(Linné, 1758)
Description (shell):
Shell solid, conical, with stepped profile and marked peripheral keel on last whorl; on upper whorls keel lies immediately above deep suture line. Up to eight whorls. Sculpture of short, nodular costae on apical part of each whorl, below which are a variable number of spiral ridges and grooves. In intertidal specimens ridges are often smooth, in specimens from deeper water they may be markedly imbricate. Umbilicus large and deep, partly occluded by inner lip, edged by thickened spiral ridge (G. magus-drawing).
Size:
Up to 30 x 35 mm.
Colour:
White, grey, or yellowish in colour with irregular brown, red, or purple streaks and blotches.
Animal:
Snout densely papillated, cephalic tentacles setose; foot with papillate margin and three pairs of epipodial tentacles. Operculum polygyrous (13-15 turns), slightly concave.
Habitat:
On weed, under stones, and on shingle beaches at ELWST. Sublittoral, on muddy gravel, to 70 m.
Distribution:
Distributed from Mediterranean and Azores to western basin of English Channel, west coast of Britain, and north to Shetland (Distr. G. magus).