72 NEW YORK STATE MUSEUM 



being referred to as " section H " and photographed in plate 4 of Grabau's 

 Geology and Palaeontology of Eighteen-Mile Creek.' The specimen in ques- 

 tion is excellently preserved, measures 3 cm. in length, and lacks only the 

 extreme tip of the symphysial beak. A single large dental plate, appar- 

 ently referable to this species, has also been obtained by Dr John M. 

 Clarke from the Goniatite or Parrish limestone (Portage) near Naples, 

 N. Y. 



Formation and locality. Middle Devonic of Iowa, Illinois, Missouri, 

 Wisconsin and Manitoba. l^pper Devonic of Iowa and Elmhurst, 111. 

 Genesee shale of Eighteen Mile creek, and Portage of Naples, N. Y. 



Ptyctodus compressus Eastman 



1898 Ptyctodus compressus C. R. Eastman. Am. Nat. 32 : 479, fig. 18-27 

 The tritors in this species are relatively longer and narrower than in 

 the preceding, and the oral margin in advance of the triturating surface is 

 developed into a long, sharp cutting edge. In all other species this trench- 

 ant margin is shorter than the tritoral area, but in the present form it is 

 invariably longer, sometimes exceeding the length of the tritor by one 

 fourth. The dental plates are as a rule less curved than those of P. 

 c a 1 c e o 1 u s, and the symphysial beak less produced. 



Formation and locality. State Quarry beds (Upper Devonic) ; North 

 Liberty, Johnson county, la. 



Ptyctodus ferox Eastman 



1898 Ptyctodus ferox C. R. Eastman. Am. Nat. 32: 480, fig. 35-40 



1899 Ptyctodus ferox C. R. Eastman. Jcjur. (leol. 7: 282 



Dental plates unusually large and massive, attaining a total length of 

 about 14 cm, and exhibiting but slight lateral curvature. Lower dental 

 plate with a stout symphysial beak, the front margin projecting downward 

 into a long spiniform process, evidently for strengthening the symphysial 

 union. Anterior margin of upper dental plate uniformly rounded, not pro- 

 duced into a beak or spiniform process, and showing on the outer face 

 ' Buffalo Soc. Nat. Sci. Bui. 1898. 6: 5. 



