A scale-worm with a body of uniform width. Dorsal and ventral surfaces smooth.
Prostomium bilobed, without peaks, with a median antenna, a pair of lateral antennae, laterally inserted, and a pair of palps. Two pairs of eyes, the anterior pair in front of the line of greatest width, the posterior pair near the rear margin.
First segment bearing chaetae and a pair of dorsal and ventral tentacular cirri. Scales overlap, almost covering the body. The first pair of scales are round, the rest oval to kidney-shaped, the margins with sparsely distributed short papillae and the surfaces with small tubercles. Notopodia are small mounds with a ventral acicular ligule and chaetae. Notopodial chaetae spinose with blunt tips.
Neuropodia well developed with an anterior acicular ligule and chaetae. Neuropodial chaetae spinose on the terminal quarter, with bidentate tips, sometimes a few in lower position with unidentate tips (M. ljungmani-detail).
Up to 15 mm for 36 chaetigers.
Yellow to grey.
Littoral and sublittoral, usually on hard bottoms, occasionally in tubes of Chaetopterus variopedatus .
Eastern Atlantic between North Norway to the Mediterranean and Senegal, Adriatic, northern North Sea, Skagerrak, Kattegat, up to Öresund.