(Delle Chiaje, 1822)
Animal with a long, relatively broad body, sligthly tapering at both ends.
Prostomium, short and very broad, with 4 eyes. Anterior pair of eyes larger than posterior pair; with lenses. 3 antennae and 2 palps present. Palps thicker and a little longer than the lateral antennae and with two rings. Lateral antennae thread-like and a longer than the prostomium. Median antenna half the length of the lateral antennae and placed on the anterior edge of the prostomium.
First 3 segments with 6 pairs of long, annulated tentacular cirri. Tentacular cirri placed on long cirrophores. Tentacular cirri sligthly shorter than dorsal cirri.
Parapodia biramous. Dorsal cirri annulated and much longer than the parapodia; ventral cirri finger-shaped, as long as the neuropodia.
Notopodia with 1 acicula. Neuropodia with 1 or 2 aciculae and some branched dorsal chaetae. Ventral bidentate compound chaetae numerous.
Pharynx without papillae or jaws.
Body up to 70 mm for 55-60 segments.
Dorsal more or less chestnut-brown, with four fine white or bluish, yellowish with dark cross-lines. Prostomium white with red or brownish eyes. Cirri white-brown annulated. Ventral side of the body yellowish or brownish, with light median lateral line.
Mostly found on muddy bottoms, moving swiftly in a snake-like manner. Also found on sandy bottoms between shells and holdfasts of seaweeds. Down to 200 m.
North Atlantic, Mediterranean, English Channel, North Sea, Skagerrak, Kattegat up to Öresund.