DEVONIAN FISHES OF IOWA 135 



this species, some of considerable size, are occasionally found 

 in the New Albany ( = Genesee) Black Shale near Louisville, 

 Kentucky, and more rarely in the Genesee of western New York 

 State. At least one instance is reported of its occurrence in 

 the Portage fauna of the Agoniatite or Parrish limestone near 

 Naples, New York. Its accompaniment by fin-spines of the form 

 described as Heteracanthus, and other detached structures, is 

 noted below. 



Formation and locality. Middle Devonian of Iowa, Illinois, 

 Missouri, Wisconsin and Manitoba. Upper Devonian of Iowa 

 and Elmhurst, Illinois. Genesee of Louisville, Kentucky, and 

 near Buffalo, New York. Portage beds of Naples, New York. 



Ptyctodus compressus Eastman. 



(Plate V, Figs. 18-27) 



1898. Ptyctodus compressus C. R. Eastman, Amer. Nat. 32, p. 479, text-figs. 

 18-27. 



The tritors of this species are relatively longer and narrower 

 than in the preceding, and the oral margin in advance of the tri- 

 turating surface is developed into a long, keen trenchant edge. 

 In all other species this sectorial margin is shorter than the tri- 

 toral area, but in the present form it is invariably longer, some- 

 times even as much as one-fourth longer than the tritor. The 

 dental plates are as a rule less curved than those of P. calceolus, 

 and the symphysial beak of the lower elements is less produced. 



Formation and locality. State Quarry beds (Upper De- 

 vonian) ; North Liberty, Johnson county, Iowa. 



Ptyctodus ferox Eastman. 

 (Text-figures 20-22) 



1898. Ptyctodus ferox C. E. Eastman, Amer. Nat. 32, p. 480, text-figs. 35-40. 



1899. Ptyctodus ferox C. E. Eastman, Journ. Geol. 7, p. 282. 



1906. Ptyctodus sp. B. Dean, Carnegie Inst. Wash. Pub. no. 32, p. 139, text- 



fig. 126. 



1907. Ptyctodus ferox C. B. Eastman, Mem. N. Y. State Mus. 10, p. 72. 



Dental plates unusually large and massive, attaining a total 

 length of about 14 cm, and exhibiting but slight lateral curva- 

 ture. Lower dental plates with stout symphysial beak, the front 



