Shell wide (for the genus), spire straight sided, whorls evenly convex, aperture about 1/3 of shell length; protoconch of 1 1/8 - 1 1/3 smooth whorls. Spiral sculpture of cords on base; axial sculpture absent. Outer lip sinuous in profile, with shallow sinus; lip thickened externally; thickened internally, with 5-7 denticles. Columella callus sharp-edged in mature shells, axial ridge inside edge bearing several denticles. Siphonal canal very short. Colour variable, but several predominant patterns; (a) uniformly white or fawn (b) broad spiral brown bands on a white background (c) zigzag brown lines (d) axial brown flames (e) white spots more or less in quincunx pattern on a tan background. Interior white or fawn. Periostracum smooth.
Size: Up to 10 mm in length.

M. tenuis is identical in shape but larger, and often with a similar colour pattern. M. lincolnensis is the same size and sometimes has a similar colour pattern, but has flat whorls. M. tayloriana is about the same size, has similarly rounded whorls, and can only be separated by its fairly constant colour pattern.
This species is extremely variable in colour pattern. When selecting the specimen to illustrate it was impossible to find a completely representative specimen, as the range of colour and pattern variation is so large. Identification of a specimen lot, with many shells from the same locality, is more feasible, particularly if shells of the badia or dictua colour patterns are present, as these two patterns do not occur in the other species. A transition within the lot from these distinctive patterns to patterns shared with other species can usually be seen.

Endemic to Australia; Port Stephens, NSW, around southern Australia to south-western WA.
Habitat: Intertidal on algae on rocky shores.