THE BLACK SLATE AT THE FALLS OF THE OHIO. 153 



The preceding remarks upon the Black slate, in connection with the Ham- 

 ilton limestones of the Falls of the Ohio, are the results of my personal 

 observations, and inferences therefrom. Similar conclusions had some time 

 since been arrived at by Prof. Cox, State Geologist of Indiana, regarding the 

 Black slate or shale of New Albany and other localities in Indiana, and were 

 published in his Reports of 1874 and 1875. In previous Reports this forma- 

 tion is referred to as Devonian Black slate, Black bituminous shales of Devonian 

 age, and New Albany black shale ; but in 1874 he refers the New Albany 

 black shale to the age of the Genesee slate of New York. This conclusion is 

 based upon the discovery, at Lexington, by Prof. W. W. Borden, of certain 

 fossils which are characteristic of the Genesee slate in New York, viz. : Leio- 

 rhynchus quadricostata, Chonetes lepida, Tentaculites fissurella [=Styliola], and 

 fragments of a large species of Cardiola [= Cardiopsis], not unlike C. radians. 

 The fossils previously known in this rock were a species of Lingula and a 

 Discina, which had not been considered by him sufficient evidence for deter- 

 mining the geological age of the formation. 



Prof. Cox, in his Report for 1875, describes the New Albany black shale of 

 Floyd, Clarke, Scott and Jennings counties as the "equivalent of the Genesee 

 shale of New York ; " and cites " Tropidoleptus carinatus and Chonetes coronata, 

 Con. (Hamilton group of New York)," as occurring in the dark gray limestone 

 below the New Albany black shale. 



In his Reports of 1874 and 1875 Prof. Cox has given numerous instructive 

 sections, which show the varying conditions of the formations associated with 

 the Black slate. In some instances this formation is represented as resting 

 directly upon the Corniferous limestone, or separated only by some beds of 

 inconsidenible thickness and importance. In one locality, half a mile north of 

 Lexington, the section gives as follows : 



Black slate 4to7feet. 



Oxide of iron 6 inches. 



Light gray, shalj •limestone with abundance of fossils, Spirifer gregaria,Sp. acuminatics, corals, etc. 4 feet. 



Lbneetone, darker, with fossils 8 feet. 



Corniferoua limestone, very white, with an abundance of characteristic fossils. . . . 6 feet.* 



* Report of 1874, pp. 128 and 129. See, also, p. 150, same Report, where the Black slate is represented 

 as resting on limestone containing Ccmocardium, Zaphrentis, Spirifer acuminatus, and other fossils. 



20 



