94. GEOLOGY OF OHIO. 
The list of the fish remains procured in the black shale at Vanceburg, 
Kentucky, and on the Ohio side of the river, now includes two species of 
Ctenacanthus, one of Orodus, one of Cladodus, and one of Palzoniscus. With 
these were immense numbers of minute, teeth-like organs, which have 
been the subjects of much speculation among zoologists. These are 
almost microscopic in size, and consist of a base elongated horizontally, 
upon which are set a great number of acute denticles, forming a minia- 
ture comb or saw. They are generically identical with the group of 
organs first described by Pander, under the name of Conodonts, obtained 
from the Silurian shales of St. Petersburg, and subsequently found by 
Mr. More in great numbers in the Carboniferous limestone of England. 
By Pander they were considered to be the teeth of fishes, a conclusion of 
which the propriety is, however, questioned by Prof. Owen. By Agassiz 
they are regarded as the teeth of Selachians, and as closely allied to such 
forms as Ctenoptychius. It has also been suggested that they were the 
teeth of mollusks, to which they have great resemblance. They will be 
found figured and described in the Paleontological portion of this Report, 
and the reasons will be given there for the view I have taken of them, 
viz., that they are the dermal ossicles (the shagreen) of fishes. What- 
ever may be their zoological affinities, these Conodonts have a special 
geological value, as they are characteristic of the Cleveland shale wher- 
ever explored. In the section at Newburgh surfaces of the shale were 
found completely covered with them. In the same locality a species 
of Polyrhizodus was also found, and abundant ganoid scales, which are 
proved by specimens obtained at Vanceburg by Captain Patterson to 
belong to a species of Palzoniscus. From the different exposures of the 
Cleveland shale we have now gathered the following fossil fishes: Cten- 
acanthus formosus, N., found also in the Cuyahoga shale; Ct. furcicarinatus, 
N.; Cladodus Pattersont, N.; Orodus variabilis, N.; Palwoniscus, two species}; 
Polyrhizodus modestus, N., and Conodonts of various forms. 
To the paleontologist it is scarcely necessary to say that such a group 
of fossils as that enumerated above could only come from Carboniferous. 
rocks; most of the genera here represented being exclusively confined to 
that formation. The only exception is that of Ctenacanthus, of which 
one or two doubtful species have been described from the Devonian rocks 
of the Old World, and we have obtained one well marked. and beautiful 
species from the Huron shale (Ct. vetustus, N.). 
In the sections opened by the valleys of the Cuyahoga and its tribu- 
taries, the Cleveland shale is underlain by a few feet of impure lime- 
stone and argillaceous shale. The limestone contains Syringothyris typa, 
Macrodon Hamuiltomex, and other Waverly fossils. Beneath these strataare — 
