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CARDIIDAE |
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Acrosterigma cygnorum (Deshayes, 1855) Description: Shell moderately light in weight. Shape semicircular, length less than height, weakly angled posteriorly, umbo on midline. Lunule wide, poorly defined, escutcheon absent. Exterior with 35-44 scaled radial ribs continuous from umbo, intervening interspaces much narrower. Interior with exterior ribs showing through; anterior and posterior muscle scars unequal, pallial line not detectable; margin crenulate by external ribs. Interior white, sometimes pink. Hinge as for family. Ligament external, short. Shell colour white, blotched or spotted with reddish-brown, yellow at margin when fresh. Size: Up to 47 mm in length. Distribution: Off Port Hacking, Sydney, southwards and around southern Australia, to Fremantle, WA, including Tas. Habitat: Known from beach washup and dredged down to 80 m. Uncommon in NSW, common in southern Australia. Comparison: This is a fairly lightweight shell similar to Fulvia tenuicostata, but the radial ribs cover the whole surface from umbo to ventral margin, and the umbon is never purple. Synonymy: There are two previously recognised synonyms – Laevicardium gaillardi Fischer-Piette, 1977 and Acrosterigm abrolhosensis J. Vidal, 1999. Fig. 1: Off Eden, NSW in 73-91 m (C.145095) |
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