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RISSOIDAE


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Rissoina (Phosinella) allanae Laseron, 1950

Description: Shell glassy, translucent, with spire weakly convex. Protoconch of 1 whorls, with well-defined junction to teleoconch. Teleoconch of 6-7 whorls; early whorls moderately angled at top and bottom, latter whorls rounded. Sculpture clathrate; axial sculpture of narrow ribs, 16-23 on second-last whorl, crossed by finer spiral cords forming beads at intersections; 4-6 spirals on second-last whorl. Aperture lens or D-shaped, with broad anterior canal and narrow posterior canal; outer lip greatly thickened externally; inner lip callused, thickened at top and bottom. Colour translucent white, becoming opaque with age.

Size: Up to 6.9 mm in length.

Distribution: Endemic to Australia; Hervey Bay, Queensland, southwards to Woolgoolga, NSW; also Lord Howe Island and Norfolk Island.

Habitat: Collected alive from under stones intertidally. Most specimens available are empty shells from beach washup. Moderately common.

Comparison: The intersecting axial and spiral sculpture with beads at intersections distinguishes this species within the genus in NSW, although there are similar species in the tropics.

Synonymy: None

Fig. 1: Woody Head, Iluka, NSW (DLB5367)

 

Copyright Des Beechey 2010