Sinum zonale (Quoy & Gaimard, 1833)
Description: Shell flattened, with very low spire and wide aperture. Sculpture of fine growth lines parallel to outer lip, and in some specimens, weak spiral ribs and grooves (only visible with magnification). Columella smooth; outer lip sinuous, thin and sharp. Exterior matt white, interior polished white; apex sometimes purple. Covered with thin brown periostracum when alive.
Size: Up to 34 mm wide.
Distribution: Endemic to Australia; Sydney, NSW, to Geraldton, WA.
Habitat: Lives intertidally and subtidally on sand and mud flats. Rare in NSW.
Synonym: Ectosinum pauloconvexum Iredale, 1931 is based on a specimen, probably subfossil, dredged from Sydney Harbour.
Remarks: This species has previously been reported as having a range throughout southern Australia, extending up the east coast to Queensland. It is now considered that two species occur in this range; S. zonale with a southern distribution and northern limit of Sydney, and S. incisum with an Indo-West Pacific distribution and southern limit around Sydney. The shells are very similar, but S. incisum has spiral ribs and grooves on the dorsal surface
Figs. 1,2: Locality unknown (C.unreg)
Copyright Des Beechey 2000