Description. Shell size variable from medium to large, length up to 434 mm, ventricose, globose or sometimes ovate, thick. Protoconch position usually below or occasionally above shoulder of last whorl, but still below top of outer lip. Teleoconch of 2,25 -2,75 % whorls, shoulder ornamented with a row of rather short spines, early growth of spines from quarter to half of first whorl, termination of spines in adult shells is at outer lip or until last quarter of whorl. Spines short and rather broad at base, curved towards protoconch, closely spaced, 12-18 per whorl, length 3-13 mm. Protoconch dome-shaped, of 2 1/2-3 1/2 whorls, whitish or pale yellow or light brown, finely spirally sculptured, with rather coarse radial striae under suture, diameter 10.8-13.3 mm, height 6.0-7.5 mm. Radial growth striae rather coarse, crossed with fine spiral striae. Colour light brown or chestnut with two spiral brown bands, occasionally with two spiral bands of dark brown spots. Aperture wide, semi¬circular, posterior outer lip extends upwards. Interior light cream, columella and approaching lip edge orange. Parietal wall and inside aperture glossy. Columella arched, with three or four oblique plaits, fourth weakest. Siphonal canal notch wide and deep, fasciole well defined. Periostracum thin, brown.

The shell of M. aethiopicus differs from that of other species in its globose shape, the relatively high number and density of its spines (12-18 per whorl), and their short length (up to 13 mm). Occasionally, and from various locations, specimens of M. aethiopicus have been found with top of the lip extending both posteriorly through the protoconch and spines, and laterally across the axis of the shell (Fig. 3B; Dharma, 2005, pl. 52, fig. 6; Morrison & Wells, 2005, figs 2c, 3c). Several specimens of M. aethiopicus from the Kai Islands, Maluku have a striking red internal aperture. A native diver who has observed M. aethiopicus in situ reports that animals having shells with a red internal aperture are found on coral substrates, but not in those that live on sand. Some specimens from the Tanimbar Islands with two spiral bands of dark brown spots have been found. Occasionally, freak spineless shells of M aethiopicus have been found .

Distribution. The western edge of the range of M. aethiopicus is at the Barrang Lompo Islands, Makassar, South Sulawesi. It is also found on several islands in the Banggai Islands, Central Sulawesi. In Maluku, specimens have been obtained from the south of Halmahera Island, Obi Island, Bacan Island, Tanimbar Islands, and Kai Islands, and in Papua it comes from Sorong. Its distribution outside Indonesia follows Hinton (1975), Poppe & Goto (1992) and Morrison & Wells (2005) (Fig. 6).
Habitat. Lives in the muddy sand of shallow seas to a depth of 80 m. Obtained from diving to a depth of 45 m and deep-sea trawling.