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. Hab.? 32...13. 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 RosEL, Adans. p. 202, t. 14, 
SF. 5.—D. p. 279.—W. t. 11, f. 72.—Desh. ed. Lam. 7, p. 287. 
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. Orrentais. D. p. 274, for Ch. f. 660 (termed O. BiLttneata 
by Bolten, and copied as O. Haprara, E. t. 184, f. 4), from which 
W.t.11, 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. EH. Indies. Is 
apparently attached by the entire surface. 
O. Rosacra.—O. Parasitica, Ch. f. 997.—O. PricaruLa, var. C. 
LTam.—0O. 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 
lamelle, 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 bemg somewhat in- 
distinct concentric flattened lamelle. 
O. Cuemnitzir. Hanl. 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 guin-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 
