Shell up to 35 mm in length at maturity, spinose. Spire high with 1,5-1,75 protoconch whorls and up to 6 or 7 lightly shouldered teleoconch whorls. Protoconch whorls rounded, smooth, glossy. No apparent terminal varix. Suture weakly impressed or appressed. First teleoconch whorl with 9 or 10 axial ribs, second with 7 ribs, third to last teleoconch whorls with 3 varices. No other axial sculpture except occasionally one low (rarely strong) intervaricial node and some growth striae. Varices of last whorl with 3 ventrally sealed, sharp or blunt, more or less adapically bent spines, sometimes joined with a varicial webbed expansion. Spiral sculpture consisting of conspicuous, mostly weak, numerous smooth or scabrous threads; occasionally with low cords that interconnect the varicial spines. Shell surface smooth, or covered with vaulted scales. Aperture roundly-ovate. Columellar lip smooth, rim weakly erect, adherent at adapical extremity. Anal notch obsolete. Outer lip smooth, weakly erect. Siphonal canal short or medium-sized, straight, sealed, with 2 or very rarely 3 sealed, short, acute spines. Colour light to dark brown. The study of more than 250 specimens from various localities was a great help in determining the high degree of variability in that polymorphic species. The shape, length and position of spines, as well as the spiral or/and axial sculpture may be different from one specimen to another. The length of the shell depends naturally on the number of teleoconch whorls.

The shell reaches a maximum length of 30 mm and is fusiform. The spire is high and acute, consisting of four strongly shouldered postnuclear whorls and a protoconch of undetermined nature. The suture is weakly impressed. The body whorl is moderately large and fusoid. The aperture is ovate and moderately small, with an obsolete anal sulcus. The outer apertural lip is weakly erect and smooth, its inner surface also smooth. The columellar lip is smooth and erect. The siphonal canal is moderate in length and its margins are fused. The body whorl bears three briefly spinose varices. Intervarical axial sculpture consists of a single knob, closer to the older of any two consecutive varices. Spiral sculpture is lacking on the 1 shoulder. The body bears three obsolete cords, one at the shoulder margin and two below it. Two other cords are found on the canal. Where these cords intersect the varices, comparatively short, sharp, posteriorly hooked, ventrally fused spines are developed. The spine at the shoulder margin is much the longest; the remainder are shorter and become progressively shorter anteriorly. The entire shell surface is covered with a microsculpture imparting the appearance of oblique chisel punctures. Shell color is pale rusty orange; the aperture is white.

The holotype of P. uncinaria has strongly adapically bent shoulder spines, only occasionally seen in that species , but otherwise typical of P. graagae (Coen, 1947), another South African species from which P. uncinaria differs in having fewer, regularly longer and broader varicial spines, a somewhat shallower suture, and more rounded whorls. This peculiar spine ornamentation in the holotype of P. uncinaria has led to some misidentifications, and the erroneous synonymisation of P. graagae with P. uncinaria. Mienis (1979) already noted these misidentifications and reinstated Coens taxon.

South Africa: From Port Alfred to North of Cape Town. Namibia: Bakers Bay and Hottentots Bay.