TRIBE OSTRACEA. 



301 



the upper valve usually white, margined by the dark external lamellae. 

 Cartilage-plate very large, the adjacent margins denticulated: scar 

 ample. 3£. "America." 1 The bumps so often found upon this 

 species result from its habitat. 



O. Margaritacea. Lam. 26.— E. t. 181, / 1, 2, 3.—BI. t. 59, 

 f. 5. — Desh. E. 2, p. 295. Ovate-acute, thick, recurved, beaked and 

 bag-shaped, white, clouded with rose or purple. Upper valve flat, 

 somewhat lamellated, the lamellae depressed, the surface beneath them 

 pearly. Beak nearly flat, cartilage-canal scarcely concave. 4£. 

 S. America? "Resembles Cornucopia, but is not at all plicated."' 



O. Gibbosa. Lam. 27.— E. t. 182, /. 3, 4, 5. Ovate-oblong, 

 distorted, gibbous near the beaks, tinged with violet, lamellated : lower 

 valve bag-shaped : inner margin denticulated. 2f . Hab. ? 



O. Elliptica. Lam. 29.— Del. t. 17, /. 2.— Ch. 8, / 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. ? 2 



O. Angulata. W. S. t. 2, f. 8.— Conch. Mis. O. f. 10, 11.— 

 Gryph^ea Angulata, Lam. — Del. t. 20, f. 3. — Crouch, t. 12, f. 7. 

 Oval, arcuated at the base, tolerably strong, very inequivalve ; the 

 beaks greatly incurved and subspiral. Up£>er 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 ; low T er valve profound, usually affixed at 



1 According to the tablets at the French Museum, it forms but 

 one species with Tuberculata and Australis. 



O. Tuberculata. Lam. 24. — Ann. du Mus. 4, t. 67,/. 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. Australis. Lam. 28. Ovate, lamellar, not folded, dilated at 

 the ventral margin, retuse, violet, especially within ; lower valve bag- 

 shaped : inner edge denticulated. 2f . New Holland. 



2 0. Haliotoidea (Lam. SO), O. Deformis (Lam. 31) and O. 

 Fucorum (Lam. 32) must be expunged ; the characteristics of the 

 first being accidental, not essential, and the two last being merely 

 the fry of some larger species. 



