148 
PALEONTOLOGY OF NEW YORK. 
NOTE ON THE BLACK SLATE SUCCEEDING THE HAMILTON LIMESTONES AT THE FALLS 
OF THE OHIO. 
The Black slate, known under that name alone, in the vicinity of New 
Albany, Jeffersonville, and many other places in the southern part of Indiana, 
has been recognized in all the published sections of the strata at the Falls of 
the Ohio. It has usually been regarded as of Devonian age, but has sometimes 
been claimed as belonging to the Carboniferous series. Evidences of its true 
geological age and its equivalency with known sedimentary formations in the 
east must be sought in its fossil contents and its geological relations, since its 
direct continuity cannot be traced. 
In order to come to this point with some preliminary appreciation of the 
subject, it may be remarked that the results of all our geological investigation 
have shown a gradual (occasionally an abrupt) thinning, in a westerly and south¬ 
westerly direction, of all the sedimentary formations which lie between the 
Upper Helderberg limestone and the base of the coal formation. In New York 
and Pennsylvania, these are represented by coarse and fine shales and sand¬ 
stones, the coarser materials predominating. At intervals there occur beds, 
greater or less in extent, of fine sandstone, slate or shale; and these become 
more marked and conspicuous in a westerly direction; while gradually the 
arenaceous deposits give way, and the whole mass becomes finer in character 
and greatly diminished in its aggregate thickness. In the course of several 
hundred miles, not only do the arenaceous, littoral portions of the deposit 
give place to finer sedimentary materials, but calcareous matter supervenes, 
either as a general admixture with the shale, or as continuous belts of distinct 
concretions, or of concretionary or other forms of limestone bands, forming an 
important feature in the geology. 
Although a full discussion of the different conditions in which these deposits 
present themselves in their westward extension would occupy much more space 
age of the Hamilton group, associated with Orth is suhorhicularis, Atrypa reticularis , A. aspera, Euomphalus 
cyclostomus ? etc. This is about the same horizon in which Hall found his Megistocrinus latus.” 
This is the only reference of any of these fossils to the Hamilton group which I have been able to find 
among the writings of Lyon and Casseday, or of Major Lyon. 
