152 PALEONTOLOGY OF NEW YORK. 



if at all from the Lingula spatulata of the Genesee slate of New York ; and the 

 Discina truncata, a characteristic fossil of the Genesee slate, is associated with 

 this Lingula in several localities near the Falls of the Ohio. In some specimens 

 of the Black. slate from near Lexington in Scott county, Indiana, I have found 

 well marked specimens of Choneles lepida, and a species of Leiorhynchus which 

 does not differ in any distinctive characters from L. quadricostatum. Both these 

 fossils are well known forms of the Genesee slate in the State of New York. 



In the same association in Indiana, I find the slaty laminae covered by 

 innumerable individuals of a species of Styliola, which is indistinguishable 

 from one known in the Genesee slate and in some calcareous bands above, as 

 well as in the succeeding green shales of the Portage group. In central and 

 western New York this minute fossil constitutes, of itself, layers several inches 

 in thickness, which are consequently calcareous ; and it is also, in some places, 

 disseminated through the slaty layers to such a degree as to render them very 

 calcareous and extremely fragile. 



From the above considerations I am led to the conclusion that the Black 

 slate of the west is the equivalent, and even the absolute continuation, of the 

 black shales succeeding the Hamilton group of New York (the Genesee slate), 

 carrying as it does identical species of fossils, and holding the same geological 

 position. 



It is not necessary, at the present time, to enter into the discussion of the 

 age of the succeeding deposits in the west, — the digression here made from the 

 purpose of this work being simply intended to aid in the determination of the 

 geological horizon, to which many of the fossils of this volume are to be 

 referred, and to set at rest, if possible, some difficulties in the way of a proper 

 understanding of the range of certain species of fossils in these portions of 

 the geological series. 



