Body relatively large and strong.
Prostomium semicircular with two reddish eyes, placed laterally in front of the prostomium. Prostomium with 3 antennae and 2 simple palps.
Median antenna a little longer than the lateral ones, inserted in the middle of the prostomium. Lateral antennae and palps as long as or a little longer than the prostomium.
6 pairs of simple tentacular cirri on 3 segments.
Dorsal tentacular cirri of second segment the longest, almost twice as long as the median antenna. Dorsal and ventral cirri simple.
Dorsal cirri often longer than the longest tentacular cirri. Ventral cirri a little longer than the parapodial lobes.
Dorsal lobe of parapodium with only one typical simple upper chaeta (sickle-shaped with more than 10 very long fine teeth) and up to 12 compound and 2 simple lower chaetae.
Blades of compound chaetae of different sizes, finely serrated and bidentate.
Simple chaetae present in upper and lower neuropodia, serrated at one side and bidentate tips (M. similis-detail).
Pygidial plate broad and rounded, with a fringed edge, consisting of elongated simple or bilobed papillae.
Body up to 18 mm for 65 segments.
Upper eulittoral to 20 m.
Mediterranean, North Sea.