Diagnostic characters
Shell harp-shaped in profile, the last whorl occupying most of the shell; spire small. Aperture long, narrow, slightly sigmoid. Shell covered by mantle lobes when animal is active. No operculum on foot.

Other characters
The shell is slightly translucent and glossy. There are four whorls, those in the spire nearly flat-sided, with extremely shallow sutures; the apex is truncated. The sole ornament is a series of fine and irregular growth lines. The aperture has parallel sides and ends basally in a canal. The outer lip is thick, inturned, and has 15-18 ridge-like teeth on its inner edge. The columella is short and marked by three folds; there is no true inner lip, but it is functionally replaced by a row of about twelve tubercles on the last whorl. White, sometimes brownish basally and pink along the lip. Up to 12 mm high, 7-8 mm broad; last whorl occupies 80-85% of shell height, aperture 75-80%.
The head ends in a fold from which the tentacles arise, each with a basal eye; the mouth of the introvert lies under the fold. The mantle edge is drawn out anteriorly to form a siphon lodged in the basal canal, while laterally it forms lobes which cover the shell during activity but are withdrawn if the animal is disturbed. They bear tubercles on their outer side. The male has a penis; the foot is long and narrow. The flesh is white, generously speckled with brown, red, orange, and yellow; the mantle lobes are often dark, their tubercles yellow. The tentacles have a central yellow line and are pale at their tips and base.
£. valuta occurs from the Mediterranean to Norway and is found at depths of 20-100 m off most shores of the British Isles (except between the Humber and the Isle of Wight) wherever the bottom is hard. It associates with ascidians, which form its food (Fretter, 1951a).
The larval stage is an echinospira (p. 316) with 3-4 whorls coiled helically; the coiling of the inner shell is not coaxial with that of the outer (Lebour, 1933a,1935a).