Type locality: Philippines, Bohol/Sulu seas, 08°39'N, 123°16'E, 255-301 m, PANGLAO 2005, st. CP2372.
Description (holotype). Shell thin, fusiform, with high spire and long narrow straight siphonal canal. Protoconch paucispiral, globose, of nearly two smooth strongly convex smooth whorls, slightly eroded in holotype. Protoconch/teleoconch transition is eroded and not discernible. Protoconch diameter around 1.1 mm, height around 1 mm. Teleoconch whorls strongly angulated at periphery, slightly over 6 in total. Suture shallow, subsutural región wide, distinctly concave, having indistinct spiral riblets. Median peripheral keel strong, on upper teleoconch whorls slightly above suture, then progressively albeit slightly shifting upwards. Keel forming distinct broadly spaced nodules (10 on first whorl, 14 on second), penultimate whorl with 16 nodules, last with 15. Upper corners of intact nodules slightly attenuated and raised adapically. Median keel with 2-3 irregularly spaced riblets seen in interspaces between nodules. Below median keel few irregularly spaced and very weak riblets.
Shell base sharply narrowing towards siphonal canal. Aperture oval, constricted posteriorly with broad but very thin parietal callus, outer lip fragile, very weakly concave in upper part, with distinct notch corresponding to median keel and weakly convex below shoulder, gradually passing into canal. Anal sinus judging from growth lines broad, medium-deep, deepest point in center of median keel. Growth lines numerous, thin. Shell yellowish, with contrasting lighter and darker axial lines corresponding to growth lines. Interspaces between nodules light brownish.
Measurements (holotype): SL 17.4 mm, AL (with canal) 9.2 mm, SW 6.4 mm.
Radula of marginal teeth only, very similar to R molengraaffi. Marginal teeth of modifíed dúplex type, major limb pointed, lanceolate, médium broad, with thickened edges and depressed central portion, outer end (tooth base) poorly sclerotized. Accessory limb much narrower, although long and extends on outer edge beyond the limit of major limb. It is divided by deep longitudinal furrow along most of its length in two lobes, inner longer.
Remarks. The new species differs from R mo-lengraaffi in having slightly smaller shell with more abruptly narrowing shell base and weaker spiral threads on shell base. Nevertheless only one specimen of the new species is known and its variability therefore is unstudied. The genetic distance between the two sequenced samples, one of P. philippinensis and one of R molengraaffi, is 11.4%.
Etymology: the species epithet refers to the type locality.
Distribution. Type locality only.