Body long and vermiform with 24-27 segments.
Prostomium broadly rounded, without eyes. Body scattered with small papillae. Palps club-shaped, not much longer than the prostomium.
Peristomium dorsally not visible, but laterally clearly separated from the 2nd segment.
4 pairs of thread-like gills on segments 2-5, clearly longer than the segment width.
Ventral chaetae from the 3rd segment, dorsal chaetae from the 5th segment. The anterior notopodia bear two capillary chaetae; anterior neuropodia with a single compound chaeta with a curved blade, some with a simple hook with a small lamella. Following neuropodia with two chaetae. (M. helgolandica-chaetae).
Interramal papillae present.
Pygidium posteriorly weakly incised with 1 ring of about 10 small papillae.
Up to 3.3 mm for 24-27 segments.
Preserved specimens whitish.
On sand, between 19 and 25 m.
Southern North Sea and Helgoland, Skagerrak.