Body thick, soft. Tentacles numerous, long and thick. Upper lip rounded trapezoidal. Prostomium ventrally conspicuous, cushion-like. Many eyespots dorsally and laterally behind the tentacles. Three pairs of dichotomous gills (on segments 2-4) with very short tips. Anterior gills large, rounded with long stems, middle ones smaller with shorter stems, posterior ones smaller than the middle ones. Lateral lobes on segments 2-4. 14-15 ventral shields on the thorax. Notopodial chaetae from segment 4. Seventeen chaetigerous thoracic segments. Uncinigerous tori from segment 5. Uncini in double rows on segments 11-20. Pygidium with smooth or finely papillose edge. Notopodial chaetae smooth, with narrow brims. Uncini with one big and several smaller teeth.
Up to 175 mm for 100 segments.
Fragile, encrusted with sand or mud.
In life yellowish red, reddish, or brown with white spots on the body, tentacles pink and whitish, gills red with white spots. In alcohol pale yellow or greyish.
On all kinds of level bottoms: clay, silt, fine and coarse sand and also on some types of hard bottoms; eulittoral to about 500 m; euhaline waters.
Eastern North Atlantic, Mediterranean, South America, Red Sea, Persian Gulf, Indian Ocean, Australia, Kerguelen, Japan. Entire Norwegian coast, Swedish west coast, Kattegat, Shetland, Scottish east coast.