Winchel].] 



386 



[May 6, 



the data upon which my forthcoming conclusions are to rest, I introduce 

 here a complete list of the fossils of the Marshall Group, and its supposed 

 equivalents in other States. As introductory to this, however, and as 

 tending to exclude from consideration the series of shales which 1 have 

 designated the Huron grouj), I offer a few remarks upon the paleontology 

 of these strata as far as investigated. 



The following is a complete catalogue of the fossils thus far deter- 

 mined : 



Orthoceras Barquianum. Win. 

 Spii'ifera subattenuata, Hall. 



" medialis, Hall. 



" Huronensis, Win. 



" pharovicina, Win. 



" insolita, Win. 

 Retzia polypleura. Win. 

 Merista Houghtoni, Win. 

 Pleurotomaria Huronensis, Win. 

 Goniatites Whitei, Win. 



Rhynchonella Huronensis, Win. 

 Orthis Vanuxemi, Hall. 



'• crenistria? Phil. 



" lowensis? Hall. 

 Chonetes setigera ? Hall. 

 Cardinia complanata. Win. 

 Leptodomus clavatus. Win. 

 Solen prisons. Win. 

 Orthoceras gracilius, Win. 



Four of the foregoing species I have identified, more or less doubtfully, 

 with species from the Hamilton group. These are Spirifera subattenuata, 

 S. mediahs, Orthis Vanuxemi, and 0. loioensis. A species very similar 

 to 0. Vanuxemi exists, however, in the Waverly series of Ohio, and in 

 strata of the same age in Illinois and Missouri. Chonetes setigera (?) of 

 the list, ranges in New York from the Marcellus shale to the Genesee. 

 Leptodomus clavatus closely resembles a Orammysia, a genus ranging 

 from the Corniferous to the Chemung. The equivalencies of these rocks 

 are not very precisely indicated from the paleontological data. That the 

 formation is newer than the Genesee shale is demonstrated by its observed 

 superposition. The paleontological evidence indicates, at least, that the 

 fauna is older than that of the Marshall group ; and this is all that is 

 necessary. If this group of rocks is proven by stratigraphical superposi- 

 tion to be newer than the Genesee, it belongs either to the horizon of the 

 Portage and Chemung, or to that of the Marshall. If its stratigraphical 

 position, its lithological characters and its fossil remains indicate equally 

 that it is not to be embraced in the same group with the Marshall, no 

 alternative remains. The Huron group, above the Black Shale, must cor- 

 respond to the Portage and Chemung, or to some portion of them. 



The question is now narrowed down to this : — Having discovered a rep- 

 resentative of the Portage and Chemung groups in the Huron shales 

 and their equivalents, in Michigan and Ohio, ought we to unite with 

 these shales the Marshall sandstones and their equivalents, and thus em- 

 brace these also in the zone of the Portage and Chemung ? 



I have furnished lithological and stratigraphical indications that this 

 ought not to be done. Let us examine the paleontological evidence. 



