Vanikoro expansa Sowerby. 1901
Description: Shell moderately light in weight, spire flat or slightly elevated. Protoconch smooth, elevated. Teleoconch initially with elevated, inclined lamellae, extending over 1 ½ whorls, about 18 in total. Lamellae followed by sudden transition to fenestrate sculpture of axial ribs and spiral cords about equal in strength, forming square pits between. Fenestrate sculpture progressively weakens to irregularly spaced axial folds crossed by spiral threads, with beaded intersections, and then spirals threads alone. Aperture wide; outer lip semicircular, smooth; inner lip of aperture smooth. Umbilicus almost closed. Colour white.
Size: Up to 17 mm high.
Distribution: Indo-West Pacific; in Australia, north-western WA, around northern Australia to Shellharbour, NSW.
Habitat: Probably shallow subtidal. All specimens seen are dead beach collected. Moderately common.
Comparison: See V. cancellata.
Synonymy: This species may be the same as Vanikoro fenestrata (A. Adams, 1863), reported from Japan by Okutani (2000).
Remarks: In common with other vanikorids, the shell sculpture changes dramatically as the species grows. Shells of 5 mm in height have the strong fenestrate sculpture on the last half whorl. Shells of 9 mm usually have axial ribs crossed by spiral cords, beaded at the intersections, on the last half whorl. Shells of 12 mm usually show only spiral threads, often formed as primaries with a few weaker secondaries between, on the last half whorl.
Fig. 1: 3977-1 Shelly Beach, south of Yamba, NSW (C.358901)
Fig. 2: 3978-1 Same specimen as Fig. 1
Fig. 3: 3996-1 Broome, north-western Australia (C.051054). (Photo Sue Lindsay, Australian Museum)
Copyright Des Beechey 2007