Body slender and small.
Prostomium semicircular to oval with two eyes, placed laterally in the middle of the prostomium. Prostomium with 3 antennae and 2 simple palps.
Median antenna longer than lateral ones, inserted in the posterior edge of the prostomium. Lateral antennae longer than the prostomium; palps a little shorter.
6 pairs of simple tentacular cirri on 3 segments.
Dorsal tentacular cirri all of about the same size, not much longer than the median antenna. Dorsal and ventral cirri simple.
Dorsal cirri clearly longer than longest tentacular cirri, ventral cirri not much shorter.
Notopodia represented only by the basis of the dorsal cirri with 1 acicula and 2-3 simple chaetae. Neuropodia with a long cirriform prechaetal process with 1 acicula and up to 8 compound chaetae. Dorsal chaetae of 2 types: one or two needle-shaped and slightly curved simple chaetae and one or two distally curved compound chaetae, with about 10 fine long teeth subdistally. Ventral chaetae predominantly compound, but in lower part of the bundle of posterior segments 1 or rarely 2 simple chaetae (M. listensis-detail).
Pygidial plate present, almost wig-shaped. Pharynx with 10 terminal ciliated papillae, without jaws.
Body up to 3 mm for 28 segments.
Transparent or whitish, intestines greenish.
Interstitial; eulittoral to upper sublittoral.
North Atlantic, North Sea, Skagerrak.