Large (up to 110 mm in length), with seven teleoconch whorls. Protoconch of about two and one-half volutions, angulate to rounded on sides, varying in diameter from about 1 to 1.5 mm, top flattened, ending at small, straight varix.
Spiral ornamentation on first two teleoconch whorls masked by axial ribs, made apparent only by two small spines on each rib. By third whorl a strong secondary spiral cord between two major cords and numerous tertiary threads developed between major cords and on subsutural ramp. Body whorl with alternating spiral cords of three orders of magnitude in variable arrangement. Siphonal canal with regularly alternating major and minor cords.
Axial ornamentation on first teleoconch whorl of nine angulate ribs bearing two open spines on each; apically directed, one at shoulder stronger, second near suture. On second whorl, every third rib strengthened to form varix with very long, apically directed shoulder spine; intermediate ribs reduced to nodules on spiral cords. Subsequent whorls with no intervarical ornamentation except strong growth lamellae sinuated by spiral ornamentation, giving a malleated appearance to intervarical areas. Three low, rounded varices per whorl, each with long, sharp spines; three primary spines at shoulder, periphery, and base of varices on body whorl, spine at shoulder always directed somewhat apically. Shoulder spine, in some specimens nearly vertical and exceedingly long, and, in these specimens peripheral spine usually recurved apically and equally long. Shorter-spined examples with peripheral spine nearly horizontal. Anterior-most spine always long, nearly straight and directed horizontally; in short-spined individuals basal spine longest on body whorl. Alternating with primary spines are three shorter, narrower, adaperturally-recurved secondary spines. Siphonal canal with five or six adaperturally-recurved primary spines alternating with secondary spines; second primary spine from body whorl always longest spine on shell, others decreasing in length anteriorly. Secondary spines short, sharp, tending adaperturally at an angle to major spines, angle increasing anteriorly; posterior-most secondary spine almost parallel with adjacent primary spines but anterior-most at angle greater than 90 degrees.
Suture impressed, crossed diagonally by fine growth lamellae, directed adaperturally at posterior end.
Aperture ovate; no true outer lip, apertural edge of varix scalloped into spines as series of deep notches, their size corresponding to strength of spines. Notches result in series of tooth-like projections in advance of varix, proj ection posterior to spine at base of body whorl elongated into large labral tooth. Strong anal notch formed by projecting edge of subsutural ramp and appressed portion of inner lip, extending above suture to level of periphery of preceding whorl. Anterior two-thirds of inner lip freestanding, narrow, smooth.
Siphonal canal long; terminations of previous canals fused into tube, open by narrow slit, spines extending almost to slightly recurved distal end of canal.
Colour creamv white, maculated with light tan blotches, most deeply coloured in interspaces between spirals, but with growth lamellae lighter in colour causing spirals to have appearance of elongated nodes; aperture and interior of shell white. Operculum reddish brown; subterminal nucleus, with eight to ten strong concentric ridges, strongly creased along median line.

The shell of this species is similar to that of M. scolopax but can be readily distinguished by the malleated surface and pale primary spiral cords.
The length of the spines in this species and the size of the shell appears to be correlated with depth and sediment. The larger, shortest spined specimen came from a sand habitat at low tide, the other intertidal specimen was collected in muddy sand. The smaller, longer spined specimens were collected in deeper water on muddy sediment.

North-West and Northern Australia. Coleman (1975) states that this species feeds mainly on bivalves and (Coleman, 1981: 58) lays its egg capsules as a column fixed to a suitable base anchored in sand.