Linné, 1758
Description (shell):
Shell solid, mature individuals especially robust and heavy; periostracum hispid in juveniles, missing from most of shell in adults. Spire of seven or eight tumid whorls, last whorl large (about 70 % of shell height); sutures deep. Sculpture of strong crescentic costae, spiral striae and prosocline growth lines. Costae do not extend to base of last whorl; 12-15 on penultimate whorl. Spiral striae numerous, major ridges separated by variable number of minor ridges to form a regular pattern; interaction with growth lines produces fine reticulation. A thick spiral keel, the siphonal fasciole, runs from base of shell to umbilical region. Aperture broadly oval, tapering adapically to a point; outer lip describes a high arc to tip of short, siphonal canal. Inner lip reflected over columella and large area of parietal region of last whorl (B. undatum-drawing 2); (B. undatum-with eggs).
Size:
Up to 110 x 68 mm.
Colour:
Buff, with darker bands above and below periphery; throat and peristome white (B. undatum-drawing).
Animal:
Cephalic tentacles long, distal portion slender, eyes at junction with broader basal portion. Siphon extends a long way from canal in active animals. Foot large, shield-shaped, with double-edged anterior margin; females with opening of ventral pedal gland on sole; operculum oval, with central nucleus (B. undatum-animal).
Habitat:
On hard and soft substrata, occasionally at LWST, but usually sublittoral down to 1200 m. Tolerates brackish water to 15ä.
Distribution:
Distributed from Iceland and northern Norway to the Bay of Biscay; common and often abundant (Distr. B. undatum).