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Merelina gracilis (Angas, 1877)

Description: Shell moderately elongate, spire weakly convex. Protoconch of 1 whorls bearing strong nodulose spiral threads with distinct junction with teleoconch. Teleoconch up to 4 rounded whorls. Whorls sculptured with spiral cords, 2 on first whorl increasing to 4 or 5 on second last whorl, with axial ribs weaker or about same strength, forming strong beads at intersections; last whorl with further 3 unbeaded spirals on base. Aperture ovate, with neither anterior or posterior canal; outer lip with very strong varix externally. Umbilicus closed. Colour uniformly fawn to mid-brown, occasionally with white spiral band.

Size: Up to 3.1 mm in length.

Distribution: Endemic to NSW: Woody Head, Iluka, southwards to Malacoota, Victoria.

Habitat: Lives intertidally in rock pools, usually with clean sand, where it probably grazes on diatoms on rock surfaces (pers. comm. Francesco Criscione). It probably also lives subtidally, but the depth range is unknown. Empty shells are common in beach washup.

Synonymy: Rissoa devecta Tate, 1899 has previously been recognised is an unnecessary replacement name.

Remarks: The spiral threads on the protoconch are not obvious in most mature shells of this species, apparently being easily worn away. References to this species in Tasmania, South Australia and West Australia are probably misidentifications of Merelina cheilostoma (Tennison-Woods, 1877).

Fig. 1: Little Coogee Bay, Sydney, NSW (C.348539)

Fig. 2: Fairlight, North Harbour, Sydney, NSW (C.348492)

 

Copyright Des Beechey 2010