Shell elongate, narrow, with a well developed spire, colour yellowish-white, apex blunt and rounded; whorls 3, hollowed above; smooth at first, but small, wrinkle-like ribs develop and become more prominent on the body whorl; they extend from the shoulder, and fade away before reaching the centre of the body whorl. Aperture narrow above, widening rapidly towards the front; outer lip sinuous, moderately thickened, unarmed Columella excavate, and bearing four ascending plaits, the upper three being much the stronger.
Length 7 mm Breadth 3.5 mm.
Type, with three others, from 15 fathoms, near George III. Reef, below Southport.
This is a near relative to M. formicula, Lamk., but it is much narrower, with a longer spire, much less strongly ribbed, and of a thin, delicate texture. My experience of M. formicula shows it to be a strictly littoral species, living between tide marks, whilst this form was from fairly deep water.