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TRIGONIIDAE |
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Neotrigonia margaritacea (Lamarck, 1804) Description: Shell solid and heavy. Shape approximately ovate, anterior and ventral margins uniformly rounded, posterior margin truncate, postero-dorsal margin straight. Exterior with about 22 strong radial ribs bearing nodules: these domed anteriorly, conical erect or sloping medially, and finer erect posteriorly. Concentric riblets present between radial ribs. Interior nacreous, purple or pink, fading with age, grooved ventrally, with interlocking scalloped margin; muscle scars close to hinge. Hinge very strong, with 2, narrow, elongate, deep sockets in left valve and 2 matching blade-like teeth in right valve. Shell colour fawn with dark brown periostracum. Size: Up to 50 mm in height. Distribution: Endemic to Australia. Off Forster, NSW, southwards and around southern Australia, to Esperance, WA, including Tas. Habitat: Shallow subtidal on sand and sandy mud down to 140 m; occasionally washed up alive on beaches in Vic and Tas. Occurs uncommonly in Twofold Bay, southern NSW, but it becomes increasing rare further northwards. Synonymy: Trigonia antarctica Péron & Lesueur, 1807, T. pectinata Lamarck, 1819 and T. nobilis A. Adams, 1854 are previously recognised synonyms. Neotrigonia bednalli (Verco, 1907) (NEW SYNONYM) was based on specimens from SA, which vary a little in shape from typical N. margaritacea. This name was originally published as Trigonia margaritacea var. bednalli Verco, 1907 , but it has been elevated to species rank by some authors (e.g. Atlas of Living Australia). This synonym was recognised by Glavinic (2010, p. 36), but not published. Treating Trigonia margaritacea var. bednalli as a synonym of N. margaritacea implies that Neotrigonia horia Cotton, 1953, previously considered as a synonym of N. bednalli, is also a synonym of N. margaritacea (NEW SYNONYM). Fig. 1: Twofold Bay, NSW, in 18-27 m (C.090775)
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