(O.F. Müller, 1776)
Body long; thorax cylindrical, abdomen tapering.
Tentacles numerous, thin, moderately long. Upper lip broad, rounded. Buccal segment ventrally forming a prominent, broad plate with a distinct median anterior notch. No eyespots.
One or two pairs of gills (on segments 2 and/or 3). Gills arborescent. Right and left gills often unequally developed, larger gills of segment 3 usually on opposite side of that of segment 2. When well developed, each gill with a long, round stem and (in contracted state) a pompom-like mass of branches. Lateral lobes on segments 2-4, those on segment 3 most prominent. Ventral shields on 17-20 segments. Notopodial chaetae from segment 4. Seventeen thoracic segments with chaetae. Uncinigerous tori from segment 5. Uncini in double rows on segments 11-19. Notopodial chaetae smooth, of various lengths, with brims. Uncini with one big and several smaller teeth, in anterior segments with prolonged posterior bases.
Pygidium without appendages, smooth.
up to 100 mm for over 100 segments.
A thin layer of secretion covered with a thick, relatively firm and brittle incrustation of clay and fine sand.
In life reddish to brown, gills brown. In alcohol pale yellow to reddish.
on mud, clay, fine and coarse sand, sand with gravel and shells, and mixed bottoms; upper sublittoral to about 4000 m.
Eastern North Atlantic to Madeira, Mediterranean, Canadian Arctic, North American Atlantic, Gulf of Mexico, South America, Novaya Zemlya, Bering Sea, Sea of Okhotsk, Japan Sea, North American Pacific, South Africa, Antarctic; Svalbard, Iceland, the Faeroes, Shetland, entire Norwegian coast, North Sea, Skagerrak, Kattegat, the Öresund.