Description of new PalceoBoic Fishes. 189 



point and the symphysis. A broad roughened depression or pit at the sym- 

 physis marks the place of attachment of a strong ligament, which united the 

 mandibles, and prevented the splitting of the forked extremity of the jaw. 



Only the anterior half of the mandible of this remarkable 

 fish has yet been found. We therefore have but an imperfect 

 knowledge of its structure and relations. It is evident, how- 

 ever, that it was allied to Dinichthys, since the general form 

 of the mandible is similar; the posterior extremity was 

 doubtless flattened and spatulate, the anterior third exposed, 

 and this portion is thickened, and forms a segment of a circle 

 by its lower outline,, as in Dinichthys. The turned up ex- 

 tremities of the mandibles in Dinichthys are also divergent; 

 and we have only to imagine the rows of teeth, which are set 

 along the upper margin of the mandibles of D. Hertzeri, con- 

 tinued down the inner margins of the divergent extremities, to 

 produce Diplognathns. A fragment of the mandible of 

 Diplogmathus, carrying a few teeth, was found some years 

 ago, imbedded in the Huron shale at Sheffield, Ohio. This had 

 evidently been broken from the jaw by violence, and is per- 

 haps the record of an unequal coutest between Dij>lognathus 

 and Dinichthys. This fragment was referred to Dinichthys 

 Hertzeri, and was regarded as evidence of the existence of 

 that species, associated with D. Terrelli, in the last epoch of 

 the Devonian age ; but we now know that this reference was 

 an error ; and all the facts seem to indicate what was believed 

 before the discovery of this fragment, that Dinichthys Hert- 

 zeri lived only in the earlier part of the Huron epoch, and 

 that it was replaced, through modification or otherwise, by 

 the D. Terrelli in the last portion of the period during which 

 the Huron shale was being deposited. 



From the Huron Shale, Sheffield, Loraine Co., Ohio. 



Discovered by Mr. Jay Terrell. 



Glyptopomtts Sayrei. (n. sp.) 



Fish fusiform, about two feet in length by five inches in diameter; head 

 triangular in outline, five inches in length and breadth, cranial plates un~ 

 known. Under side of head covered with two large sigmoidally elliptical 



