(Gmelin, 1791)
Description (shell):
Shell depressed, conical, with five to six tumid whorls dipping sharply and abapically into sutures. Sculpture variable; usually spiral ridges and distinct growth lines; occasional shells smooth or with only one or two furrows at periphery and fine sculpturing near umbilicus. Latter form common in Greenland, spiral ridging common in European and American waters. Umbilicus wide, partly occluded by inner lip.
Size:
Up to 7 x 8 mm.
Colour:
Cream, pale tan, or pale orange, with blue-green refringence internally.
Animal:
Foot with broad, double-edged anterior and smooth sides; seven pairs of epipodial tentacles each with sense-organ below base. Operculum polygyrous (10-12 turns), markedly concave.
Habitat:
Under stones, on weeds and on Laminaria holdfasts from ELWST to 75 m.
Distribution:
A northern species extending south from Arctic waters to north-west coasts of British Isles and west coast of Norway (Distr. M. groenlandicus).