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Retusa iredaleana Hedley, 1915

Description: Shell elongate, involute, width slightly more than of shell length. Apex umbilicate (Fig. 2), protoconch visible at bottom of umbilicus. Last whorl with sides strongly constricted over middle part of shell. Aperture narrow over top half, wide and expanded outwards at bottom. Columella smooth, parietal wall with thin callus. Whole surface smooth or with coarse axial growth lines, with extremely fine spiral grooves on rare unabraded specimens. Shell translucent when fresh, becoming opaque white.

Size: Up to 4 mm in length.

Distribution: Identified specimens in the Australian Museum collection are from estuaries in the Sydney region, but the geographical range is probably much wider.

Habitat: Occurs in sediment associated with seagrass in the intertidal and shallow subtidal (Ponder, Clark & Dallwitz, 2000).

Comparison: Compared with Retusa atkinsoni, this shell is broader, always constricted around the middle and the outer lip is expanded anteriorly.

Figs. 1, 2: Middle Harbour, Sydney. (C.108921 SYNTYPE (1 of about 30)).


Copyright Des Beechey 2018