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Show 934 MR. G. F. ANGAS ON AUSTRALIAN MOLLUSCA. [Nov. 28, Jackson Heads. Length 2 inches 4 lines. The interior of the lower valve is of a peculiar horny green colour. Fam. OSTREID^E. 133. OSTREA PURPUREA. Ostrea edulis, var. purpurea, Hanley, Conch. Miscel. pt, 3. This is the common " Mud-oyster," which supplies the Sydney markets. Mr. Hanley regards it as a variety of Ostrea edulis, Linn., a species that varies extremely according to its station in salt or brackish waters. On careful comparison of the Port Jackson shells (especially the young) with those of Europe, I am of opinion that the former may be separated as a distinct species under the name purpurea. The laminate scales are much larger, more regularly frilled, and the valves are dentate at the margins; the purple colouring prevails more or less throughout, and in the young shells exhibits a radiate style of painting. It occurs in various parts of Port Jackson and the other harbours of New South Wales. My largest specimen is from Johnson's Bay, and measures 6 inches across. 134. OSTREA MORDAX. Ostrea mordax, Gould, Proc. Boston Nat. Hist. Soc. iii. p. 346 ; United States Exploring Expedition (Mollusca), pl. 43. f. 575 a, b. The "Rock-oyster" of the colonists. "The horizontal digitations of the upper valve fitting into the erect canine teeth of the lower valve, together with the denticles within, and the black elevated cicatrice, may serve to identify this species."-Gould. The interior is white, stained with blackish purple towards the margins. It is excellent eating and of a delicious flavour. Common everywhere, attached to rocks between tide-marks. Length 2 inches ; breadth I inch 7 lines. 135. OSTREA CIRCUMSUTA. Ostrea circumsuta, Gould, Proc. Bost. Nat. Hist. Soc. iii. p. 346 ; United States Exploring Expedition, pl. 43. f. 576 a, b. This is a species of rare occurrence; it is of a narrow elongated form, denticulated and tinged with violet around the margin. The interior is pearly white, with the scar of the adductor muscle violet. Botany Bay. Length 2 inches ; breadth 1 inch. 136. *OsTREA VIRESCENS. Ostrea virescens, Angas, antea, p. 911, Pl. XLIV. f. 13. A handsome species, very orbicular, frilled round the margins, with the cardinal area large, flat, and triangular, and the interior of a peculiar green hue. Attached to rocks and madrepores at low tides in Watson's Bay. Length H inch. |