52 PALEONTOLOGY OF OHIO. 



obtuse points occur between that and the ends. These may belong to 

 another species, but the material at hand does not justify us in separating 

 them from the forms which have been found at the West. 



Orodus elegantulus occurs in Illinois, in the Burlington limestone. 



Ctenoptychitts semicieculaeis. N. and "W". 



Plate LVIIL, Fig. 14. 



A single tooth of this species was found in a Coal Measure limestone, 

 Adams Township, Muskingum County, O., by Professor J. J. Stevenson. 

 It is rather less arched than most specimens of the species, but, in other 

 respects, is undistinguishable from many which I have from the Coal 

 Measures of Indiana and Illinois. 



Teeth generically identical with these, and with difficulty distinguish- 

 able specifically, are common in the Carboniferous limestone of Armagh, 

 Ireland. These have not yet been described, but were named by Agassiz 

 Ctenoptyehius dentatus. He subsequently referred them, in his MS. 

 ca;talogues, to the genus Harpacodus, created to receive them ; still later 

 to a new genus, Pervpristis. The latter name has been adopted by Mr. 

 O. St. John, who gives a definition of the genus in Dr. Hayden's " Final 

 Eeport on the Geology of Nebraska," p. 242. I find it impossible, how- 

 ever, to recognize more than specific differences between these teeth and 

 those which form Prof. Agassiz's tyjje species of Ctenoptyehius {Ct. ser- 

 ratus). 



From the Crinoidal limestone of the Lower Barren Measures, in the city 

 of Pittsburgh, I have a single tooth which is closely allied to, but distinct 

 from, those under consideration. In this specimen only a part of the crown 

 is shown. This is much flatter than that of Ct. semicircula/ris, the den- 

 ticles larger and symmetrically lance-shaped, and the whole surface covered 

 with a fine, crape-like wrinkling, instead of being highly polished, as it is 

 in the other specimens from America and Ireland. 



Pbtalodits Alleghanieh'Sis, Leidy. 



Plate LVni., Figs. 13, 13 a. 



The Crinoidal limestone, which is a very constant member of the Low- 

 er Barren Coal Measures of Ohio, has furnished so many fish teeth that it 

 deserves to be specified as one of the " fish beds " of the State. Most of 

 the fish remains of this horizon are small and usually imperfect shark's 



