Body long, anteriorly cylindrical, posteriorly slightly flattened.
Prostomium composed of 8-10 rings, with palps and antennae forming a cross at the tip.
Anterior 33-37 parapodia uniramous with two prechaetal lamellae, a somewhat longer postchaetal lamella and finger-like dorsal and ventral cirri. Following segments until segment 80-85 with gradually developing notopodia. Posterior parapodia biramous with a small notopodium with a prechaetal lamella and a somewhat shorter, rounded postchaetal lamella. Posterior neuropodia with prechaetal and short and broad, distally pointed postchaetal lamellae. Dorsal and ventral cirri cirriform.
Notopodial chaetae numerous, long, bent capillaries. Neuropodial chaetae compound with long, denticulate blades.
Pharynx with numerous flat papillae.
Macrognaths with 3-6 teeth. 25-50 X-shaped micrognaths in a full circle. 15-21 chevrons on each side.
Up to 300 mm long for 300 segments. 9 mm broad.
Preserved specimens yellowish grey to dark brown.
Northern North Sea and Skagerrak, Arctic, North Atlantic, Mediterranean, Adriatic.