FOSSIL SQUALID^ OF THE UNITED STATES. 201 



Genus OXYRHINA, Agassiz. 



This genus is established on the character of the absence of lateral appendages in 

 teeth allied to Otodus. It is an important character in fossil genera and species, and 

 the distinction can only be doubtful when the base and root of the specimen are 

 imperfect, as there is then a difficulty in assigning it to Otodus, Lamna, or 

 Oxyrliina. 



Oxyrhina is generally known by its broad lanciform shape, differing from Lamria 

 which is always narrow and straight. The resemblance is greater between Otodus 

 and Oxyrhina — Otodus is generally larger, more triangular, thicker, and not so flat. 

 The root of Oxyrhina, particularly is less thick, and the branches less developed. In 

 other respects Oxyrhina approaches Lamna. 



1. O. HA.STALIS, Agassiz. Figs. 148 to 152. — The variety of form and dimensions 

 of these teeth, according to their position in the jaw, render their distinction difficult. 

 They are large, elongated and lanciform, the larger teeth mostly equilateral, probably 

 occupying the front ; others are more or less arched, very thin, not half as thick as 

 the breadth of the base of the enamel. The root is never as prominent as in Otodus, 

 and the terminal portions less developed. The inner face is regularly convex from 

 the base to the summit, and serves to distinguish this species from Ox. xiphodon, 

 which is more flat on this side. The base of the enamel is slightly sloped on the 

 outer face, and descends lower on the inner, and is more hollowed on that face. The 

 outer face is flat; on each side parallel to the edge is a vertical furrow, which extends 

 two-thirds or three-fourths of the height ; the middle is slightly prominent, with a 

 small depression near the base of the enamel. 



I have specimens from the Miocene of South Carolina, from T. W. Porcher, Esq., 

 from the Miocene of Virginia and Maryland, from J. G. Bruff, Esq., and F. Markoe, 

 Jr., and from the Eocene of South Carolina. 



2. O. XIPHODON, Agassiz. Figs. lo3, 154. — There is a single prominent character 

 which distinguishes this species from Ox. hasialis, viz., on the inner face, which is 

 ordinarily regularly rounded, at the base of the enamel, is a remarkable flattening, as 

 if ground ; unless this face be well preserved you cannot distinguish it ; usually 

 Ox. xiphodon is larger. All are curved outwardly at the summit. The base of the 

 enamel is almost the same on both sides, a little lower on the outer face. The root, 

 though a little thicker than the base of the crown, is still less developed than in other 

 species. On the outer face are parallel furrows next the edges, which give it an 

 undulated appearance. 



The specimens I have seen are all from the Eocene of South Carolina. 

 Agassiz now considers Ox. quadrans and Ox. retroflexa as forms of this species. 



