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MYTILIDAE |
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Musculus varicosus (Gould, 1861) Description: Shell equivalve, inequilateral, elongate, light in weight, inflated; umbo behind anterior end, incurved, projecting above dorsal margin. Valves twice as long as wide, wider posteriorly. Margin crenulated by external sculpture. Hinge without teeth. Ligament moderately long, almost straight. Interior smooth, muscle scars obscure, surface slightly nacreous. Exterior with 3 sculptural panels; anterior panel with about 10 widely spaced radial ribs, posterior panel finely, densely radially ribbed, central panel with only concentric growth ridges. Colour of exterior white with brown zones, sometimes having zigzag stripes. Interior slightly nacreous, white with brown patches or zigzag zones. Periostracum unknown. Size: Up to 16 m in length, usually less than 8 mm. Distribution: The Australian Museum collection holds specimens only from the Sydney region - from Pittwater southwards to Port Hacking. Habitat: Known only from beach washup. Comparison: This species is smaller than M. impactus, usually much smaller at around 8 mm in length. It is also more elongate. Fig. 1: Sydney, NSW (C.017538) |
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