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TRIGONIIDAE |
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Neotrigonia lamarckii (J.E. Gray, 1838) Description: Shell solid and heavy. Shape triangular-ovate, anterior and ventral margins uniformly rounded, posterior margin truncate, postero-dorsal margin straight or concave. Escutcheon defined. Exterior with 23-25 strong, radial ribs, bearing dense ovate nodules developing into scales posteriorly and towards ventral margin; grooves between radials deep, about same width as radials, with fine concentric threads. Interior nacreous silver or pink, grooved ventrally, with interlocking scalloped margin; muscle scars circular. Hinge very strong, with 2, narrow, elongate, deep sockets in left valve and two matching blade-like teeth in right valve. Shell colour light to dark brown with thin periostracum. Size: Up to 34 mm in length. Distribution: Endemic to Australia: off Tin Can Bay, Qld, southwards to Wollongong, NSW. Habitat: Subtidal, down to 150 m. Occasionally found as beach washup. Comparison: Compared to N. margaritacea, this species has more crowded nodules on the radial ribs (Fig. 2). The posterior slope is long and often concave, forming a well-defined and slightly depressed escutcheon. Fig. 1: Port Jackson, Sydney (C.010706) Fig. 2: Comparison of sculpture of N. margaritacea (left C.090775) with N. lamarckii (right C.010706) in oblique views.
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