Body long, tapering posteriorly; dorsally convex, ventrally flat with a deep longitudinal furrow. Totally 82 segments; ten thoracic segments. Gills absent.
Tentacular ridge much folded, forming the two lateral lobes. Upper lip thin, flat, oval, forming the median lobe. Tentacles numerous and short, comprised of thin cylindrical ones and thick, distally dilated, furrowed ones. Lower lip prominent, cushion-like.
5-8 distinct, narrow ventral shields on thorax (from segment 2).
Notopodia cylindrical, very long. Notopodial chaetae barely projecting from notopodia, thin, very finely denticulate, starting at segment 2 (A. trilobata-detail). No neuropodial chaetae on thorax and the anterior 5-6 abdominal segments. Posterior part of abdomen with small neuropodia with spines. Pygidium with a smooth edge.
Up to 52 mm for 72 segments.
In life whitish, pink or mauve, tentacles pink. In alcohol whitish or greyish.
Mainly on mud mixed with sand; 24-2891 m.
Eastern North Atlantic, Mediterranean, Adriatic, New England continental slope, Japan, Solomon Islands, South Africa, Tanzania, Australia, Iceland, the Faeroes, Lofoten, Norwegian coast from Tromsö to Oslofjord, Skagerrak, Swedish west coast.