Body cylindrical, tapering posteriorly. Prostomium with three lobes, usually with two eyespots. Gills in two groups very close to each other at middorsum; first three gills of each group in a transverse row, the fourth just behind the middle one of the three.
12-16 stout, long chaetae with pointed tips on each side in front of gills.
Fourteen thoracic segments with normal notopodia with capillary chaetae, posterior twelve also with neuropodia with uncini. Thirteen or exceptionally 14 abdominal uncinigerous segments with small, rudimentary notopodia. Thoracic uncini usually with two vertical rows of teeth, 6-8 in each row, abdominal uncini with two or three vertical rows of teeth, 6-8 in each row (A. finmarchica-detail).
Pygidium with two long cirri and a number of small, round papillae.
Up to 50 mm long.
Thick and loose, straight cylindrical tube of mud and sand lined with a thin secretion.
In alcohol pale yellow.
On silt and mixed bottoms, rarely on pure sand; from the upper sublittoral to depths exceeding 5000 m.
North Atlantic, West Greenland, Quebec, Canadian Arctic, Siberian Arctic, Bering Sea, North American Pacific, Sea of Okhotsk, Japan Sea. East Greenland, Svalbard, Jan Mayen, entire Norwegian coast, Barents Sea, North Sea, Skagerrak, Swedish west coast, Öresund.