119 
P. Pusi0. Lam. 55.—F. p. 385.—Turt. p. 215. ¢. 
17. f. 2—Ostrea P. Lin. 1146.?—D. p. 261.—-Ch. 
Ff. 635,6.— Knorr. 4. t. 12. f. 2.—Oblong-oval, equi- 
valve, with about forty rounded and nearly smooth 
striee, which are usually alternately larger and smaller, 
and very slightly muricated about the margin ; variable 
in coloring, often brownish white with chocolate ziczac 
bands, or saffron or crimson, the under valve generally 
pure white. 3...8. Torbay, in rocks. 
P. Istanpicus. Turt. B. p. 216.—F. p, 385,— 
Inst. t. 1057. f. 4.—Ribs numerous, rough, unequal, 
from seventy to one hundred, grouped in pairs or other- 
wise, reddish, the furrows reticulated. 3...34. W. 
Scotland, rare. 
TRriBE.—OSTRACEA. 
Ligament internal or semi-internal; shell irregular 
and of a foliated texture. 
Grenus.—OSTREA. 
Fized, inequivalve, irregular, with the beaks more or 
less separated from each other and becoming unequal 
by age; hinge toothless, with a cavity which is 
partly external and in the lower valve becomes elon- 
gated ; ligament internal 
