Body elongated, oval, strongly tapering at both ends.
Prostomium indistinct, with small papillae and four filamentous antennae.
The first segment is papillated, with a pair of filamentous tentacular cirri, two eyes and a papilla-like median antenna.
Following segments dorsally with a transverse row of 2-9 big tubercles and two rows of smaller papillae.
Parapodia conical, with three terminal tubercles and up to 8 chaetae with smooth falciger blades and a finger-like ventral cirrus (S. baltica-detail).
Pygidium with 2 round cirri.
Up to 2.2 mm long for 16 segments.
Living animal yellow to brown.
On sand and mud, 6-20 m deep, also in brackish water. Burrows in sediment, not swimming freely, like may other species of the family.
North Sea, Öresund, Baltic Sea.