Shell small, elongate, flattened, equivalve, white rounded in front, squarely truncated behind, umbo about two-fifths from the posterior end. A low ridge extends from the umbo to the posterio-ventral margin, over which the sculpture is bent. The ornament consists of about eighteen concentric ridges, separated by spaces usually wider than the ridges. The two tooth-like ridges are very similar in each valve.
Length 6 mm Depth 3.5 mm Conjoined valves would be about 2 mm.
Type, with five others, all single valves, from 40 fathom off Thouin Bay. It has a very distant affinity with M. albida Ten.-Woods.