Turbo (Subninella) undulatus Solander, 1786
Description: Shell solid, wider than high, with spirally ribbed, rounded whorls covered with a thin, brown periostracum. Aperture circular, outer lip thin, simple. Umbilicus widely open, columella smooth. Operculum calcareous, circular, internally flat and brown, externally white with marginal flange and central dome. Exterior colouration of zigzag axial streaks of white and dark green; interior nacreous; umbilical area and columella white.
Size: Up to 61 mm wide, 57 mm high.
Distribution: Endemic to Australia: Coolangatta, Queensland, to Bremer Bay (east of Albany), WA, including Tasmania.
Habitat: On exposed and semi-sheltered rocky shores, among algae and in crevices, at mid-tide level and below. Common.
Synonymy: The spiral ribbing of this species is variable in strength. Some West Australian and Tasmanian shells are almost completely smooth, but NSW shells are usually ribbed, the ribbing being stronger on specimens from northern NSW. The strongly ribbed eastern Australian form has been referred to as Subninella anguis (Gmelin, 1791), but as there is a continuous gradation from smooth to heavy ribbing it does not justify separation.
Remarks: Living specimens usually have the colour obscured by the brown periostracum, but it is thin and flaky and rapidly wears off dead shells.
Fig. 1: Kurnell, Botany Bay, NSW (C.150040)
Fig. 2: Boat Harbour, Cronulla, NSW (C.445898)
Copyright Des Beechey 2004