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RISSOIDAE


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Rissoina (Rissoina) royana (Iredale, 1924)

Description: Shell large for genus, tall and slender, spire straight to weakly concave. Protoconch of about 2 whorls, with indistinct junction to teleoconch. Teleoconch up to 7 weakly convex whorls. Axial sculpture of broad, weak curved ribs, 30-40 on second-last whorl, fading out at periphery on last whorl. Spiral sculpture of microscopic threads, usually restricted to interspaces between axials. Aperture lens or D-shaped, with broad anterior canal and narrow posterior canal; outer lip expanded, with weak varix externally; inner lip callused, thickened at top and bottom. Colour white with large orange patches, sometimes with orange band below suture.

Size: Up to 16 mm in length.

Distribution: Endemic to Australia; Crowdy Head, NSW, southwards to Lakes Entrance, Victoria.

Habitat: On the continental shelf, 15-145 m. Uncommon.

Comparison: See R. ferruginea.

Synonymy: None

Fig. 1: HOLOTYPE Off Twofold Bay, NSW, in 18-46 m (C.102384)

 

Copyright Des Beechey 2010