Shell elongate, turreted, slightly cyrtoconoid, with seven to nine tumid whorls; sutures deep, sinuous, with narrow, minutely granular subsutural band. Sculpture of strong costae, spiral striae, and fine growth lines. Costae rather narrow, slightly prosocline (especially on last whorl); about 11-12 on last whorl. Spiral striae narrow, slightly nodular where they cross costae, much reduced on subsutural band; 16-20 on last whorl, four to seven on penultimate. Protoconch of three or four whorls, finely reticulate, with distinctive diamond pattern. Aperture elongate-oval, with short siphonal canal and shallow, semicircular anal sinus. Outer lip thin, crenulate, without a varix though a costa often present at margin; a sharp inflexion at junction with siphonal canal; older shells with a row of nine teeth internally, first and last larger than rest (R. linearis-drawing).
Up to 12 x 7 mm.
Cream with lilac tinge to apex or light horn colour; spiral striae often darker horn coloured and visible through outer lip.
Diameter of cephalic tentacles reduces abruptly about half-way along length; eyes at this point. Siphon on mantle edge extends well beyond siphonal canal in active animals. Foot with double-edged anterior margin and recurved anterio-lateral horns; no operculum.
Occasionally under stones or in pools at LWST; more commonly sublittoral on sand, shell, and gravel bottoms at 10- 200 m.
Distributed from Mediterranean to northern Norway (Distr. R. linearis).