L88 Description of new Palceozoic Fishes. 



XIX. — Descriptions of new Palceozoie Fishes* 



BY J. S. NEWBEEEY. 

 Read April 9th, 1878. 



Diplognathus. Nov. G-en. 



Bones of cranium and body unknown. Dentary bones long and slender, 

 rising anteriorly into points which diverge from the symphysis, giving a 

 forked extremity to the lower jaw. Conical, incurved teeth, formed from 

 the jaw tissue, are set along the upper margin of their divergent, triangular 

 points. 



The remarkable structure of the jaw on which the forego- 

 ing description is based, is without parallel, so far as known, 

 in the animal kingdom. The dentary bones are produced 

 forward into triangular divergent points, which are set with 

 teeth on either margin ; thus the extremity of the lower jaw 

 forms a fork, set with strong recurved teeth. This would 

 form a very effective instrument for catching slender slippery 

 fishes like eels, and was doubtless used for that purpose. The 

 clanger of splitting this fork, which must have been considera- 

 ble, was obviated by a strong ligament which united the 

 mandibles at the symphysis. 



One species only is known, D. mirabilis, N., described 

 below. 



Diplognathus mikabilis. (n. sp.) 



Dentary bone of mandible about eighteen inches in length, by two inches 

 in width at the widest portion, anterior half thickened as in Dhuchthys, rising 

 into a prominent point anteriorly, which diverges from its fellow of the op- 

 posite dentary bone, to form a forked extremity to the under jaw. Upper 

 margin of the anterior half of the dentary bone set with strong, conical, 

 smooth, acute, incurved teeth, which diminish in size as they ascend the 

 elevated point. Foixr larger, conical, recurved teeth, are set on the inner 

 side of the triangular extremity of the mandible, filling the space between the 



*Ihe species characterized in this paper will be described more fully, and figured, in the 

 Report of the Geelogical Survey of Ohio. Vol. Ill, Palaeontology. 



