Calliostoma zizyphinum

(Linné, 1758)

Description (shell):
Shell regularly conical, straight-sided, up to 12-13 whorls; sculpture of regular spiral grooves and ridges traversed by fine prosocline growth lines. Last whorl with prominent peripheral keel bearing two broad ridges; ridges above suture in preceding whorls. Base of shell rather flat, inner lips reflected over shallow umbilical groove (C. zizyphinum-drawing).

Up to 30 x 30 mm.

Variable. Yellowish, pale pink, or violet with streaks and blotches of brown, red or purple. Blotches on keel generally darker, more frequent and more regular than on other parts of shell. Pure white or violet specimens occasionally found.

Head with papillate snout and finely papillate tentacles; mouth T-shaped when closed. Foot with anterior pedal gland, transversely ridged sole and papillate sides; four or five pairs of epipodial tentacles, lacking basal sense-organ. Operculum polygyrous (about 15 turns), shallowly concave.

Below LWNT on weed covered rocky shores, extending sublittorally on hard and soft bottoms to 300 m; tolerant of salinities down to 21 ä.

Distributed from Mediterranean, Canaries and Azores to Norway. All British and Irish shores, Helgoland (Distr. C. zizyphinum).