Body long and thick, anterior part straight, posterior part usually rolling up in a helix. Tentacles moderately numerous and long, thick. Upper lip broad. Eyespots present or absent. Three paired series of gills (on segments 2-4), each series consisting of a number of free filaments. Segment 2 with at least seven filaments on each side, segments 3 and 4 with at least four filaments on each side. No lateral lobes. Segments 2-4 ventrally cushion-like, with longitudinal folds, the following ca. 10 segments with ventral shields. Notopodial chaetae smooth, or two lengths, on long parapodia starting at segment 2 and in a highly variable number of segments (up to 90). Thorax and abdomen not discernible as such. Uncinigerous tori from segment 5, relatively short. Pygidium with small papillae.
Worm up to 80 mm long.
A thin secretion lining encrusted with mud and wound in a more or less regular helix.
In life yellowish, gills red. In alcohol pale yellow or whitish.
Mainly on mixed bottoms of mud or clay with sand. Vertical distribution 15-650 m.
Eastern Atlantic to the Gulf of Guinea, Mediterranean, Sea of Okhotsk, Aleutian Islands, North American Pacific, southern Chile, South Georgia, Shetland, southern Norway to Trondheimfjord, Tromsö, North Sea, Skagerrak, Kattegat, Swedish west coast.