MOLLUSCA. 439 



Formation and locality. Marshalltown clay-marl, near 

 Swedesboro (180). 



Geographic distribution. New Jersey, Delaware, Alabama, 

 Tennessee. 



Ostrea plumosa Morton. 

 Plate XLIL, Figs. 16-18. 



1833. Ostrea plumosa Mort., Am. Jour. Sci., ist ser., vol. 23, 



P- 293. 



1834. Ostrea plumosa Mort., Synop. Org. Rem. Cret. Gr. U. 



S-, P- 5i, PL 3, % 9- 

 1 86 1. Ostrea plumosa Gabb, Synop. Moll. Cret. Form., p. 209 



(153). 



1864. Ostrea plumosa Meek, Check List Inv. Foss. N. A., Cret. 

 and Jur., p. 6. 



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



1869. Ostrea plumosa Coquand, Mo-nog. Gen. Ostrea Terr. 



Cret., p. 61, pi. 32, fig. 9. 

 1876. Ostrea plumosa Gabb, Proc. Acad. Nat. Sci. Phil. 



(1876), p. 320. 

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



299, PL 37, figs. 5-6. 

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



G. S., vol. 9), p. 31, pi. 3, figs. 12-13. 

 1886. Anomia argentaria Whitf., Pal. N. J., vol. I (Monog. U. 



S. G. S., vol. 9), pi. 4, fig. 9 (not figs. 10-11). 

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



(1905), p. 10. 



Description. "Shell small, ovate, ovate-triangular or elon- 

 gate-spatulate, thin and, somewhat fragile irregularly convex on 

 the upper valve, often subangulated longitudinally, either along 

 one side or the other, beak of the upper valve thin, sharp and 

 pointed ; the ligamental area small and inconspicuous in most 

 cases, though sometimes of moderate size. Exterior of the upper 

 valve marked by obscure plications in all the type specimens, 

 which cross the valve obliquely in either direction from right to 



