DEVONIC FISHES OF THE NEW YORK FORMATIONS I 33 



that the Arthrodiran skull was constructed upon essentially the same model 

 as in Neoceratodus ; and the latter, accordingly, furnishes a most valuable 

 criterion for interpreting structural details of the former. 



Formation and locality. The remains of this species occur abundantly 

 in the Hydraulic limestone of Milwaukee, Wis., and are not uncommon in 

 the Mesodevonic limestone of Iowa and Illinois. Characteristic fragments 

 have been found in the Black slate (= New Albany, equivalent to the 

 Genesee) near Lexington, Ky. ; and portions of the dentition, including 

 more than one well preserved mandible, have been obtained from the 

 Oneonta beds (Senecan) near Delphi and Oxford, N. Y. 



Dinichthys newberryi Clarke 



Plate 6, figure 2 



1885 Dinichthys newberryi J. M. Clarke. U. S. Geol. Sur. Bui. 16, p. 17, 



pi. I, fig. I 

 1889 Dinichthys newberryi J. S. Newberry. U. S. Geol. Sur. Monogr. 16: 153 

 1897 Dinichthys newberryi C. R. Eastman. Mus. Comp. Zool. Bui. 31:30, 



pi. I, fig 2 

 1906 Dinichthys newberryi L. Hussakof. Am. Mus. Nat. Hist. Mem. 9, p. 145 



Mandibles attaining a total length of 28^ cm in the type specimen, 

 with very prominent anterior beak, simple trenchant margin, and closely 

 resembling that of D. pustulosus in general outline. There are, how- 

 ever, no denticulations or tubercles along the downward slope immediately 

 behind the cutting margin, and the other plates associated with the type 

 specimen have a smooth external surface. 



A single dorsomedian plate from the same horizon as the type, and 



considered by Dr Clarke to be specifically identical with it, is thus described 



by him : 



In the same Styliola layer as it outcrops on the east side of Canan- 

 daigua lake, near Genundewah, 6 miles from the Bristol locality, I had 

 earlier discovered a dorsomedian plate belonging presumably to the same 

 species. Its dimensions are as follows: length, 12^ cm (broken); width 

 anteriorly, 13^ cm ; hight of carinal process, 5 cm. . . . The posterior edge 

 of this plate in D. newberryi is broken and has apparently lost 3 or 4 

 cm from its length. The smallness of the bones of D. newberryi does 



