wiLUAMs.l WINCHKLL ON THE MARSHALL GROUP. 177 



Ohio occupying the interval between the "Grit" No. 4 and the " Cliff 

 limestone" No. 6. 



In the same year J. W. Foster reported the absence in Ohio of the 

 representative of the conglomerates of New York State. The "Cliff 

 limestone" he thought should be divided on biologic grounds. The 

 sandstone formerly known as the " Waverly" should for like reasous 

 be divided into three parts. The fossils have more Carboniferous than 

 Devonian affinities. 



The rocks of the Ohio coal field consist of sandstones, shales, lime- 

 stones, seams of coal, and buhrstone. The limestones and sometimes 

 the shales contain exclusively marine faunas, while the sandstones con- 

 tain a Carboniferous flora. The alternations of marine and terrestrial 

 remains were noticed in a vertical distance of 700 feet. The faunas 

 and floras contained in each formation were described in detail. 1 



In 1862 James Hall 2 began to see the incorrectness of his correlation 

 of the Waverly group and wrote : 



The Waverly sandstone group of the Ohio Reports, at one time regarded as entirely 

 equivalent to the Portage and Chemung groups, may in its upper members constitute 

 a distinct group, though we do not yet know any line of demarkation between them. 



From 1862 to 1870 Alexander Winchell wrote several papers bearing 

 upon the correlation of the Marshall group of Michigan. The fossils in 

 this group proved to be closely related to those of the Waverly fauna, 

 and thus the problems of the Marshall group of Michigan became inti- 

 mately associated with those of the Waverly group of Ohio. In 1862 

 he briefly described the rocks of this group in lower Michigan, and their 

 fauna. 3 



The following is a synoptical view of the strata described : 



Feet. 



Carboniferous limestone 66 



Michigan Salt group 184 



Napoleon group 123 



Marshall group 173 



Huron group 210 



Hamilton group 55 



The rocks chiefly interesting him in this paper were a series of fine, 

 friable, ferruginous sandstones not over 300 feet in thickness, whose 

 upper portion, more grayish, firmly cemented, and homogeneous than 

 the lower, is remarkably destitute of organic remains and is sepa- 

 rated from the lower by 15 feet or more of shale containing a large 

 amount of ferruginous matter. The lower portion of the sandstone is 

 rich in fossil remains belonging to the genera Goniatites, Nautilus, Or- 

 thoceras, Bellerophon, Nucula, Solen, Myalina, Ghonetes, etc. The upper 



1 On the alternations of marine and terrestrial organic remains in the Carhoniferous series of Ohio. 

 By J. W. Foster. Am. Assoc., Proc, vol. 6, pp. 301-304. 



»"On the Catskill group of New York." By James Hall. Canadian Naturalist and Jour, of Science, 

 new series, vol. 7, 1862, p. 381. 



•Notice of the rocks lying between the Carhoniferous limestone of the lower peninsula of Michigan 

 and the limestones of the Hamilton group, with descriptions of some cephalopods supposed to bo new 

 to science. Bv Alexander Winchell. Am. Jour. Sci., vol. 33, 1862, pp. 352-366. 



Bull. 80 12 



