Sigapatella hedleyi Smith, 1915
Description: Shell low, coiled, spire whorls rounded, last whorl concave. Apex small and prominent, nearly central; last whorl greatly expanded to form almost circular base. Sculpture of oblique growth lines, almost concentric towards the last whorl margin. Basal margin sharply angled; base very concave, last whorl overhanging base; aperture occupying about half base area. Exterior white or fawn, sometimes with brown apex; interior white. Periostracum very thin or absent.
Size: Up to 15 mm diameter, 4 mm high.
Distribution: Endemic to Australia; Moreton Bay, Queensland, around southern Australia to south-western WA, including Tasmania.
Habitat: Lives subtidally, down to 80 meters; empty shells occasionally found in beach washup. The few live taken examples seen have been attached to the inner surface of dead bivalves. Uncommon.
Comparison: This species has the last whorl concave above the periphery, and the base is very concave. In S. calyptraeformis all the whorls are rounded and the base is not so strongly concave.
Synonymy: This was misidentified in early Australian literature as Sigapatella tenuis Gray, 1867 (a New Zealand species), Calyptraea pellucida Reeve, 1859 (a tropical Indo-West Pacific species) and Calpytraea scutum Lesson, 1830 (New Zealand).
Fig. 1: Middle Harbour, NSW (C.032654)
Fig. 2: Same specimen as Fig. 1
Fig. 3: Same specimen as Fig. 1
Copyright Des Beechey 2007