Body short, with triannulate segments. Epidermis reticulate with a regtangular pattern. Ventral side without an obvious furrow.
Prostomium small and bilobed, with 2 long, dorsolatteral nuchal slits. Eyes absent.
Noto- and neuropodia simple mounds, each with a bundle of capillary and forked chaetae. Dorsal and ventral cirri absent.
Four to six pairs of arborescent gills, starting at notopodium 2.
Pygidium short, cylindrical.
Up to 40 mm for 40 segments, when contracted; twice as long when extended.
In alcohol yellow to colourless.
On mud and mixed bottoms, from the upper sublittoral to over 2000 m. It lives in U-shaped burrows which are supported by slimy secretions.
Arctic, North Atlantic to Mediterranean, North Sea to Öresund, South Africa.