A sinistral, glossy and solid shell with a tall, cyrtoconoid spire and a small aperture with a basal siphonal notch. There are about 15 whorls of which four belong to the protoconch. The whorls are nearly flat-sided; sutures are shallow. The last whorl has three tuberculated ridges plus 2-3 basal ones which are smooth or slightly nodose. The tubercles near the outer lip are axially elongated. In the spire the more basal whorls have three tuberculated ridges, but the number falls to two, then one, towards the apex. There are about 20-23 costae on the last whorl and about two less on each successive whorl up the spire. The whorls of the protoconch have fine transverse lines which cross 1-2 spiral ones. Last whorl occupies about one third of the shell height, the aperture a fifth to a quarter.
Up to 7 x 2 mm.
The head has a short snout with the opening of the introvert on its underside. The tentacles are long and slender, each with a basal eye. A short siphon arises from the mantle edge on the right. The pallial organs are reversed in position because of the animal’s sinistrality, with the gills on the right and anus and genital duct on the left. The male has no penis. Body colour is white, but tentacles have yellow marks.
Lives on sponges, especially Hymeniacidon and Halichondria , are often partly embedded in them and feed off them. May also be found under stones or on algae near LWST and to about 100 m deep.
From Spain to Norway and penetrates the Baltic as far as Kiel (Distr. C. pallescens).