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Hypermastus coxi (Pilsbry, 1899)

Description: Shell relatively small. Protoconch very small. Early teleoconch whorls rapidly expanding, then spire strongly convex in profile, becoming straight in later whorls. Scars from outer lip positions faint, infrequent. Aperture short, about one-quarter of shell length; outer lip expanded, almost straight or weakly sinuous in profile. Shell glossy, colourless transparent.

Size: Up to 5.5 mm in length.

Distribution: Endemic to Australia. Known from Port Stephens southwards to Twofold Bay, NSW.

Habitat: Species of Hypermastus are parasitic on sand dollars (Warén, 1984), but there have been no observations specifically on the host of this species. Uncommon.

Comparison: The maximum size of mature shells is less than half that of H. mucronata.

Remarks: Laseron (1955) inadvertently interchanged the identification of H. muctronatus and H. coxi. His figures in Plate 1, figs. 9-11 labeled as H. mucronata are actually H. coxi.

Fig. 1: Middle Harbor, Sydney, NSW (C.032612)


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