Body anteriorly and posteriorly tapered. Prostomium rounded to triangular, about as long as broad. Median antenna of similar size and shape as paired ones, inserted anterior to eyes. Eyes medium-sized. Proboscis almost smooth, with sparsely distributed minute papillae (often not discernible on preserved specimens), arranged in more or less distinct rows. Terminal ring of about 16-20 papillae. Tentacular cirri of segment 1 reaching about segment 4. Dorsal tentacular cirri of segments 2 and 3 reaching about segments 8-10. Ventral tentacular cirri reaching about segments 5-6, cylindrical or flattened to a varying degree. Chaetae present from segment 2, arising from anterior side of the cirrophores. Dorsal cirri of median segments broadly lanceolate, longer than wide. Parapodial lobes rounded, slightly bilobed, with a rather large number of chaetae. Terminal end of chaetal shaft with few, large teeth. Blades long and slender. Ventral cirri distally rounded, slightly longer than parapodial lobes. Pygidial cirri variable in shape, about 3-5 times as long as broad, cylindrical or slightly flattened. One band of cilia per segment, both dorsal and ventral.
Up to 90 mm for 140 segments.
Living animals often yellowish green, but brown and reddish specimens also occur. Brown pigment spots more or less dense on the prostomium, the dorsum and on the dorsal and ventral cirri. White iridescent pigment usually present dorsally on the posterior part of the prostomium, on segment 2, and may also occur as a mid-dorsal longitudinal band. Eyes red. Preserved animals light to dark brown.
Common on rock, stony gravel, shell gravel and sand. Intertidal to at least 50 m. In Dutch estuaries together with Lanice conchilega .
Recorded from all over the world except Arctic and Antarctic.