Shell up to 43 mm (about 1,75 inches) in length, cylindrically elongated, solid, both whorl long, sutures weak and sharply incised. Whorls 6,5-8, apart from a protoconch of 2 smooth nuclear whorls, spire whorls convex and occasionally weakly shouldered at the sutures, body whorl frequently inflated; sculptured with line spiral grooves which produce narrow spiral threads which number from 7-13 on the penultimate and from 14-23 on the body whorl, apart from 10-14 wider spaced basal cords. Under magnification, very fine longitudinal hairlines are visible. Aperture longer than the spire, narrow and smooth within, outer lip appreciably less thickened than in M. paupercula, convex or angulate anteriorly, interior swelling weak, margin of outer lip smooth or obsoletely crenulate anteriorly. Columella calloused, and with 4-5 oblique folds, siphonal fasciole straight, siphonal notch distinct. Light to dark chocolate-brown in colour, ornamented with narrow and close-set, slightly wavy white axial lines; aperture brown near the margin, interior bluish-white, columella brown, folds bluish-white. Periostracum thin, brown and moderately translucent.

The species is similar to S. paupercula (Linnaeus), but differs in being more slender and cylindrical in form, the body whorl is longer, the interior callus of the outer lip is weak and the spiral sculpture is continuous from the spire whorls to the base.

Range: Mauritius to New Guinea and the Ryukyu Islands. On reefs, under rocks, in the intertidal zone.