NO. 2177. FOSSIL FISHES IN NATIONAL MUSEUM— EASTMAN. 251 



Ivind for the allocation of parts entering into the upper dental pave- 

 ment. The evidence referred to is furnished by a single large com- 

 pound plate, representing the fused members of the anterior pair of 

 mylostomid dental plates, found in the isolated condition, and origi- 

 nally described by Louis Hussakof ' in 1909 as the type of a dis- 

 tmct genus and species of Arthrodives. It has been suggested by 

 the present writer ^ that the new genus proposed by Doctor Hussakof, 

 and named by him DinognatJius, be maintained in a provisional sense. 



Fig. 5.— Dinognathus ferox (Hussakof). Cleveland Shale (Uppee Devootan), Lorain County, 

 Ohio. Reconstruction of the upper dental pavement. 



and that there should be associated with it, on theoretical grounds, 

 the unique mandible serving for the type of Newberry's species, 

 Mylostoma terreUi. 



A recent examination of the type material of both Mylostoma and 

 Dinognathus, now preserved m the American Museum of Natm-al 

 History, has satisfied the writer of the entire correctness of this view; 

 and in text-figure 5 is illustrated our conception of the arrangement 

 of the palatal dental elements of Dinognatlius. It is to be noted that in 

 this genus the anterior pair of palato-pterygoid dental plates is fused 

 into a single crushmg element. In DiniclitJiys, on the other hand, 

 the so-called "shear-tooth" is to be mterpreted as having arisen from 

 the fusion of the anteriorly and posteriorly placed elements on either 

 side of the upper jaw. 



•Hussakof, L. The sj'stematic relationships of certain American Arthrodires. Bull. Amer. Mus. Nat, 

 Hist., vol. 26, 1909, p. 268, flg. 5. 

 » Science, vol. 29, 1909, p. 997; Bull. Mus. Comp. Zoul., 1909, vol. 52, pp. 201-269. 



