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PYRAMIDELLIDAE


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Pseudoskenella depressa Ponder, 1973

Description: Shell very small, low spired, up to 2 teleoconch whorls. Protoconch (Type C) of 1 whorls, first whorl infolded. Teleoconch whorls strongly rounded, without sculpture. Aperture wide, almost circular, outer lip simple, inner lip slightly reflected outwards; columella without plait. Umbilicus narrowly open. Shell translucent becoming opaque white with age.

Size: Up to 1.5 mm in height.

Distribution: Endemic to Australia: southern Qld southwards and around southern Australia to south-western WA, including Tas.

Habitat: This species feeds on the tube worm Galeolaria caespitosa, the tubes of which form dense masses in the middle and lower intertidal levels in NSW. The molluscs position themselves around the opening of the tube or on the worm's operculum. When the worm extends it pinnules (fronds) to feed, the mollusc extends its proboscis and sucks fluid from the worm. (Ponder, 1973)

Comparison: No other NSW pyramidellid approached this in shell form. The most similar NSW species is Cornirostra pellucida (Laseron, 1954), in the Cornirostridae, which is larger with a wider umbilicus.

Fig. 1: Long Reef, Collaroy, Sydney (C.341792)

 

Copyright Des Beechey 2017