Shell of moderate size, up to 13.87 mm long, strongly arched (length/height ratio 1.66-2.14, mean 1.85, SD 0.13, n = 14), apex weakly inclined anteriorly. Anterior end occupying 20.7-31.9% (mean 26.9%, SD 3.08, n = 14) of shell length; anterior slope weakly concave in shells 11-12 mm long, then weakly convex, lateral slopes weakly convex, posterior slope broadly convex. Aperture gently arched from side to side. With increasing growth, longitudinal axis gradually twisting up to roughly 5° anticlockwise between teleoconch I and end of teleoconch II in adults. Teleoconch I conical, length 1.60-2.10 mm (mean 1.85 mm, SD 0.13, n = 14), anterior and lateral slopes flat or weakly concave, poste¬rior slope mostly weakly convex, more or less flat in few specimens, glossy, essentially smooth apart from commarginal growth lines and obscure radial lines. Teleoconch II sculptured with radial costae and commarginal ridges, rounded nodules at intersections; fine, crisp, crowded commarginal growth lines throughout. Radial costae rounded, multiplying by intercalation, interspaces narrower than each costa. Radular teeth (adult, paratype NMNZ M.306245 ex MNHN IM-2009-9296) roughly 250 (am long, with 16 cusps, posterior pair small and fused, others sharp. Holotype length 12.04 mm.

Pectinodonta alpha n. sp. is distinctive among Pectinodonta species in the combination of moderate-sized, acutely conical shell with strongly anterior apex, and relatively weak commarginal ridges. Compared with P. obtusa (Thiele, 1925) from off Sumatra, 750 m, which has similar sculpture, P alpha n. sp. differs in being more elevated, in having the apex closer to the anterior end, and in that teleoconch I is less skewed from the longitudinal axis.

Solomon Islands and Vanuatu, living at 290-777 m