Shell up to 100 mm (4 inches) in length, fusiformly-elongate but occasionally fusiformly-ovate, moderately solid. Whorls 9-10 apart from protoconch, spire whorls almost flat-sided or very slightly convex, sutures occasionally irregular, particularly on the body whorl. Sculptured with minutely pitted or macroscopically striate, shallow spiral grooves which usually become obsolete on the centre of the body whorl; spiral grooves number up to 15 on the penultimate and up to 25 on the body whorl, base of shell with 6-10 oblique cords. Some of the spiral grooves are orange-brown and appear as wide-spaced grooves; in some individuals the postnuclear whorls develop rather deep grooves which give rise to flat spiral cords which may persist to the sutural area of the body whorl. In some specimens, macroscopically fine longitudinal striae are visible. Aperture variable in length but usually short, 37-45% of total shell-length, narrow or moderately open, smooth within; outer lip slightly thickened and simple, and occasionally prominently convex. Parietal wall glazed, columella calloused anteriorly and with 4 or 5 prominent, oblique folds; siphonal fasciole short and usually with a calloused twist, siphonal notch distinct. Flesh, fawn, tan or light orange-brown in colour, usually ornamented with nebulous, narrow, dark brown axial streaks, and wide-spaced, dark orange-brown spiral lines; the aperture and columella are either light orange-brown or the margin of the aperture is orange-brown, the interior is pale greyish-white and the columellar folds are whitish.

The species superficially resembles M. chalybeia Reeve, but differs in colouring and the appreciably shorter aperture. M. declivis Reeve, which is more frequently encountered in South Australia, is shorter and more compact, the grooves are deeper and give rise to flat spiral cords.

New South Wales to Tasmania and Western Australia.
In sand pools and on a coral reef substratum, from the intertidal zone to a depth of 30 fathoms.s to Tasmania and Western Australia.