304 TESTACEOUS MOLLUSCA. 



attenuated at the summit, which is produced in a long, narrow and 

 pointed beak, white, becoming clouded with violet towards the ventral 

 edge. Upper valve flat, not ribbed, lamellated by very close-set im- 

 bricated concentric flakes. Lower valve the larger, profound, thin, 

 its cavity slightly extending beneath the hinge-margin, with 6 or 7 

 narrow simple radiating ribs (the two central the coarser), which 

 render the margin (which is neither crenated nor toothed) jagged. 

 Inside pearly white ; scar longitudinally oval-oblong, superficial, not 

 coloured. Hob. ? 3f . . . 1^-. I have not been able to meet with this 

 species, whose described features approach very closely those found in 

 certain specimens of Parasitica. 



O. Senegalensis. Gmel. 3337, for Rojel, Adans. p. 202, t. 14, 

 / 5.— D. p. 279.— W. t. 11, /. 7%—Desh. ed. Lam. 7, p. 237. 

 Rounded, flattened, affixed by the entire surface, tolerably smooth, 

 of a deep reddish brown ; lower valve flat, upper slightly convex : 

 umbones minute, scarcely projecting: inside dirty white, hinge- 

 margin with granules on either side. 2. Senegal. 



O. Orientalis. D. p. 274 r for Ch.f. 660 {termed 0. Bilineata 

 by Bolten, and copied as 0. Radiata, E. t. 184, f. 4), from which 

 W. t.\l,f. 61. Parasitical, ovate or orbicular. Upper valve coarse, 

 convex, yellowish brown with black rays, or black and rayed with 

 yellowish brown : lower valve flat and white. 2. E. Indies. Is 

 apparently attached by the entire surface. 



O. Rosacea. — O. Parasitica, Ch. f. 997. — O. Plicatula, var. C. 

 ham. — 0. R., Desh. ed. Lam. 7, p. 236. Extremely variable in 

 shape, tolerably strong, rose-coloured, with one or two more or less 

 distinct smoke-coloured rays ; surface glabrous, devoid of distinct 

 lamellae, usually more or less tubercular. Valves of equal size ; the 

 upper one rather shallow, its entire periphery more or less dotted 

 inside with minute granules : the lower (if not attached by the entire 

 surface) plicated, and rather profound. Inside white, or greenish 

 white ; scar moderate, reniform ; cartilage-plate small. 2. China ? 

 Senegal ? Var. ? from L. Hood's Island. Both valves nearly flat, 

 pale olive, mottled here and there with pink or rose-colour ; surface 

 not tubercular, but very slightly scaly, there being somewhat in- 

 distinct concentric flattened lamellae. 



0. Chemnitzii. Hani. Z. P. 1845.— (Ch. f. 994.) Oboval, 

 generally sinistral, solid, greatly compressed : lower valve attached 

 by its entire surface : upper valve ranging in tint from dirty yellow 

 to dull reddish purple, having a peculiar gum-like glossiness, some- 

 what tuberculated, assuming a blistered appearance, not distinctly 

 lamellated. Beaks incurved. Margin of the upper valve obsoletely, 

 of the lower decidedly plicated. Inside tinged with green, the margin 

 roughened by small grains in one or the other valve : scar rather 



