Janthina prolonga Blainville, 1822
Description: Shell lightweight, globose, aperture more than half shell length. Spire whorls and last whorl rounded, aperture extended anteriorly in some shells. Whorls sculptured with weak, irregular V-shaped growth lines following the curves of the outer lip; spiral groove or ridge at periphery of last whorl absent or weak; a few weak spirals on base. Outer lip (when unbroken) with shallow sinus at periphery. Umbilicus closed by columellar callous. Colour purple, with diffuse, narrow pale violet band below suture.
Size: Up to 38.5 mm high, usually less than 30 mm.
Distribution: World-wide, in tropical and temperate seas; available Australian specimens range from southern Queensland southwards to Bermagui, NSW.
Habitat: Pelagic; found washed up on ocean beaches; uncommon in NSW.
Comparison: In this species the early spire whorls are lower than in J. exigua and J. umbilicata. The sculpture is weak, as in J. umbilicata, but irregular, giving a rough surface. The umbilicus is closed, in contrast to J. umbilicata. The outer lip sinus is shallow, in contrast to J. umbilicata and J. exigua where it is much deeper.
Synonym: The synonym Janthina globosa Swainson, 1826 was used by Iredale & McMichael (1962) for this species.
Remarks: Wilson (1993, pl. 44, figs. 38A, 38B) illustrated a specimen of this species, incorrectly identified as Janthina pallida (Thompson, 1840).
Figs. 1, 2: South coast of NSW (DLB4296)
Copyright Des Beechey 2008