(Linné, 1758)
Description (shell):
Shell is solid, oval-conic, with short, straight-sided or slightly coeloconoid spire. Whorls are slightly tumid, last whorl large (80 % or more of shell height); sutures are shallow. Sculpture of broad, low spiral striae and irregular growth lines. Last whorl with 11-14 spiral striae, becoming prominent basally as a keel over siphonal canal. Growth lines may produce irregular varices; in juveniles and in animals from sheltered habitats they may be raised to give frilled or imbricate surface to shell (var. imbricata ). Aperture is oval, with short siphonal canal, partially closed by columellar fold. Outer lip curves in more or less constant arc from origin to tip of siphonal canal, with little or no inflection at base. In juveniles it is thin and crenulate, later thickening and developing internal teeth. Inner lip is reflected over columella and last whorl as a broad glaze (N. lapillus-drawing).
Size:
Up to 42 x 22 mm.
Colour:
Commonly whitish, with brown or purplish throat but a range of monochrome and striped shell forms also occur.
Animal:
Distal two thirds of cephalic tentacles narrow, with eyes at junction with broader basal portion. Foot with double-edged anterior margin, posterior to which is the small pit of the accessory boring organ; in females the pit of the ventral pedal gland, used in depositing egg capsules, lies posterior to this; operculum is horn-coloured, oval, with a basal nucleus.
Habitat:
Abundant on all rocky shores, from MHWNT to MLWST, less common sublittorally to 40 m. Avoids low salinities and excessive weed cover, but tolerant of a wide range of exposure.
Distribution:
Widely distributed from Straits of Gibraltar to Arctic (Distr. N. lapillus).