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Show 908 MR. G. F. ANGAS ON NEW AUSTRALIAN MOLLUSCA. [Nov. 28, 5. On a New Genus and some New Species of Marine Mollusca from Port Jackson, New South Wales. By GEORGE F R E N C H ANGAS, F.L.S., C.M.Z.S. &c. (Plate XLIV.) Genus ALICIA, Angas. Shell inequivalve, transversely ovate, thin, slightly compressed, not gaping; beaks entire, interior subnacreous. Hinge composed of a .posterior more or less prominent callus in the right valve, fitting into a corresponding depression in the left valve, and an anterior elongated marginal lamellar tooth or ridge; cartilage internal, situated perpendicularly under the umbones, and covered by a large triangular ossicle. Muscular impressions moderate; pallial line sinuated. This genus has much the appearance externally of Periploma, but the ossicle is large and triangular as in Lyonsia. It differs from both genera in the cartilage not being supported by projecting spoon-shaped processes, and in its being perpendicular to the umbones. ALICIA ANGUSTATA, n. s. (Pl. XLIV. fig. 1.) Shell elongately oblong, white, surface of valves (under the lens) very finely decussated, inequilateral; anterior side five-sixths the length of the shell, rounded at the extremity, the dorsal margin slightly convex; posterior side truncate at the extremity, the dorsal margin incurved, umbonal slope angulated; ventral margin almost straight. The hinge with the posterior callus in the right valve prominent and tooth-like, and the corresponding depression in the left valve bordered by a slightly raised ridge. Pallial sinus deep, extending to half the length of the shell. Long. 6|, alt. 3, lat. 1| lines. Hab. Port Jackson. Dredged inside South Head Reef. ALICIA ELEGANTULA, n. s. (Pl. XLIV. fig. 2.) Shell oblong, white, obsoletely concentrically plicate, very minutely decussated, inequilateral; anterior side three-fifths the length of the shell, rounded; posterior side roundly truncate, the dorsal margin concave, umbonal slope angulated ; ventral margin convex. The hinge with the posterior callus almost obsolete. Pallial sinus deep, extending to the umbones. Long. 5h, alt. 3, lat. 1^ lines. LLab. Port Jackson. Dredged between Watson's Bay and " Sow and Pigs " reef. THRACIA MODESTA, n. s. (Pl. XLIV. fig. 3.) Shell ovate, thin, white, rather ventricose, surface of valves irregularly concentrically striate, inequilateral, beaks posterior ; anterior side rotundate; posterior side obliquely truncate, the dorsal margin |