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RISSOELLIDAE


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Rissoella confusa robertsoni Ponder & Yoo, 1977

Description: Shell minute, globose, spire about equal to aperture height. Protoconch of 1 whorls, coiled about same axis as teleoconch. Teleoconch 2 whorls; whorls strongly convex, smooth apart from indistinct growth lines. Aperture not much expanded, outer lip thin and simple. Umbilicus variable from nearly closed to moderately wide. Shell initially colourless transparent, becoming opaque white with age.

Size: Up to 1.1 mm in length.

Distribution: This subspecies is restricted to a range from Central NSW southwards to northern Tasmania.

Habitat: "On algae in lower littoral and shallow sublittoral; uncommon" (Ponder & Yoo, 1977).

Comparison: See R. secunda.

Remarks: Rissoella confusa Ponder & Yoo, 1977 occurs as a three distinct geographic forms which were recognised as subspecies:

Rissoella confusa confusa Ponder & Yoo: 1977 tropical Indo-West Pacific as far south as central Qld.

Rissoella confusa robertsoni Ponder & Yoo, 1977: central NSW southwards to northern Tasmania.

Rissoella confusa umbilicata Ponder & Yoo, 1977: western SA and south-western WA.

Fig. 1: Green Cape, near Disaster Bay, NSW (C.101453 PARATYPE)

 

Copyright Des Beechey 2016