MOLLUSCA. 443 



ventral margin the edge is folded into sharply angular teeth which 

 do not extend as plications into the body of the shell, these tooth- 

 like crenulations becoming smaller and at last disappearing upon 

 the lateral margins of the shell. Lower valve not known. 



Remarks. It is with some hesitation that a species of so 

 variable a group of shells as the oysters has been proposed for a 

 single specimen, but it has not been possible to identify it with 

 any of the described forms, and it seems to be so distinct that it 

 is probable that additional examples, should they be found, could 

 be recognized without difficulty. The shell has much the general 

 outline of the specimen referred to O. crenulimarginata by Whit- 

 field, but that shell entirely lacks the characteristic denticulation 

 of the ventral margin of this species. 



Formation and locality. Navesink marl, near Crawfords Cor- 

 ner (I26 7 ). 



Geographic distribution. New Jersey. 



Ostrea tecticosta Gabb. 

 Plate XLIII, Figs. 17-19. 



1860. Ostrea tecticosta Gabb, Jour. Acad. Nat. Sci. Phil., 2nd 



ser., vol. 4, p. 403, pi. 68, figs. 47-48. 



1861. Ostrea tecticosta Gabb, Synop. Moll. Cret. Form., p. 210 



(154). 



1864. Ostrea tecticosta Meek, Check List Inv. Foss. N. A., 

 .Cret. and Jur., p. 6. 



1868. Ostrea tecticosta Con., Cook's Geol. N. J., p. 724. 



1869, Ostrea tecticosta Coquand, Monog. Gen. Ostrea Terr. 



Cret, p. 50, pi. 17, figs. 10-11. 

 1876. Ostr,ea pmilla Gabb, Proc. Acad. Nat. Sci. Phil. (1876), 



,p. 321. 

 1884. Ostrea tecticvstata White, 4th Ann. Rep. U. S. G. $., p. 



301, pi. 17. 

 1886. Ostrea tecticosta Whitf., Pal. N. J., vol. i (Monog. U. S. 



G. S., vol. 9), p. 33, pi. 3, figs. 1-2. 

 1905. Ostrea tecticosta Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 10. 



