3 o CRETACEOUS AND TERTIARY FISH. 



minute behind eye. First dorsal above or after ventral, second 

 opposite and somewhat before anal. Tail most abruptly bent up 

 at base. 



Large sharks of warm seas, referred to two genera. 



Genus GINGLYMOSTOMA Miiller and Henle. 



Ginglymo stoma Miiller and Henle, Arch. Naturg., 1837, p. 396. (No species 



given.) Type Squalus cirratus Gmelin, virtually designated by Bonaparte, 



Nuov. An. Soc. Nat. Bologna, II, 1838, p. 212. 

 Plicodus Winkler, Arch. Mus. Teyler, III, 1874, p. 301. Type Plicodus 



thielensis Winkler, monotypic. 

 Acrodobatis Leidy, Journ. Acad. Nat. Sci. Phila., (2) VIII, 1877, p. 250. 



Type Acrodobatis serra Leidy, first species, designated by Hay, Bull. U. 



S. Geol. Surv., No. 179, 1902, p. 310. 

 Acrodontobatis Leidy, 1. c, nom. orig. 



Many series of teeth in jaws, each with a strong median cusp 

 and one or two small basal cusps each side. Second dorsal nearly 

 opposite anal. Tail about one-half rest of body. 



About seven extinct and two existing species are known. 



GINGLYMOSTOMA OBLIQUUM (Leidy). 



Acrodobatis obliquum Leidy, Journ. Acad. Nat. Sci. Phila., (2) VIII, 1877, 

 p. 250, PI. 34, fig. 14. Marl of Monmouth Co., N. J. 



Crown wider than high and base extended downward at mid- 

 dle in a rounded prominence, and backward posteriorly in a 

 similar prominence. Summit arises in a tapering point, and 

 lateral acute borders show seven denticles successively decreasing 

 in size. Outer side presents two larger denticles succeeded by 



Fig. 4. — Ginglymostoma obliquum (Leidy). (From Leidy.) 



four minute ones. Inner acute border of crown long, convex in 

 its course from base of main point. Length 7 mm. (From 

 Leidy.) 



