DEVONIAN FISHES OF IOWA 133 



Genus ptyctodus Pander. 



Oral surface triturating, the single tritoral area of each dental 

 plate well differentiated, and consisting of hard, punctate, super- 

 imposed laminae arranged more or less obliquely to the func- 

 tional surface. Lower dental plates with upturned syinphysial 

 beaks, which, as shown by marks of wear, closed against the 

 outer margin of the upper dental plates. Anterior margin of 

 lower plates sometimes produced downwardly as a slightly re- 

 curved spiniform process. 



Ptyctodus punctatus Eastman. 

 (Plate III, Fig. 6) 

 1907. Ptyctodus punctatus C. E. Eastman, Mem. N. Y. State Mus. 10, p. 70. 



This species is readily distinguished from all others previously 

 described by the comparative coarseness and peculiar arrange- 

 ment of the medullary canals passing through the tritoral areas. 

 The sides and triturating surface of the latter are completely 

 covered by a network of small polygonal pittings, formed by the 

 termini of the medullary canals. As these are not grouped in 

 parallel lines, there is no surface indication of laminar struc- 

 ture. The simpler arrangement of the medullary canals in this 

 species, and the fact of its greater antiquity as compared with 

 other known species, are taken as indicating the primitive char- 

 acter of the present form. 



Formation and locality. Onondaga limestone (Ulsterian) ; 

 Le Eoy, New York, and corresponding formation in Ohio. 



Ptyctodus calceolus Newberry and Worthen. 

 (Plate V, Figs. 1-17) 



1866. Einodus calceolus Newberry & Worthen, Kept. Geol. Surv. Illinois, 2, 



p. 106, pi. 10, fig. 10. 

 1870. Ptyctodus calceolus Newberry & Worthen, Rept. Geol. Surv. Illinois, 4, 



p. 374. 

 1875. Ptyctodus calceolus J S. Newberry, Rept. Geol. Surv. Ohio, Palreont. 



2, pt. 2, p. 59, pi. 59, fig. 13. 



1897. Ptyctodus calceolus S. Calvin, Proc. Iowa Acad. Sci. 4, p. 18. 



1898. Ptyctodus calceolus C. R. Eastman, Rept. Geol. Surv. Iowa, VII, p. 



115, text-fig. 10rt. 

 1898. Ptyctodus calceolus C. R. Eastman, Amer. Nat. 32, p. 476, figs. 1-17. 



