Shell small, widely fusiform (SH 4.5-6.25 mm; w/h 0.48-0.50 mm) with well-defined moderately long siphon. Teleoconch of 5 strongly convex to globose whorls. Suture distinct, slightly impressed; subsutural region with 2-3 indistinct wavy spiral lines. Axial sculpture of strong rounded folds (9-10 per whorl). Axial folds intersected by distinct rounded evenly interspaced slightly undulating spiral cords; interstices rather shallow. Spire whorls sculptured by 4 spiral cords, with the third situated on whorls periphery. Last adult whorl with 7 major spiral cords, interstice between 3rd and 4th rather wide with intermediate minor cordlet. Two lower cords on last adult whorl situated on shell base slightly gemmate.
Siphon slightly bent backward, shallowly notched. Fasciole well pronounced, slightly convex, with 5 oblique cords. Aperture elongate; siphonal canal rather broad and shallow. Outer lip strongly convex, bent inward, rapidly constricted to siphon, the inner side with 3 strong denticles. Inner lip slightly convex with labral callus and 2-3 indistinct plicae. Anal sinus rounded, rather wide and shallow.
Colour pattern striped - early teleoconch whorls and subsutural regions of latter whorls brown, their peripheries cream to tan. Base with brown band, siphon cream to tan. Third spiral cord on whorl periphery much lighter than others, white or whitish.
Protoconch cyrtoconoid, brown, of c. 2.7 evenly convex whorls. First 1.5 whorls finely granulated; later protoconch whorls with diagonally cancellate sculpture. Last whorl of protoconch deeply adapically notched at transition to teleoconch.
Radula: description of radula morphology given in the end of the Results section.

The species can be easily distinguished from the rest of the Kermia-Pseudodaphnella complex by its more globose whorls, rather wide aperture and very strong denticles on the inside of the outer lip. T. tridentata nov. sp. is extremely similar to the type species of the genus Thetidos, T morsura described by Hedley (1899) from Funafuti (Tuvalu), and later mistakenly assigned to Lienardia Jousseaume, 1884 (Hedley, 1922). The two species are nearly indistinguishable from each other in teleoconch morphology, but differ in structure of the protoconch, in Thetidos morsura it is 'two whorled, spirally grooved' (Hedley, 1899: p. 473, fig. 42). Specimens of at least two other very similar and most likely, closely related species, were collected in the East Pacific. One of them, undescribed to date, co-occurs with T. tridentata nov. sp. in Vanuatu, and appears to be more common there; the other, from New Caledonia, was originally described as Glyphostoma globulosum Hervier, 1897. Both these species, however, differ markedly from T tridentata nov. sp. The species from Vanuatu has a rather biconical shell with less convex whorls, a protoconch with at least 0.5 protoconch whorls fewer than in T tridentata nov. sp. and the outer lip of the aperture with at least five subequal denticles. Glyphostoma globulosum, which we re-assign to the genus Thetidos, has fewer spiral elements on the last adult whorl, a much deeper anal sinus, constricted at its opening, a straight siphon and a higher protoconch. In addition, the early teleoconch whorls in T tridentata nov. sp. are darker than the rest of the shell, while in Thetidos globulosus these are white.

TYPE MATERIAL. Holotype: MNHN-25603, molecular voucher IM-2007-42400, 6.1 mm, Balicasag Is., Philippines, Expedition Panglao 2004. DISTRIBUTION. Central Philippines and Vanuatu, depth range, living at 20-120 m.