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RISSOIDAE


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Onoba (Ovirissoa) rubicunda (Tate & May, 1900)

Description: Shell variable in shape from tall with almost straight spire outline to pupoid with strongly convex spire outline. Protoconch of 1 smooth whorls, with well defined junction to teleoconch. Teleoconch up to 3 moderately to strongly rounded whorls. Shell smooth and glossy without spiral or axial sculpture. Aperture ovate, weakly channelled posteriorly, outer lip thickened by varix externally. Umbilicus closed. Colour translucent colourless to dark reddish brown, becoming opaque with age.

Size: Up to 2.5 mm in length.

Distribution: Endemic to Australia: Off Mackay, Queensland, southwards and around southern Australia, to off Cape Adieu, South Australia.

Habitat: Known from beach washup and down to 200 m. Common.

Synonymy: A rare colour form with two brown bands was described as Rissoa pulvillus Hedley, 1906 (Fig. 3). Elongate specimens were named as Estea figula Laseron, 1950.

Remarks: Despite the species name, most specimens are colourless or white, only a few being reddish brown.

Fig. 1:  Manly Beach, Sydney, NSW (C.355305)

Fig. 2: Batemans Bay, NSW (C.355332)

Fig. 3: Original figure of Rissoa pulvillus from Hedley (1906)

 

Copyright Des Beechey 2010