Type material. Holotype: 8.8 km south of San Benito Islands, Baja California (28° 13.2'N, 115° 33.4' W), R/ V Velero III 1251-41, 26 February 1941, on coarse and fine sand at 126-144 m holotype LACM 3082 (ex LACM 1941-31.25), length 14.7 mm, width 6.8 mm, 1 lv.
Distribution. Known only from vicinity of San Benito Islands, Baja California, 126—174 m.
Description. Shell extremely small for genus, tall, narrow, elongate, whorls rotund, peripheral cords projecting into spines, shell somewhat thin, length to 14.7 mm, width 6.8 mm (holotype). Protoconch characteristically tabulate, slightly rounded, somewhat loosely coiled, tabulate, subtly rotund at periphery, carination wanting, spire tall, whorls elevated. Teleoconch sculpture of very fine scabrous growth lines overriding thick primary cords, remarkably round, stronger at periphery, projecting at each rib intersection, hollow spines at rib intersections, peripheral spines upturned, anteriorly cords project outward, cord sequences variable, shoulder tabulate but rotund in profile, suture impressed, color off white, semi-transparent between cords on final whorl. First whorl with P1, P2, second whorl with P1, P2, starting s2, third whorl with P1, P2, s2, starting P3, fourth whorl with P1, P2, s2, P3, starting sl, final whorl with P1, sl, P2, s2, P3, s3, P4, (s4), P5, (s5), ADP, ads, MP, ms, ABP. Aperture large, round, slightly ovate, outer lip relatively thickened, with heavy growth scabrations, columellar lip thick, smooth and protruding, slightly wider at base, twisted anteriorly. Denticles decreasing progressively in strength anteriorly with Dl, D2 split, D3, D4, D5. Siphonal canal thin yet robust, width relatively broad, canal extraordinarily long, twice bent. Operculum ovate, thin, pointed at anterior end.
Remarks. Compared to P. neobarharensis . P. benitoensis is much smaller in size, has a more rounded whorl profile, less projecting spines, maintains a more slender shape, primary cords are more upwardly projected and prominent, secondary cords are much more subtle, the whorl profile is more rotund, the suture is more indented, and the shell is overall thinner. Both species inhabit deep waters but P. benitoensis is presumed to be endemic to the San Benito Islands, Baja California.
Etymology. Named after the San Benito Islands, Baja California, where the type specimens were collected.