FOSSIL SQUALID^ OF THE UNITED STATES. 199 



importance, especially in fossil species. The species are in genera] less in size than 

 Carcharodon, and the largest are seldom as large as the smallest of them. 



It is more difficidt to distinguish Otndiis from Oxijrhina; it has the same broad flat 

 form, smooth at the edges, but Otodus is specially characterized by the presence of a 

 lateral denticle on each side, usually equal ; often it is rounded, sometimes 

 compressed and sharp, rarely angular or indented. Lamna and Odontaspis have it, 

 but always smaller, cylindrical, and more pointed and lanciform. The root is largely 

 developed, very deep and thick, but has no elongated branches as Lamna. When 

 the root and lateral denticles are detached, it is hard to distinguish Lamna from 

 Otodus and Ozyrhina. Agassiz describes several species as of doubtful o-enus on this 

 account. 



1. O. OBLiQUUs. Figs. 131 to 137. — This species is common in New Jersey, whence 

 there are fine specimens in the Cabinet of the Academy. I have casts also of several 

 from Mr. C. Barclay, of Troy, from the Eocene of New Jersey. 1 have no specimen 

 of 0. obliquus from South Carolina. 



It is massive, with a well developed root, .so large that in some the depth equals 

 more than half the height of the crown. The outer face is nearly flat, grooved 

 longitudinally in the middle at the base of the enamel, the inner surface is very 

 prominent, viewed en projil the root seems deeper on the inner face, where is a space 

 deprived of enamel ; below this the root is thickest. The lateral appendages are 

 thick and irregular, more developed in arched than in upright teeth. Agassiz thinks 

 the presence of the lateral denticles not important for species, but much so for the 

 genus. 



The prominent character of Olodus obliquus is its mas.sive size and preponderance 

 of root. The enamel is dense and very full at the base of the crown. The species 

 described as Otodus lanceolatus, by Agassiz, he thinks most probably belongs to O, 

 obliquus. 



2. O. APPENDicuLATUS, Agassiz. Figs. 138, 139, 140. — Distinguished by large 

 lateral denticles, compressed and usually obtuse, but some are very sharp. The root 

 is not large, and thinner, and not so deep as that in O. obliquus ; base of the crown 

 nearly horizontal. The root is absent in two of my specimens, which are from the 

 Green Sand of New Jersey. 



3. 0. LEVIS, Gibbes. Fig. 141. — The tooth here figured I published* as new, and 

 upon reference to the figures given by Agassiz, I find he has one resembling it, (Fig. 

 7, Tab. 32,) which he doubted about separating from 0. appendiculatus. The 

 following is my description : 



* Proceedings of Academy, September, 1847. 

 51 



