Shell up to 20 mm (about 0,75 inches) in length, rather ovate and solid, body whorl moderately long, sutures distinct but narrowly incised. Whorls 5-6, apart from 1,5-2 cream-coloured, smooth nuclear whorls, spire whorls regularly convex, sculptured with finely punctate spiral striae which number from 3-6 on the penultimate and from 5-14 on the body whorl, apart from the 8-11 oblique basal cords; in some specimens the spiral striae are confined to the shoulder of the body whorl, the centre is smooth and then the cords continue towards the base. Aperture longer than the spire, very narrow and smooth within, outer lip prominently thickened, smooth apart from 2-3 weak crenulations anteriorly, outer lip with a prominent, bluntly triangular and moderately long callus. Columella concave, with a weak callus-shield anteriorly and 4 or 5 prominent, oblique folds, parietal wall only glazed and posteriorly with a calloused ridge or pad; siphonal fasciole short and straight, siphonal notch moderately shallow. Fresh specimens are dark brown or reddish-brown in colour, ornamented with a pale, whitish or yellowish spiral band which usually has superimposed small white spots; on the spire whorls this band adjoins the sutures while on the body whorl it is in line with the start of the aperture; on the lower two-thirds of the body whorl are few or moderately numerous small white spots distributed at random or sometimes longitudinally aligned. The aperture and columellar folds are bluish-white or light violet and the parietal wall is brown. The periostracum is thin, orange-brown and moderately translucent.

This species has been confused with M. auriculoides of authors, a species which will have to hear the name M, assimilis Pease. M. auriculoides Reeve, a rare species, is squatter and broader than M. assimilis; the body whorl is shorter and the outer lip has a prominent, more or less triangular interior callosity and a smooth outer lip margin, apart from 2-4 rather obsolete denticles anteriorly. Reeve's species has probably been based on the Indian Ocean form of the species, which lias a dark brown shell with white spiral lines which have only a very slight indication of being spotted with white; the anterior part of the body whorl has only a minimum of small white spots. In the Pacific Ocean form turturina Souverbie, the white spiral lines become faint and are overlaid by more prominent, white or yellowish spots and the anterior part of the body whorl is prominently spotted. M. auriculoides and M. assimilis are sympatric in several Indo-Pacific localities without any intergrades having been encountered. The difference in apertural features between the two species are of the same magnitude as between M. litterata and M. retusa. M. auriculoides has a smooth outer lip, whereas M. assimilis has an outer lip that is minutely denticulate along its entire length.

Mauritius to Polynesia. On reefs, under rocks and coral, in the intertidal zone.