126 THE DEVONIAN OF MISSOURI. 



long. One specimen of cephalon is exfoliated enough to show one groove on the glabella. 

 The identification of the Mineola specimens is fairly satisfactory but one poorly pre- 

 served pygidium from the Snyder Creek shale is much less certain and it is even probable 

 that it belongs to another genus. The only specimen collected from the Snyder Creek 

 is from the locality near the mouth of Cow Creek about seven miles east of Fulton. 



VERTEBRATA 



Class PISCES 

 Subclass Holocephali 

 Order Chimaeroidei 



Family Ptyctodontidae • 



Genus Ptyctodus Pander 

 Ptyctodus calceolus (Newberry and Worthen) 

 Plate 31, figures 1 and 2 



1866. Rinodus calceolus Newberry and Worthen. Rept. Geol Surv. Illinois, 2, pp. 



106-107, pi. 10, fig. 10. 

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



274. 

 1875. Ptyctodus calceolus Newberry, Rept. Geol Surv. Ohio, II, Pal. pt. 2, p. 59, pi. 



59, figs. 13 and 13a. 



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



1898. Ptyctodus calceolus Eastman, Rept. Geol. Surv. Iowa, VII, p. 115, text-fig. 10a. 



1898. Ptyctodus calceolus Eastman. Amer. Nat. 32. pp. 476-479, figs. 1-17. 



1899. Ptyctodus calceolus Weller, Jour. Geol., 7, pp. 484-485. 



1906. Ptyctodus sp., Dean, Carnegie Inst. Wash. Pub. No. 32, p. 137, text-fig. 116. 



1906. Ptychtodus cal.eolus Norton, Rept. Geol Surv. Iowa (1905), XVI, p. 356. 



1907. Ptyctodus calceolus Eastman, Mem. N. Y. State Mus. 10, pp. 71-72. 



1908. Ptyctodus calceolus Eastman, Iowa Geol. Survey, vol. XVIII, pp. 133-135, 

 PI. V, figs. 1-17. 



1911. Ptyctodus calceolus Cleland, Wisconsin Geol. Surv. Bull. -21, p. 150, pi. 48, figs. 



1-17. 

 1914. Ptyctodus calceolus Branson, Devonian Fishes of Mo., Univ. Mo. Bull., Science 



Series, vol. 2, pp. 64-65, pi. 3, figs. 3 and 4. 

 1918. Ptyctodys calceolus Branson, Geology of Missouri, pi. IV, fig. 16. 



Eastman's description — "Dental plates compressed into a thin cutting edge shortly 

 behind the symphysis, but widening gradually, becoming more or less outwardly curved, 

 and the functional surface occupied for nearly its entire width by the tritorial area, the 

 inner margin of which is more strongly curved than- the external. Laminar structure 

 of the tritors indicated superficially by fine punctae arranged in parallel rows which 

 are directed obliquely across the triturating surface. The compressed edge in advance 

 of the tritor in the lower dental plate slopes rapidly upward and terminates in a strong 

 anterior beak, beneath which the front margin is continued downwards in a short, blunt 

 process. Upper dental plates similar in a general way to the lower, except that the 

 symphysial margin is rounded and not produced into a beak." 



Remarks — This species is so highly variable that it has the appearance of a scrap 

 heap for specimens that cannot be referred elsewhere. The specimens from the Mis- 

 souri Devonian accentuate this aspect. The varieties are so pronounced that some 

 should probably be described as new species. However, the material is so fragmentary 



