Body long and thin.
Prostomium semicircular, sligthly pointed at the tip and broader than long; with four eyes in a trapezoid arrangement; without ocelli. Palps longer than the prostomium, not fused. Lateral antennae longer than the palps, with 8 to 18 rings. Median antenna longer than lateral antennae.
Antennae, tentacular cirri and dorsal cirri all annulated. Dorsal tentacular cirri still longer; ventral tentacular cirri somewhat shorter than lateral antennae.
Dorsal cirri alternating: longer, with 10-16 rings and shorter, with 7-10 rings. Ventral cirri elongate oval, shorter than parapodial lobes.
Anterior and posterior parapodia with compound chaetae with serrate, bidentate blades. Posterior parapodia bear also simple chaetae, which are weakly bent, bidentate at the tip and finely denticulate along the edge. Mid-body parapodia 2 or 3 thick Y-shaped chaetae. Usually three aciculae.
Pharynx long, with an anterior tooth.
Two pygidial cirri and a little tail.
Up to 50 mm for numerous segments.
Colourless to yellow, often with fine transverse banding.
On all substrata; eulittoral to 400 m. Also in poly- and euhaline water. Under stones, shells and among seaweeds, sponges and hydroids.
English Channel, southern North Sea to Helgoland.