308 TESTACEOUS MOLLUSCA. 



more or less obtuse rib-like longitudinal folds, which are generally 

 imbricated by foliaceous concentric lamella? (varying in closeness and 

 elevation), and are rarely profound : inside centrally whitish, margin 

 quite entire, often with a few minute denticles at the hinge : beaks 

 not prominent. China ? 



O. Glaucina. Lam. 42. Oval or oval-oblong, tumid, with the back 

 varying from purplish brown to tawny -purple, having a peculiar 

 resinous lustre, with obtuse and transversely wrinkled folds : posterior 

 side denticulated near the hinge. — Var. Disk irregular, almost de- 

 void of folds. 2^-. Hob. ? Certain large and strong specimens of 

 Plicata sufficiently agree ivith this description. 



O. Sinensis. Gmel. 3335, and D. p. 275, /row Ch.f. 668 (termed 

 by Bolten 0. Pile-Adamitica), copied E. t. 184, /. 1, and W. 1. 11, 

 f. U.—Hanl. Conch. Mis. Os/f. 9, 12. — 0. Fusca, Lam. 43. Strong, 

 more or less orbicular, of an uniform dull purple, with blunt radiating 

 folds and concentric lamella? ; subequivalve, usually affixed by about 

 half its lower surface, devoid of tubular processes of attachment. 

 Inside whitish, except at the margin, which partakes of the external 

 colouring, and is not at all scabrous, but displays some coarse raised 

 wrinkles at the extremities of the large and broad cartilage-area; 

 scars in general brownish, oboval or suborbicular. Var. A (type). 

 Folds few, scarcely imbricated. Var. B. Folds more numerous, im- 

 bricated or even squamular where crossed by the rather distant 

 lamella?. Var. C. Roseate-brown : folds numerous, subangulated, 

 closely imbricated, obsolete above. 5 or 6. China? Var. C.from 

 L. Hood's Island. 



O. Turbinata. Lam. 44. — (? Ch. f. 668.) Oval, dark brown, 

 depressed near the ventral edge, obliquely turbinated near the beaks, 

 strongly plaited by large transversely wrinkled folds : inner edge 

 blue, not scabrous. 3f. Indian Ocean. " Allied to 0. Crista- 

 galli " (Lam.), of which it may possibly prove a variety. 



O. Crista-galli.— (Arg. t. 20,/. D.— Kn. 5. t. 16,/. 1.)— Mytilus 

 C, Lin. U65.—D.p. 299.— W. t. 12,/. 1.— 0. C, Ch.f. 683, 4.— 

 Lam. 45. — E. t. 186, /. 3, 4, 5. — Sow. G. — Reeve, Syst. t. 121, /. 2. 

 Obovate, tolerably strong, granular, not flaky, unarmed, of an uniform 

 tint, ranging from ferruginous to livid purple, with large angular 

 radiating folds, that vary in number, and extend almost to the 

 incurved beaks : valves almost alike, the lower with a tendency to 

 form elongated processes of attachment : inner margin scabrous in 

 one or both valves. 3. Indian Ocean; frequently in grou ± s, but not 

 attached by the entire surface. 



0. HYOT:is.—(Gualt. t. 103, / A.)— Mytilus H., Lin. Sys. 1155 ; 

 Mus. Ulr 538.— D. p. 300.— W. t. 12, /. 2.— 0. H., Ch. f. 685.— 

 Lam. 47. — E. t. 186,/. 1. — Desh. E. 2, p. 298. Suborbicular, more 



