(Montagu, 1803)
Description (shell):
Adult shell is a curved, glossy, strongly annulate tube. The radius of the curvature varies with age. In animals up to 1.0 mm long the apex is spirally curved, in larger animals the spiral part is lost. Apex is sealed by an eccentrically pointed, calcareous plug. Aperture is circular, with a thickened rim.
Size:
Up to 4 x 0.5 mm.
Colour:
Yellow-brown or white.
Animal:
Snout flat, deeply bifid; cephalic tentacles long, with setose tips. No pallial tentacles. Operculum thick, flat, circular; polygyrous with a central nucleus.
Habitat:
Sublittoral, on sand and sandy-mud, to 250 m.
Distribution:
Distributed from Mediterranean to south-west coasts of British Isles (Distr. C. trachea). Common, but inconspicuous.