Body slender, prostomium long and narrow pointed at both ends. With four eyes in a horizontal row or without eyes; without antenna. Caruncle ending in a free tip, reaching chaetiger 1 or 2.
Notopodial postchaetal lobes in chaetiger 1 short and rounded, in the following chaetigers long, lanceolate, almost as long as and fused to the gills, except for the tips. Gills start at segment 2 and are present almost to the posterior end.
Neuropodial postchaetal lobes in anterior segments short and rounded, from chaetiger 30 onwards bilobed.
Anterior parapodia with capillary chaetae only, from neuropodium 25-36 and from notopodium 55 onwards also hooded hooks present. These unidentate or with a small accessory tooth (S. bonnieri-detail).
Pygidium with a single lobe.
Up to 60 mm for 90 segments.
On sand and oysterbanks, from eulittoral to 50 m.
Northeast Atlantic, English Channel, North Sea, Skagerrak.