78 CRETACEOUS AND TERTIARY FISH. 



the kidney-shaped head of Sphyrna tiburo. The fossils are only 

 known from detached teeth, which seem to be largely doubtfully 

 located in this genus, owing to their close resemblance to those 

 of Bulamia, and are referred to six species. 



Sphyrna gibbesii Hay. 



Teeth compressed, triangular and moderately thick. Crown 

 moderately large, compressed, sharp-pointed, its base width about 

 one-half its height, outer face flattened and inner evenly convex, 

 surfaces smooth. Apex slightly deflected. Cutting-edges entire. 

 At base of crown 3 or 4 broad-pointed cusps, graduated down 

 externally till outer are quite small. Edges of cusps entire, 

 though trenchant. Root rather wide, moderately thick, inner 

 surface flattened or slightly concave, and outer surface moder- 

 ately swollen convexly. Lower edge of root a little emarginate. 

 Length 8 mm. 



Fig. 37. — Sphyrna gibbesii Hay. Monmouth Co. (Knieskern). 



My examples seem to be this species, which appears to be char- 

 acterized by its small size, entire cutting-edge and enlarged basal 

 cusps. They agree largely with Gibbes' figure of Sphyrna den- 

 ticulate. The species has not before been recorded from New 

 Jersey. 



Formation and locality. I have six teeth from Monmouth 

 County (P. D. Knieskern). These are without definite indica- 

 tion as to which of the Cretaceous beds they were found in, but 

 presumably the upper would be correct. 



Sphyrna prisca Agassiz. 



Zygcena prisca Cope, Proc. Amer. Philos. Soc. Phila., XIV, 1875, p. 362. 

 (Cumberland Co. Miocene.) 



Lateral teeth well compressed, with broad base, triangular. 

 Crown small, narrowly triangular, compressed somewhat 

 smooth, outer surface flattened and inner surface evenly convex. 



