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Pinctada maculata (A. Gould, 1850)

Description: Description based on that of Hynd (1954) for the species throughout the Indo-West Pacific. Shape Oblique when juvenile, almost circular as adult. Shell with left valve more inflated than right; umbo near anterior end of dorsal margin; dorsal margin straight, anterior margin with deep byssal notch in right valve, posterior margin straight or weakly concave, ventral margin rounded. Hinge line straight, ligament in a broad triangular pit behind umbo. Interior nacreous, with a wide non-nacreous margin which is variegated blue-black and white; single large muscle scar present. Exterior smooth initially, developing concentric overlapping laminae marginally; finger-like concave growth processes. Shell with wide variety of patterns and colours, often with white patches, rays or flecks; finger-like processes never banded.

Size: Up to 55 mm in length.

Distribution: Indo-West Pacific; In Australia from Dampier Archipelago, North West Australia, around northern Australia, to Clarence River, NSW.

Habitat: Lives attached to solid substrates in the shallow subtidal.

Comparison: This species has a maximum length of 55 mm, so is smaller than P. fucata and P. albina. It is more inflated than those two species, but is so variable that it is difficult to identify with certainty. Because of the difficulty of identifying a NSW specimen, the one illustrated is that shown by Hynd (1954, Pl. 6, Fig.2), even though it is from the other side of the Pacific Ocean.

Hynd (1954) pointed out that the foliaceous processes are banded brown and white in P. fucata, but unbanded in this species. This is useful for separating the species if the shells are in good condition, but in most specimens the foliaceous processes are not developed or are eroded, so the character is not always useful for identification.

Fjg. 1: Tuamotu Archipelago. Gambier Islands, Mangareva Atoll (C.017196).


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