M. Sars, 1856
Thorax cylindrical, abdomen tapering towards the pygidium.
Prostomium with 2 lappets and with 2 eyespots.
Gills short, groups well separated. Three gills of each group with fused bases, the fourth one free and a little behind the three.
Collar chaetae fine and short, smaller than normal notopodial chaetae. Fourteen thoracic segments with notopodia with capillary chaetae, the posterior eleven ones also with neuropodia with uncini. Twelve uncinigerous abdominal segments. Uncini with two rows of teeth with 4-7 teeth in each row. Posterior thoracic and all abdominal segments with a small cirrus at upper edge of each neuropodium.
Pygidium with two lateral cirri (S. borealis-detail).
Up to 50 mm long.
A thin layer of secretion encrusted with mud.
In life pale with greenish gills. In alcohol yellowish pink to yellowish grey.
On silt and mixed bottoms; 30-350 m.
West Greenland, Labrador, Canadian Arctic, Siberian Arctic, Bering Sea, Canadian Pacific. East Greenland, Svalbard, Iceland, Norwegian coast from Varanger to Møre.