Notices of Memoirs — Prof. Claypole — Devonian Pkicoderms. 473 



IV. — The Cladodonts ov the Upper Devonian of Ohio. By 

 Professor E. W. Claypole, D.Sc. (Lond.). 



NUMEEOUS specimens of tlie Cladodonts of the Cleveland Shale 

 in Ohio have been found by Dr. William Clark. They for the 

 first time reveal to ns the general form of the fishes to which 

 belonged the teeth that have alone so long represented the genus 

 Cladodus. The fossils are in very fair preservation, but their state 

 of pyritization has obscured many of the details of their structure. 

 So far as regards their form, however, we now know that they were 

 long, slender fishes, resembling in their character the sharks of the 

 present day; that they possessed well - developed and powerful 

 pectoral and caudal, with weak ventral fins, the dorsals being un- 

 known ; that they were for the most part, or altogether, spineless ; 

 that at least one species possessed cladodont teeth of more than one 

 pattern ; and that they had near the hind end of the body a peculiar 

 flat expansion or membrane of rudely semicircular form, which 

 gave to the caudal extremity when seen from above the outline 

 of a sharp-pointed shovel. 



The largest whole specimen yet found shows a fish of about 6 feet 

 in length, but detached teeth and other fragments indicate others of 

 double this size, and supply abundant proof that in late Devonian 

 times, and in the North American area, the elasmobranch fishes had 

 attained very great proportions and a high stage of development. 



Hitherto the Cladodonts have been regarded as, in the main, 

 characterizing the Lower Carboniferous rocks, but we now find them 

 abounding in the earlier Devonian strata, and, as shown by the 

 contents of their stomachs, preying — in some cases at least — on the 

 smaller placoderms of the same area. 



From the evidence of the new specimens it appears most likely 

 that the species already defined from single and isolated teeth can 

 no longer be maintained. 



For details see the papers in the " American Geologist " for 

 1893-4-5. 



V. — The Great Devonian Placoderms of Ohio, with Specimens. 

 By Professor E. W. Claypole, D.Sc. (Lond.). 



THE Upper Devonian Shales of Ohio have recently afforded 

 a remarkable series of fossil fishes rivalling in size and interest 

 those found many years ago in the Old Red Sandstones of similar 

 age in Scotland, and described by Agassiz and Hugh Miller. The 

 earliest of these, Dinichthys, was closely studied, and its structure 

 was well explained by the late Dr. Newberry. It was an immense 

 armour-clad fish, whose head measured from 2 to 3 feet in length. 

 TitanicJithjs, the second of the group, though less massive, was 

 of yet larger size. Gorgonichthjs, the third, was described by the 

 present writer in 1893, and, so far as is yet known, was the most 

 formidable of all, possessing jaws of enormous size and thickness, 

 above 24 inches long, ending in teeth or points from 6 to 9 inches in 

 length. The fourth and last, Brontichthijs, of which a description 

 was also published by the writer in the " American Geologist" for 

 1894, is equally heavy and of equal size, but differs from all the rest 



