no CRETACEOUS AND TERTIARY FISH. 



the evidence of detached teeth, and, by a misunderstanding of the 

 generic characters, the majority of the American forms have 

 hitherto been ascribed to Ischyodus. Most of the type specimens 

 of the latter are in the collection of Prof. E. D. Cope, Philadel- 

 phia, where the present writer has had the privilege of examin- 

 ing them, and many of the specific distinctions cited in the 

 diagnoses would be regarded as varietal in Britain." However, 

 the present writer seems justified in following the views of Hus- 

 sakof, who has studied these specimens now in the American 

 Museum of Natural History in New York City. 



Genus EDAPHODON Buckland. 



Edaphodon Agassiz 1 , Poiss. Foss., Ill, 1843, p. 351. Type Bdaphodon buck- 

 landi Agassiz, restricted by Woodward, Cat. Foss. Fishes, II, 1891, p. 80. 



Bdaphodus, auct. 



Passalodon Buckland, Proc. Geol. Soc. London, II, 1838, p. 687. No de- 

 scription or species. 



Psittacodon Agassiz, Poiss. Foss., Ill, 1843, pp. 340, 348. Type Chimcera 

 mantellii Agassiz, virtually designated, first species. 



Dipristis Marsh, Proc. Amer. Assoc. Adv. Sci., 1869, p. 230. Type Dipristis 

 miersii Marsh, monotypic. (Not of Gervais.) 



Eumylodus Leidy, Rep. U. S. Geol. Surv. Terr., I, 1873, p. 309. Type 

 Eumylodus laqueatus Leidy, monotypic. 



Diphrissa Cope, Proc. Acad. Nat. Sci. Phila., 1875 (Feb. 9th) 2 , (2) p. 19. 

 Type Ischyodus solidulus Cope, designated, monotypic. 



Mandibular tooth massive, with no definite thickening on 

 outer aspect, symphyseal facette very broad. Anterior tritor 1, 

 sometimes smaller one below. Median tritor 1, occasionally di- 

 vided longitudinally. External tritors 2. Palantine teeth robust, 

 no well-defined thickening on outer aspect, and three tritors as 

 two inner and one outer. Vomerine teeth mostly triangular in side 

 view, tritors on oral edge. Postoral region laterally expanded, 

 without any thickening. 



The species, about 26, are all extinct. 



1 Buckland, Proc. Geol. Soc. Lond., II, 1838, p. 687. Descr. imperfect, no 

 species given. 



2 Issued April 20th, 1875. 



