(da Costa, 1778)
Shell solid, conical, with five to six tumid, rapidly expanding whorls. Sculpture of prosocline lines and occasional clear growth disturbances which may reflect annual increments; young specimens with thin spiral ridges and grooves on first three whorls, in older shells often abraded to reveal underlying nacre, subsequent whorls being smooth. Columella thick, with prominent tooth near base; inner lip reflected over umbilicus which remains as slight depression or chink in adults shells, umbilicus of juveniles may be open (O. lineatus-drawing).
Up to 30 x 25 mm.
Cream or horn-coloured, heavily overlain with reddish-brown, purple, or green zigzag streaks; base of shell less heavily pigmented. Iridescent nacre on inner surface.
Cephalic tentacles with lobed sides; foot with finely papillate margin and tuberculate sides; three pairs of epipodial tentacles, each with two sensory papillae at base. Operculum flat, polygyrous (around 15 turns).
On rocky or boulder shores from MHWS-MLWN, avoiding excessive exposure and deposits of shingle or sand.
A southern species with a rather patchy distribution in the British Isles, occurring in the western basin of the English Channel, the Welsh coast north to Anglesey, and the south and west coasts of Ireland. Transplant experiments to the southern North Sea (Distr. O. lineatus).