(Audouin & Milne-Edwards, 1834)
Body elongated, thin and fragile.
Prostomium rounded, with four eyes in a trapezoid arrangement sometimes with two ocelli. It is divided into three parts by an Y-shaped groove. Palps often longer than prostomium. Median antenna longer than lateral antennae. Lateral antennae a little longer than the peristomium. Tentacular segment with a weakly developed occipital flap extending forwards across the prostomium.
Dorsal tentacular cirri longer than antennae and segment width, ventral much shorter. Dorsal cirri cylindrical, smooth, alternating in length; those of first chaetiger much longer than the following ones. Ventral cirri short and triangular.
Two bud-shaped aciculae. Blades of compound chaetae very short, bidentate. In middle and posterior parapodia a simple chaeta is present in the upper bundle.
Pharynx very short, with 6 or 7 large teeth, curving rearwards between two lateral folds (O. fulgurans-detail). Proventriculus three times as long as broad.
Body up to 40 mm long for 100 segments.
Yellowish-white, reddish or orange.
North Atlantic up to Mediterranean, English Channel up to Straight of Dover.