Shell tall, narrow, conical, up to 14 flat-sided whorls; sutures deep. Sculpture of spiral striae and transverse costae, interacting to give three rows of close set, rounded tubercles (more elongate near aperture); base of last whorl devoid of tubercles but with two spiral ridges. Aperture small, narrow, oval with short siphonal canal; canal wall with conical notch on abapertural side. Outer lip crenulate, inner lip reflected over columella; no umbilicus (C. tubercularis-drawing).
Up to 6.5 x 2.3 mm.
Chestnut-brown, tubercles and columella pale.
Head without a snout; cephalic tentacles long, slender, setose at tip. Mantle edge simple, drawn out into short siphon on the left. Foot with a propodial flap behind anterior margin; prominent posterior pedal gland on sole. Operculum thin, spiral, with few turns; opercular lobes large.
On sponges (Halichondria panacea and Hymeniacidon perleve ), particularly where associated with Lomentaria, Corallina and other fine red algae; from LWST to 100 m. Most abundant in March and August- September.
Distributed from Azores and Mediterranean to Norway (Distr. C. tubercularis).