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Show 916 MR. G. F. ANGAS ON AUSTRALIAN MOLLUSCA. [Nov. 28, liar to Australia. The valves are connected internally by an ossicle in the cartilage, are rough outside, and somewhat pearly within. The left valve is nearly flat and triangular; whilst the right one is convex, and attached by its front slope to the upper surface of flat sandstone rocks which are laid bare at low water. It occurs near Port-Jackson Heads. I have also procured fine large specimens from Port Lincoln, in South Australia. Length 2\ inches. Order VENERACEA. Fam. MACTRID^E. 27. TRIGONELLA CONTRARIA. Mactra contraria, Desh. P. Z. S. 1854; Reeve, Conch. Icon. Mactra, pl. 17. f. 86. Somewhat like M. rufescens, Lam., but flatter and more beaked at the sides, with the umbones smooth, and stained with two violet rays. Rare in Port Jackson. Length If inch. 28. TRIGONELLA LUZONICA. Mactra luzonica, Desh. P. Z. S. 1854; Reeve, Conch. Icon. Mactra, pl. 16. f. 81. A neat species, more or less rayed with brown, and tinged with purple at the umbones. Dredged in Middle Harbour on a sandy bottom, also in Botany Bay. Length 1 inch 3 lines. 29. TRIGONELLA PUSILLA. Mactra pusilla, A. Adams, P. Z. S. 1855, p. 226. A pretty, little, shining species, either white or rayed with brown. Dredged in Middle Harbour along with the foregoing. Length 7 lines. 30. *SPISULA CRETACEA. Spisula cretacea, Angas, antea, p. 909, Pl. XLIV. f. 6. A dull-white, chalky-looking shell, not unlike in form to the British S. subtruncata. Dredged in Port Stephen. Length 10 lines. 31. SPISULA CORBULOIDES. Mactra corbuloides, Desh. P. Z. S. 1854 ; Reeve, pl. 19. f. 103. 1 Mactra rostrata, Spengler, Skrift. Nat. Selsk. v. p. 115. A stout, gibbous, trigonal species, strongly keeled from the umbones, and covered with a pale greenish-olive epidermis. Dredged in Illawarra Lake. Length 11 lines. A dwarf variety is found in Rushcutter's Bay, Port Jackson, and also at Moreton Bay; it measures 5 lines in length. 32. *SPISULA PRODUCTA. Spisula producta, Angas, antea, p. 909, Pl. XLIV. f. 7. A small, whitish, triangular, somewhat compressed species, pro- |