See Second Pennsylvania Survey Reports III, by J. F. Carll, 1880, and Report R, by C. A. Ash- 

 burner, 1880. 



• Proc. Am. Phil. Soc, vol. 11, p. 79. 



