Description Shell small, fusiform (W/H 0.42, A/H 0.5), spire with somewhat rough, corrugated appearance. Protoconch missing; teleoconch of ca slightly over 5 whorls, suture adpressed. Early teleoconch whorls subcylindrical, with well-developed subsutural band, separated from lower portion of whorl by deep groove; periphery of whorl flattened. Axial sculpture of orthocline, rather densely set ribs, well- developed on spire including on penultimate whorl, but vanishing completely on last whorl. Penultimate whorl with 19 ribs. Spiral sculpture below subsutural band consisting of cords (three on periphery of antepenultimate and penultimate whorl), stronger developed in interspaces between ribs. Intervals between cords of about equal width, forming deep pits in interspaces between axials. Last whorl with gently convex profile above insertion of outer lip, marking transition to rather short and quickly narrowing shell base, gradually extending to siphonal canal. Sculpture of strong, elevated, subequal cords, counting 11 from upper suture to siphonal canal. Canal rather short, tapering, with five weaker cords, becoming progressively more oblique. Aperture elongate, lacking both siphonal notch, and apical callous pad; outer lip evenly convex along its entire length, with 6 widely set lirae inside. Inner lip with well-developed white callus; columella with 5 fine, nearly subequal folds. Shell surface mated, thin periostracum, microsculpture of densely set growth lines, pronounced on last whorl, color light brown; inside of aperture white. Radula of about 55 rows of teeth. Rachidian with rather short and broad base, and three broadly interspaced pointed cusps. Shallow pits at cusps base, corresponding to tips of the following rachidian cusps, thus facilitating interlocking of radular teeth in adjacent rows. Laterals sickle-shaped with one long cusp. Etymology The species epithet refers to the strong elevated cords of the new species with somewhat rough appearance when uncleaned, a sculpture resembling that in species of the North Pacific buccinid genus Ancistrolepis. Noun in apposition. Distribution West Pacific: Philippines, Papua New Guinea, Vanuatu, New Caledonia. Remarks Costapex ancistrolepis sp. nov. is very similar to C. sulcatus, and C. dolichosulcatus. While C. ancistrolepis seems to differ in having a more ovate shell compared to C. sulcatus (which has a more biconical shell with a longer aperture), the examined material is too scarce to draw definite boundaries, and accurate identification of the species would require DNA data. For comparison between Costapex ancistrolepis sp. nov. and C. dolichosulcatus sp. nov. see the Remarks section under corresponding species. Finally, C. ancistrolepis sp. nov. can be differentiated from another somewhat similar species, C. margaritatus Hermann, Fedosov & Bouchet, 2017 . by having a more distinct subsutural band, straight siphonal canal, and the number of columella folds (five vs four in C. margaritatus). Costapex ronnyi is easily distinguishable from Costapex ancistrolepis sp. nov. and other Costapex species by the prevalence of axial sculpture, and the uniform reddish-brown shell color.