Lacuna vincta

(Montagu, 1803)

Description (shell):
Shell thin, with five to six tumid whorls; periostracum thin, though thickened patches may line sutures. Shell smooth to the naked eye, but with fine spiral ridges and prosocline growth lines. Umbilicus conical, with a prominent groove or chink bounded on apertural margin by inner lip, and on abapertural side by upturned outer lip; umbilical groove smooth, aperture below drawn out and slightly angular (L. vincta-drawing).

Up to 10 x 5 mm.

Pale horn colour with two to four red-brown bands on last whorl; upper whorls with two colour bands, becoming faint towards apex which is generally purplish. Banding occasionally faint or absent.

Snout long, broad, with slender cephalic tentacles arising from base. Foot elongate, with double edged anterior margin; two short, flat metapodial tentacles project from below operculum (L. vincta-animal).

Common on seaweeds, occasionally on Zostera , at LWST, sublittorally to 40 m. Tolerant of salinities down to 20 รค.

A circumboreal species extending south in Europe as far as the Channel and, less frequently, the Atlantic coasts of France. On suitable weed-covered shores on all British and Irish coasts and off Helgoland (Distr. L. vincta).