Epitonium tacitum (Iredlae, 1936)
Description: Shell slender for genus, whorls disconnected, joined only by axial ribs. Whorls rounded, with 7-9 axial ribs per whorl. Ribs aligned from whorl to whorl, thick, rolled back, about as wide as high, not peaked, terminating in coarse rib beside lower half of aperture. Interspaces with spiral threads, crossed by microscopic axial grooves (Fig. 2). Aperture oval; outer lip with normal rib. Umbilicus closed or slightly open. Colour white. Operculum corneous.
Size: Up to 22 mm in length.
Distribution: Endemic to Australia. Darwin, NT, around northern Australia to Bermagui, NSW. Also reported from Western Port, Victoria (Macpherson & Gabriel, 1962).
Habitat: Most specimens are empty shells from beach washup, with a few down to 10 m. In NSW at least, it is restricted to the outer part of estuaries, with most specimens coming from Sydney Harbour and Port Stephens.
Comparison: See "Identification of the NSW species of Epitonium" in the introduction to this family.
Remarks: Wilson (1993, p. 279) was in error in giving a southern Australian range for this species.
Fig. 1: Port Stephens, NSW (C.345617)
Fig. 2: Same specimen as Fig. 1 showing detail of sculpture
Copyright Des Beechey 2008