(Müller, 1776)
Description:
Shell oval in outline; to about 30 mm long. Some of the largest specimens have a truncated anterior. The external surfaces are smooth, save for concentric growth lines. The shell is endopunctate, white, yellowish or grey in colour. Pedicle foramen with small deltidial plates that do not join in the midline.
Internal:
Long loop, reflected ventrally; no median septum. Lophophore with long lateral lobes and a median spiral (M. cranium internal).
Habitat:
Sublittoral, from shallow water to 1262 metres.
Distribution:
It has been found around the Shetlands, Orkneys, along the western coasts, Western Approaches; Arctic to Mediterranean.