MARYLAND GEOLOGICAL SURVEY 91 



The anterior teeth (Plate XXXII, Fig. 13) are stout and narrow, 

 convex on both faces, between 3 and 4 cm. in total height, and with 

 fewer and more irregular serrations than the lateral teeth. Many of 

 these piercing teeth have the serrations reduced to slender cusps, more 

 or less separated, and confined ^arincipally to the basal portion of the 

 crown. The latter are obviously of different nature and origin from 

 lateral denticles, properly so called, being merely retrogressive modifi- 

 cations of the cutting edge, and hence only of secondary importance, 

 whereas lateral denticles represent the serial multiplication of entire 

 crowns. Worn specimens of the anterior teeth are readily distinguished 

 from Lamiui and other forms by the pronounced swelling on the inner 

 face of the root. 



A large series of teeth has been collected from Charles county and 

 other well-known Miocene localities in this and adjoining states. As 

 is true also of Oxyrliina desorii and Carcharudon megalodon, the Eocene 

 examples from South Carolina seem to have attained a somewhat larger 

 size than their Miocene successors. 



Occurrence. — Calvert Formation. Plum Point, Fairhaven, Popes 

 Creek, Charles county near the Patuxeut river. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Philadeli^hia Academy of Xatural Sciences. 



Genus SPHYRNA Rafinesque. 



Sphyrna peisca Agassiz. 

 Plate XXXII, Fig. 15. 



Sphyrna prisca Agassiz, 1843, Poiss. Foss., vol. iii, p. 33-4, pi. xxvi a, figs. 35-50. 

 Sphyrna denticulata Emmons, 1858, Kept. N. Car. Geol. Survey, p. 241, lig. 84rt. 

 Sphyrna prisca Eastman, 1901, Md. Geol. Survey, Eocene, p. 110, pi. xiv, fig. 7. 



The small, pointed and finely serrated teeth of this " Hammerhead 

 shark " are met with quite frequently in the principal Miocene locali- 

 ties of this and adjoining states. It is very abundant in the Eocene of 

 South Carolina, but the specimens figured under this name by Gibbes ' 

 have the appearance of belonging to Carchorias rather than to Sphyrna. 

 Only two or three teeth of this species have been obtained from the 

 Eocene of Maryland. 



1 Jour. Acad. Nat. Sci. PhiLa., 3nd ser., vol. i, 1849, pi. xxv, figs. 88-90. 



