434 CRETACEOUS PALEONTOLOGY. 



right just tO' its margin. Right valve with a deq> notch-like slit 

 on the anterior side just below the hinge, with a narrow, deep 

 groove running from it tOi the apex of the valve on the exterior 

 surface. Left valve provided with an internal fold, quite indis- 

 tinct except under a glass, on the anterior side of the beak, which 

 corresponds tO' the byssal notch of the right valve. Anterior 

 margin of the valve somewhat regularly rounded; basal margin 

 broadly rounded, and the posterior obliquely truncate, passing 

 backward slightly from the hinge extremity tO' the postero-basal 

 line. Surface of the valves smooth or very finely lamellose, and 

 marked with concentric undulse. When not at all worn or mace- 

 rated the surface of the left valve shows indistinct thread-like, 

 interrupted, radiating lines which remind one very strongly of 

 those seen on species of Placunomya." (Whitfield). 



The dimensions of the right valve illustrated by Whitfield are :. 

 length, 14.5 mm.; height, 12 mm. 



Remarks. — This species has been met with but rarely in the 

 recent collections of the Survey. 



Formation and locality. — Navesink marl, near Holmdel 

 (128^), near Freehold (WTiitfield). 



Geographic distribution. — New Jersey. 



Saper-family OSTRACEA. 

 Family OSTRBIDAE. 



Genus OstrEa Linneus. 



Ostrea cretacea Morton. 



Plate XLIL, Fig. 11. 



1834. Ostrea cretacea Mort., Synop. Org. Rem. Cret. Gr. U. S.^ 



p. 52, pi. 19, fig. 3. 

 i860. Ostrea cretacea Owen, 2d Rep. Geol. Recon. Ark., pi. 7, 



fig- 7- 

 1861. Ostrea cretacea Gabb, Proc. Acad. Nat. Sci. Phil., 1861, 



p. 328. 

 1861. Ostrea cretacea Gabb, Synop. Moll. Cret. Form., p. 20S 



(152). 



