Epitonium minorum (Iredale, 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 or thin, erect or rolled back, not peaked, lamellate at upper suture, sometimes terminating on base in thick cord beside inner lip of aperture. Interspaces smooth or with faint spiral threads, crossed by axial growth lines (Fig. 2). Aperture oval; outer lip with normal rib externally. Umbilicus closed or slightly open. Colour white. Operculum corneous.
Size: Holotype 24 mm in length.
Distribution: Holotype is from Sydney Harbour.
Habitat: Known from empty beach shells.
Comparison: See "Identification of the NSW species of Epitonium" in the introduction to this family.
Remarks: It is difficult to diagnose this species confidently. Iredale described it as having "the whorls closely adjoined and is pure white", and "few varices which are rather flattened", but specimen lots from Sydney Harbour show whorls separated and joined only by axial ribs, the colour either white or fawn, and axial ribs varying from thin and erect to rolled back. Whether it is different to the topical species Epitonium philippinarum (Sowerby, 1844) (Fig. 3b), which is found in Queensland, remains to be determined. Its relation to the southern species Epitonium godfreyi (Cotton, 1938) (Fig. 3a), which has more developed axial ribs, also needs to be determined. Some authors (eg, Macpherson & Gabriel, 1962) appear to have combined the eastern and southern shells as a species, while others (eg Wilson, 1993) combined the Queensland and NSW shells.
Fig. 1: HOLOTYPE of Epitonium minorum. Sydney Harbour (C.060644)
Fig. 2: HOLOTYPE showing details of sculpture.
Fig. 3: (a) Epitonium godfreyi C.unreg South Australia (b) Epitonium philippinarum C.169501 Port Douglas area, Queensland
Copyright Des Beechey 2008