14 GEOLOGY OF OHIO. 
Professor Alexander Winchell, and was by him associated with some 
overlying greenish sandstones and shales, to form what he called the 
Huron Group. The upper portion of that group has, however, since been 
proved py its fossils to belong to a more recent formation, and is said by 
Professor Rominger to be Lower Carboniferous, and to represent a portion 
of our Waverly group. In these circumstances, it was thought best to 
retain Professor Winchell’s name, but to limit it to its most important 
representative in Michigan—the Black shale, which, although widely 
and well known, had before received no distinctive geological appella- 
tion. Hence it has been designated in all our reports as the Huron shale. 
By different writers on the geology of the western States, it has ‘been 
referred to, sometimes, as the western extension of the Marcellus or the 
Genesee, or a union of both.* Professor Dana, in the last edition of his 
“Manual,” page 268, refers to it as “‘the Black shale or Genesee shale ;” 
Professor H. T. Cox, in his report on the Geological Survey of Indiana, 
1875, page 169, speaks of it as the ‘“‘ New Albany black shale, equivalent 
of the Genesee shale of New York, and reports it to contain Leiorhynchus 
guadricostata, Iingula spatulata, Tentaculetes fisswrella, and Chonetes lepida, 
all of which are fossils of the Genesee. 4, 
In the discussion of the age of the Hudson shale, contained in Volume 
i, page 152, 1t is shown that it is not the equivalent of the Marcellus — 
shale, since in Ohio it overlies unmistakable Hamilton limestones; and 
it is argued that it cannot be the representative of the Genesee exclu- 
sively, as where last observed by Professor Hall, in Western New York, 
the “ Genesee slate” is only twenty-two feet in thickness, and is thin- 
ning westward ; and because we have found in our Black skale character- 
istic Portage fossils—Clymenita complanata, Avicula speciosa, and Orthoceras 
aciculum 
The conclusion reached in the discussion referred to, was that the Huron 
shale of Ohio 7s made wp of the black shales of the Lower Portage and the Genesee. 
Subsequent examination has fully confirmed this view, and has fur- 
nished what may be accepted as demonstrative evidence of its truth. 
In the central and southern part of the State, the Huron shale is a 
nearly homogeneous mass, containing no argillaceous shales or sand- 
stones. Recently, a number of borings have been made along the lake 
shore, at Norwalk, mouth of Black River. Berea, Brighton, Cleveland, 
* Professor Lesley, in his appendix to Mr. Carll’s report, calls the Huron shale Hamil- 
‘ton; but, as will be seen further on, although forming a natural continuation of the 
Hamilton Group upward, and, therefore, belonging to the Hamilton chapter in Geologi- 
cal history, it is not the equivalent of any portion of the Hamilton Group of the New 
York geologists. 
