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ART. XIV. — Monograph of the Fossil Squalidcs of the Viiited States. By Robert 

 W. GiBBES, M. D., of South Carolina; Correspondent of the Academy of Natural 

 Sciences of Philadelphia, &c. 



(Continued from page 117.) 



Genus CARCHARIAS, Cuvier. 



This genus differs from Carcharodon, in the dentine presenting a hollow cone 

 internally, while it is solid in Carcharodon. 



I have seen only a single specimen from the United States of Carcharias tenuis, 

 from the Eocene S. C, too imperfect for description. Agassiz expresses some sur- 

 prise, that while the recent species are numerous, there are so few fossil. He met 

 with only two. 



Genus GALEOCERDO, Midler and Henle. 



This genus, separated from Galeus of Cuvier, comprises many species. In 

 Gahus the teeth are smooth on the anterior edge, and have few dentelures on the 

 posterior — in Galeocerdo they are crenated on the whole extent, but rather 

 unequally — the base particularly has large notches, while the point has but fine 

 indentations. Agassiz had found specimens so uniform in the indentations of the 

 whole contour, that he constituted a genus based on this character, which he called 

 CoRAX. I have his authority for the reunion of it with Galeocerdo, since he has 

 seen many other specimeiis. 



In Galeocerdo the teeth are equal in both jaws — nearly as deep as long — the 

 anterior edge is regularly arched, the posterior strongly notched, and below the notch 

 are the largest crenatures. The outer face is flat, the inner more or less elevated ; 

 the root is not very thick, generally concave and parallel to the base of the crown. 

 Of the species given by Agassiz four are from the chalk, and three from the tertiary. 



1. G. aduncus, Agassiz. Figs. 54, 55, 56, 57, 58. — This species is usually about 

 a half inch in length and the same in height — occasionally longer — the anterior edge 

 is a regular arch finely indented, the posterior angulated, more or less obtuse ; below 

 the angle the dentelures are well marked, but are scarcely visible above. The base 

 of the enamel is less sloped on the outer than on the inner face, where it forms almost 

 a right angle. The root is more or less concave and moderately thick, as in all 

 Galeocerdos. Agassiz's specimens are from the Miocene of Europe — mine from the 

 Eocene of South Carolina. 



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