Colpospira atkinsoni (Tate & May, 1900)
Description: Protoconch 1½ whorls, teleoconch 14 whorls in adult shells. Whorls overall convex in outline, suture weakly incised. Whorls spirally ribbed; latter whorls with a strong, sharp spiral keel at centre of each whorl, with one or more weaker ribs above and below. Axial sculpture of growth lines conforming to shape of outer lip sinus. Inner lip of aperture reflected outwards at base; outer lip thin, with a deep sinus, lip usually broken. Base with up to 10 weak and irregular riblets. Colour uniformly white or fawn. Operculum circular, corneous.
Size: Up to 22 mm in length.
Distribution: Endemic to Australia; Crowdy Head, NSW, southwards to Eyre Peninsula, SA, including Tasmania.
Habitat: Recorded from 37-750 m. Moderately common.
Comparison: This unicoloured shell with a strong central keel on convex whorls is similar to C. smithiana, but the latter is smaller, always white, and has four strong keels.
Synonymy: Originally described at Turritella tasmanica Tenison-Woods, 1876, but that name was preoccupied. T. godeffroyana (Donald, 1900) is a synonym.
Remarks: The strong spiral keel at the periphery is a constant feature, but the number and strength of additional spirals is variable. Some specimens show three spiral keels, with the one on the periphery only slightly stronger than the other two.
Fig. 1: East of Babel Island, Bass Strait, in 119 m (C.077378).
Copyright Des Beechey 2006