Holotype, adult shell. Length 25.2 mm. Protoconch of 1.75 whorl, tiny (0.3 mm in width), protruding, shaped as a Phrygian cap, smooth, light mauve. Teleoconch of 9.75 whorls, smooth and shiny, apex acute, spire narrow and slender, weakly stepped, outline of the sides weakly convex, number of spiral furrows from 3 on the upper whorls to 7 on the lower whorl of the spire, the fourth and the fifth furrows below the suture being deeper and wider, the same pattern of spiral sculpture on the last whorl with a total of 23 spiral furrows, including 4 wide and deep furrows at the left of the aperture. Aperture narrow, length about 42% of total length, outer lip profile receding, siphonal canal short, sinuous and faintly twisting, siphonal notch well-marked, no anal notch, columellar border smooth, oblique and weakly sinuous.
Ground colour white, top of the spire mauve, one row of large axial light honey brown marks on the spire whorls, two rows on the last whorl separated by a white spiral gap at mid-whorl, a white spiral band at the top of each whorl, base of the shell white.
Animal, operculum and radula unknown.

In many respects, P. ghanaensis resembles P. nifat (Bruguiere, 1792), which is widely distributed from central Senegal to Angola, and which is rather common off western Ghana, where it was found in the vicinity of P. ghanaensis. P. nifat shows a very constant shell morphology and decoration along its whole range of distribution (FBC and PRC).
P. ghanaensis differs from P. nifat in having a smaller size, a more slender and less inflated outline with less stepped whorls, a mauve apex instead of a honey-brown one, numerous well-marked furrows instead of few faint ones, an attenuated narrow keel pointing at the base instead of a thickened keel with a stepped callus encompassing the base, one spiral row of long squarish light honey-brown marks on the spire whorls and two rows on the last whorl, instead of fragmented smaller dark red brown marks making a checked pattern in P. nifat (STREBEL, 1914). The spiral sculpture of P. ghanaensis matches more closely the pattern found in the group of P. Candida (Philippi, 1848), but it differs in all other respects (STREBEL, 1914; KNUDSEN, 1952).

Type locality: Off Sekondi, western Ghana, 20-30 m. Type material: Holotype MNHN (Fig. 7): 25.2 x 8.9 mm; paratypes 1 to 5 PRC: ad. and juv. spm. (larger spm.: 28.8 mm). All from the type locality.
Distribution: Only known from western Ghana, 18-20 m to 30-35 m. P. ghanaensis sp. nov. can be considered as endemic from western Ghana.