(Linnaeus, 1758)
Description:
Body twisted left, with 3 thoracic segments.
Opercular plate very oblique, concave with shallow talon towards lower edge. About 9 radioli. Tips of radioli not much longer than adjacent side-branches. Collar asymmetrical forming a large 'hinged' flap at dorso-convex margin. First chaetiger with a single thin and smooth capillary on two collar chaetae on the notopodia. Collar chaetae geniculate with a group of large teeth below the knee and small teeth subdistally. First chaetiger without ventral tori. Second and 3rd thoracic segments with capillaries and the 3rd segment also with Apomatus-chaetae. Two pairs of ventral tori with uncini; with 4 rows of teeth. Abdominal neuropodial chaetae strongly geniculate and coarsely toothed along the distal part. Tori with uncini which resemble those on the thoracic (S. spirorbis-chaetae).
Size:
Up to 6.5 mm for 35 chaetigers.
Tube:
About 3 mm across, evenly coiled, shiny, and with a small peripheral flange.
Colour:
Body greenish with brown stomach.
Habitat:
On Fucus, especially Fucus serratus , occasionally on other algae, e.g. Laminaria and Himanthalia buttons, and stone; intertidal and shallow water.
Distribution:
Arctic, North Atlantic, English Channel, whole North Sea, Skagerrak. Uncertain from Kattegat, the Belts, Öresund and Baltic Sea.