(O.M. Müller, 1806)
Body relatively slender.
Prostomium narrowly conical and taperings at both ends, with four eyes in a trapezoid arrangement, without a median antenna. Triangular caruncle reaching chaetiger 2 or 3.
Notopodial postchaetal lobes in segment 1 small and oval, in the following segments long and lanceolate and fused to the gills to more than half their length, in posterior segments becoming shorter and almost fully separate. Neuropodial postchaetal lobes in anterior segments short and rounded, from segment 18-20 onwards weakly bilobed.
Gills start at segment 2, cirriform and longer than the notopodial postchaetal lobes. Absent on the last 7 segments.
Anterior parapodia with capillary chaetae only, from neuropodium 26-40 and from notopodium 60-65 onwards also hooded hooks present. These usually bidentate, sometimes unidentate or with two small accessory teeth (S. squamata-detail).
Pygidium with a single lobe.
Up to 138 mm for over 200 segments.
Mid- to lower shore in clean or slightly muddy sand on exposed beaches, in 40 cm deep burrows in the sediment. Burrows supported by mucus. Can also swim freely, with snake-like movements.
North Sea to Öresund, perhaps world-wide except Arctic and Antarctic.