36 KANSAS UNIVERSITY QUARTERLY. 



of nearly equal size, small, slender, acute ; base narrow, prolonged 

 into a slender root at each extremity. 



Height of tooth 9 mm. 



Length of middle cusp 6 " 



Width of same at base 3 " 



Length of denticles 2 " 



One specimen. No. 11)49, U. S. National Museum, with the pre- 

 ceding species. 



LAMNID.E. 



The Lamnidpe comprise the largest and most voracious of the 

 sharks, represented by a number of species in the oceans of the pres- 

 ent time. They are elongated fishes, the dorsal fin without spine; 

 there is no nictitating membrane to the eye, and the gill openings are 

 wide. The teeth are solid in the adult, and are 300 or more in num- 

 ber. The teeth are found very commonly in the Cretaceous deposits 

 of Kansas, as elsewhere, usually scattered singly, though occasionally 

 found more or less connected by the calcified cartilage of the jaws in 

 several rows. Owing to the great variation of size and shape of the 

 teeth in the same individual, it is often difficult or impossible to cor- 

 rectly determine the forms. Doctor Eastman has recently figured and 

 described the nearly complete dentition of Oxyrhina mantelli, the 

 most common species of the family in Kansas. Doubtless similar 

 variations will be found in the different siDecies of the other genera 

 of this family. 



This genus difPers from Latnna only in the prevailing absence of 

 the lateral denticles of the teeth. The teeth are large. The genus 

 occurs from Jurassic to the present time. 



O-iyihlna mantelli. Plate XIII, figs. 41-46; plate XIV, figs. 2-2m. 



Oxijrhinn mrmtelU. (Geinitz) Agassiz, Poiss. Foss. III. 282, pi. XXXIII, ff. 

 i-5, 7-9 ; Eastman, Paleontographica, XLI, 149-192, pU. XVI-XVIII ( where 

 additional extensive synonymy will be found); Woodward, Proc. Geol. 

 Assoc. XIII, 196 — Cenomanian, Senonian and Turonian of Europe; Kan- 

 sas. Texas, New Jersey, Alabama, Colorado, etc. 



Oxijrhina extenta Leidy, Ext. Vert. Fauna, 302, pi. XVIII, ff. 21-25. 



"Moderate-sized, stout, three-cornered teeth; the crown on the 

 outer side nearly flat, with one or more vertical wrinkles; on the in- 

 ner side, lightly convex and smooth ; root long, thick, low, moder- 

 ately deeply furcate, usually obtuse at the ends, and on both sides 

 more or less flattened." Eastman, 1. c. 



This species is very common in the Kansas Niobrara, in fact, the 

 most common of all, and not infrequently it is represented by many 

 associated teeth. From the plates, and from Eastman's figures, it will 

 be readily identified in all its forms. 



