194 DR. GIBBES' MONOGRAPH OF THE 



the form of a solid triangle. The base of the crown is nearly horizontal, while that 

 of the root is notched in the middle. The root is moderately thick. 



My specimens from South Carolina are all from the Eocene. I have received 

 several from the Miocene of Maryland, from F. Markoe, Jr., and from the Miocene of 

 Virginia, from J. G. BrufF, Esq. Agassiz described specimens from the Miocene of 

 Europe, but mentions that count Munster had specimens from the chalk which he 

 thought similar. 



Genus GLYPHIS, Agassiz. 



The teeth of this genus are peculiarly formed. They are lanciform, with a thick 

 solid and expanded base. The body of the cone is awl-shaped and a little below the 

 point is wider, resembling a graver. The upper portion next the point is flat and 

 finely dentelated, while the lower part is free from serratures, and in some specimens 

 rounded. 



Agassiz describes a single species G. hastalis, from the London clay. 



G. suBULATA, Gibbes. Figs. 86, 87. — In this species the cone is shorter and 

 thicker proportionally than in G. hastalis, Agassiz, and is more straight, convex on. 

 both surfaces, more so on the inner ; the upper third of the outer face is flat, and the 

 point, which is compressed, has a tendency outward. A sharp lateral edge extends 

 from the apex equally on both sides two-thirds the length of the cone, and is finely 

 and uniformly indented. The root is thick ; the enamel extends lower on the outer 

 face and to the root on both. In the smallest specimen figured, the root is very 

 broad and not so thick, and the enamelled base has fine dentelures. 



The specimens figured are all I have met with, and are from the Eocene of South 

 Carolina.* 



Genus SPHYRNA, Rafinesgne. ZYG.ENA, Cuvier. 



The form of the hammer- headed sharks is very remarkable, but there is nothing as 

 peculiar in the character of their teeth by which they can be readily distinguished 

 when isolated, and they differ in the two jaws. 



The outer face is flat, and the inner prominent, the marginal indentations are very 

 minute, though often absent, especially in young and lower teeth. 



S. PRiscA, Agassiz. Figs, 88, 89, 90. — These are flat, thin, and triangular, sharp 

 pointed, the apex turned back ; the enamelled base extended equally on both sides 

 from the cone ; the serratures are very minute, in some specimens not visible to the 

 naked eye, and in others absent, except on the lateral basal extension. The root is 

 thick, flat on the outer, and convex on the inner side. 



* I have recently received several specimens from the Green Sand of New Jersey, presented by Mr, S. P. 

 Wetherill. 



