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 Palxoniscus. 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 Palseontological 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 Palxoniscus. Prom 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 Pattersoni, N. ; Orodus variabilis, N. ; Palxoniscus, 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. mtustus, 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 Hamiltonias, and other Waverly fossils. Beneath these strata are 



