Holotype: length 13.6 mm, width 5.7 mm; Paratype: length 11.8 mm, width 5.2 mm.

Western Australia (Cockburn Sound) to the Palau Islands, Western Caroline Islands.

The shell is of moderate size (maximum length 14 mm) and lanceolate. The spire is high and acute, consisting of one and one-fourth nuclear whorls and five or six canted postnuclear whorls. The suture is moderately impressed and partially obscured by varical buttresses. The body whorl is moderately broad and much flattened. The aperture is small and ovate. The outer apertural lip is slightly erect and bears a series of five more or less prominent denticles on its inner surface. The columellar lip is smooth and adherent. The siphonal canal is moderately short, narrowly open, bent to the left, and dorsally recurved.
The body whorl bears four lateral varices, two of them more prominent. The earlier whorls each bear six varices, but the ventral and dorsal ones are reduced to buttresses in all but the first two postnuclear whorls. Spiral sculpture appears to be limited to the intritacalx, and consists of several broadly spaced grooves, these visible on the legding edge of each varix, and many faint spiral striae. The intritacalx also shows numerous axial striae that are much stronger than the spiral Bries, thus never producing the truly cancellate appearance of A. producta.
The shell is milk-white under the flat-white intritacalx and an almost transparent pale-brown periostracum. The radular dentition is composed of two typically muricine, sickle-shaped lateral teeth flanking a single five-cusped rachidian tooth, which in turn bears a central cusp, two laterals, and two intermediates, the lengths of which are in the ratio of 4:3:2. The two denticles at each extremity of the rachidian tooth, i.e. between the lateral cusp and the end of the tooth, are unique in the genus.
The operculum is typically muricine in its unguiculate shape, its thickened inner margin, and its centrally depressed, concentrically lined center.
Radwin & D'Attilio, 1976. Original description.

This species resembles A. producta to some degree but differs from it in its more flattened shell, its more gradually tapering spire, its lack of strongly cancellate intritacalx microsculpture, and its lack of spiral rows of pustules on the shell. A. platylaevis also resembles, somewhat, A. pollux and A. castor from the New World; it differs from these in its less rounded aperture, its adherent columellar lip, its much less prominent minor varices, its blunter angles at the periphery, and its finer axial intritacalx sculpture, in addition to substantial radular differences.