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Pinctada chemnitzii (Philippi, 1849)

Description: Shape Shell with left valve more inflated than right; umbo at anterior quarter of dorsal margin; dorsal margin straight, anterior and posterior auricles well developed; anterior margin with deep byssal notch in right valve, posterior margin concave below well-developed posterior auricle, ventral margin rounded. Hinge line straight, ligament in a broad triangular pit behind umbo. Interior nacreous with a wide non-nacreous margin; nacreous area of left valve significantly greater than right (Fig. 2); single large muscle scar; nacreous area weakly corrugated. Exterior fairly smooth, irregularly foliaceous. Shell colour mid brown, often rayed with purple or white.

Size: Up to 85 mm in length.

Distribution: Indo-West Pacific; in Australia, from Gove, Northen Territory, through Queensland to northern NSW, and rarely to Sydney.

Habitat: Lower intertidal and shallow subtidal, attached by byssus to solid substrates.

Comparison: In this species the posterior auricle is large, causing the posterior shell margin to be strongly concave. The nacreous layer internally is significantly larger in the left valve than in the right. This character is also observed in other species, but it is more noticeable in this species. Also see P. fucata.

Fig. 1: Townsville, Queensland (C.119130)

Fig. 2: Same specimen as Fig. 1

 

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