TRIBE OSTRACEA. 301 
the upper valve usually white, margined by the dark external lamelle. 
Cartilage-plate very large, the adjacent margins denticulated: scar 
ample. 33. ‘ America.”' The bumps so often found upon this 
species result from tts habitat. 
O. Marearitacea. Lam. 26.—E. t. 181, f. 1, 2, 3.—BIl. t. 59, 
F. 5.—Desh. FE. 2, p. 295. Ovate-acute, thick, recurved, beaked and 
bag-shaped, white, clouded with rose or purple. Upper valve flat, 
somewhat lamellated, the lamellz depressed, the surface beneath them 
pearly. Beak nearly flat, cartilage-canal scarcely concave. 44. 
S. America? ‘ Resembles Cornucovia, but is not at all plicated.” 
O. Gipposa. Lam. 27.—E. t. 182, f. 3, 4, 5.  Ovate-oblong, 
distorted, gibbous near the beaks, tinged with violet, lamellated : lower 
valve bag-shaped: inner margin denticulated. 24. Hab.? 
O. Exuiprica. Lam. 29.—Del. t. 17, f. 2.—Ch. 8, f. 661 (well). 
Oval or oboval, thin, subequivalve, more or less compressed, never 
beaked, nearly equally broad at each extremity, white tinged with 
purple, rayed with darker lines. Surface of the upper valve glabrous, 
not lamellar. Ventral margin more or less arched: edges not much 
indented. Inside silvery white, sometimes iridescent; the upper 
valve with a few granules, which at times are nearly obsolete, near 
the cartilage, whose receptacle is wide but short. 2}. Hab. ?? 
O. Aneutata. W, S. t. 2, f. 8—Conch. Mis. O. f. 10, 11.— 
GrypH#A AnGuLata, Lam.—Del. t. 20, f. 3—Crouch, t. 12, f. 7. 
Oval, arcuated at the base, tolerably strong, very imequivalve; the 
beaks greatly incurved and subspiral. Upper valve shallow, dirty 
white, with a few radiating linear purplish markings, with close-set 
imbricated membranaceous concentric flakes, which are not at all 
curly, but greatly depressed ; lower valve profound, usually affixed at 
1 According to the tablets at the French Museum, it forms but 
one species with TuBERcuLATA and AUSTRALIS. 
O. Tupercutata. Lam. 24.—Ann. du Mus. 4, t. 67, f. 2. Ovate 
wedge-shaped, whitish, slightly tinged with violet. Upper valve 
flattish; lower valve bag-shaped, beaked, armed with depressed 
semiglobose bubble-like tubercles, which are ragged at the margin. 
Timor. 
O. Ausrratis. Lam. 28. Ovate, lamellar, not folded, dilated at 
the ventral margin, retuse, violet, especially within ; lower valve bag- 
shaped: inner edge denticulated. 23. New Holland. 
2 O. HaxrororpEa (Lam. 80), O. Drerormis (Lam. 31) and O. 
Fucorum (Lam. 32) must be expunged; the characteristics of the 
first being accidental, not essential, and the two last bemg merely 
the fry of some larger species. 
