A scale-worm with a body of uniform width. Dorsal and ventral surfaces smooth.
Prostomium bilobed, with a peak on each lobe, a median antenna, a pair of lateral antennae, ventrally inserted, and a pair of palps. Two pairs of eyes, the anterior pair near the prostomial peaks, the posterior pair near the rear margin. First segment bearing chaetae and a pair of dorsal and ventral tentacular cirri. Scales overlap, covering the body. The first pair of scales are round, the rest oval to kidney-shaped, about a quarter of the margins fringed with small papillae, the surfaces with small tubercles and sometimes a row of more distinct tubercles on the outer border.
Notopodia are small mounds with a ventral acicular ligule and abundant chaetae. Notopodial chaetae spinose with blunt tips.
Neuropodia well developed with an anterior acicular ligule and chaetae. Neuropodial chaetae spinose with bidentate tips, a few in upper and lower positions with unidentate tips
Up to 65 mm for 39 chaetigers.
Variable, from yellow to black, with plain or patterned scales.
Littoral on rocky shores. Sublittoral to 230 m on varied bottoms. Sometimes found in tubes of other polychaetes. Has been recorded from brackish water in estuaries.
Northern hemispher; whole North Sea, Skagerrak, Kattegat, Öresund, Belts and Baltic Sea to southern Finland.