Type species: A. arctica McIntosh, 1879 Generic rediagnosis. Body long and thin. Ventral groove along whole length of body. Prostomium bluntly rounded to conical with small palpode, peristomium indistinct. Eyes absent.
Anterior parapodia button shaped with long, bent chaetae arranged in tufts. Parapodia embedded into lateral groove in median region, becoming more distinct in posterior region. Parapodia with branchiae in third quarter of body. Posterior chaetae longer than median ones, stiff and straight. All chaetae simple.
Branchiae flat, wide at base, tapering to top.
Posterior end of body laterally flattened with chaetigers reduced in length. Pygidium with or without anal tube. Anal tube, if present, with or without ventral cirrus.