194 Cincinnati Society of Natural History. 



character of the fossil remains, we refer all the strata containing the 

 Triarthriis hecki to the age of the Utica Slate Group of New York. 



Above the range of the Triarthrus hecki, the fossils, as well as the 

 position of the rocks, indicate the age of the Hudson River Group of 

 New York, and we have no hesitation in so referring them, and enter- 

 tain no doubt of the correctness of the reference. 



The fossils from Paris, Lexington, the High Bridge over the Ken- 

 tucky' River, and from other places in Kentucky, as well as the 

 lithological character of the strata, furnish abundant evidence of 

 the existence of the Trenton Group over an extensive tract of countr}-, 

 in that State. In the State of Kentuck3', we have the Trenton, Utica 

 Slate and Hudson River Groups well represented, and the rocks have 

 a northerl}' dip from Paris and Lexington, toward the Ohio River, 

 but at what rate per mile we are not advised. 



In South-eastern Indiana, neither the Trenton nor Utica Slate appear, 

 and, consequently, we refer all the Lower Silurian rocks of that State to 

 the Hudson River Group. 



The Trenton Group is not exposed at Cincinnati, nor at an}- point 

 in Ohio west of the city, but we think it is probable that it ma^'^ be 

 represented in the banks of the Ohio river a few miles east of the cit}^ 

 The Utica Slate is represented in Ohio onl^^ in the banks of the river, 

 at the cit}' of Cincinnati, and east of the city, and in the excavations 

 near the mouths of the streams which enter the river east of the cit}'. 

 Consequently, all the Lower Silurian rocks in South-western Ohio 

 belong to the Hudson River Group, except those represented by the 

 small exposures in the l)anks of the river at Cincinnati, and east of 

 the city, in the immediate vicinity of the river. 



The conclusion to which we have come is, that all the Lower Silurian 

 rocks, which we have had under consideration, are to be referred to the 

 Trenton, Utica Slate and Hudson River Groups, and that the name 

 " Cincinnati Group" should be dropped, not only because it is a syno- 

 nym, but because its retention can subserve no useful i>urpose in the 

 science, and because it will, in the future, as in the past, lead to erro- 

 neous views and fruitless discussion. And we would add that so far as 

 any investigations of these rocks have been made, they have not led to 

 any other or further subdivisions than those which we have adopted, 

 and which have been so thoroughly and firmly established by the geo- 

 logists of the State of New York. 



S. A. MiLLEU, A. G. Wetherby, 



Fred. Braun, Geo. W. Harper, 



JnO. MlCKLEIiOKOUGII, PaUL MoUR, 



John W. Hall, Jr., C. B. Dyer, 

 E. O. Ulrioh, R. M. Byrnes. 



