Body long, thick, conical with 7 thoracic chaetigers. 30-40 pairs of radioli, basally connected with a thick membrane; highest ventrally. Peristomium with 2 eyes.
Operculum funnel-shaped with radial grooves and 20-40 marginal serrations. Peduncle without spines.
Collar dorsally and laterally incised and curved backwards ventrally. Thoracic membrane wide (S. vermicularis-lateral view).
First chaetiger with thin, fine denticulate, capillaries, and stronger, slightly bent, chaetae, with a finely denticulate tip and 2 large teeth at the base of the tip. Notopodial chaetae on other thoracic segments are broadly winged and denticulated at the tip. Thoracic uncini with 5-6 strong teeth. Abdominal neuropodia bear flat-trumpet chaetae. On the most posterior segments, they are replaced by long, thin, capillaries. Abdominal uncini with 4-8 teeth. No apomatus-chaetae (S. vermicularis-chaetae).
Up to 70 mm long for 300 chaetigers.
With 5 longitudinal ridges cut into blunt teeth or sharp spines, or with transverse growth-ridges, but fairly smooth when erect and aggregated (S. vermicularis-tubes). Colour pink to pale red, rarely white; 50-70 mm long, 4 mm in diameter.
Abdomen yellowish or reddish. Crown with red or white cross-bands. Operculum banded red-white.
On rocks and shell; sublittoral in lagoons, inlets, fjords, and natural harbours.
World-wide, English Channel, whole North Sea, Skagerrak, Kattegat, the Belts and northern Öresund.