Shell small (adult?), up to 9.50 mm long, weakly arched (length/height ratio 3.30-3.55), apex weakl inclined anteriorly. Anterior end occupying 3.20-3.55% of shell length; slopes weakly convex, almost flat. Aperture gentl arched from side to side, no indication of twisting with increasing size. Teleoconch I conical, length 2.30-2.40 mm, anterior slope weakly concave, lateral and posterior slopes more or less flat, glossy, essentially smooth apart from commarginal growth lines and obscure radial lines. Teleoconch II sculptured with strong radial costae and commargin ridges, small rounded nodules at intersections; fine, crisp, crowded commarginal growth lines throughout. Radial costae rounded, multiplying by intercalation, most interspaces narrower than each costa. Radular teeth (holotype MNHN IM-2009-10788) roughly 170 mu long, with 11 cusps, posterior pair fused. Holotype length 9.50 mm.

In its depressed-conical shape at the same stage of growth, P. philippinarum n. sp. resembles P. beta n. sp., P. orientalis Schepman, 1908 and P. gamma n. sp., differing from R beta n. sp. in having a larger P1 (length 2.30-2.40 vs. 1.90-2.20 mm) and narrower radial costae, from R orientalis in having a more narrowly oval P1 and much more closely paced commarginal ridges, and from R gamma n. sp. as well as R obtusa (Thiele, 1925) in that PI is not twisted relative to the longitudinal axis of PII.

Philippines.