Shell of moderate size for genus, to 38.3 x 15.2 mm. fusiform, slender, with about 9 whorls, prominent axial ribs and spiral cords, and abundant axial lamellae. Protoconch of 2 elevated whorls, first whorl smooth, rounded, tip immersed; second whorl not much wider than first; sides slightly convex, with 3-4 very faint axial riblets near terminus. Teleoconch of 7 whorls, each with 6 or 7 rounded, node-like, seldom aligned axial ribs; whorls 1-4 each with 4 spiral cords; 2 middle cords crossing ribs stronger than others; cord bordering anterior suture increasing in strength toward anterior whorls; whorls 5 and 6 with 5 cords, 3 anterior cords stronger. Body whorl with about 11 cords of various strengths; 3 cords at and anterior to periphery more prominent than others; surface of spire and body whorl with many axially aligned micro-lamellae and (sometimes) with 1-3 fine spiral threads between cords. Suture deeply impressed, undulant in accord with ribs and interspaces; sutural ramp bearing many prominent scale-like lamellae on middle whorls (3-5); lamellae less prominent on anterior whorls; base and siphonal process slender, elongate, with 8-10 oblique cords of various strengths extending to truncate tip. Aperture subovate; outer lip thin, highly arched, slightly crenulate, inner side bearing 9-11 low, straight, sometimes discontinuous lirae; several anteriormost lirae beaded. Columella nearly straight anteriorly, arched posteriorly, with small node-like callous on parietal shield and faint undulations suggestive of folds near callous at anterior end. Siphonal canal slender, straight, smooth within, with lamellate inner edge forming distinct pseudoumbilicus near tip. Shell exterior light orange-brown, with lighter hue extending in vague band across ribs of spire; protoconch and shell interior white. Operculum and radula unknown.

Brown shells of L. lamyi distinguish that species from L. ceramidus and L. eburneus, which have white shells. Spiral cords that cross the ribs of L. lamyi are stronger than those of L. ceramidus but weaker than those of L. eburneus. Sutural lamellae are less densely packed on L. lamyi and L. eburneus than on L. ceramidus but are arrayed over more of the sutural ramp on L. lamyi than on L. eburneus. The larger shell (holotype) of L. lamyi has beaded lirae within the aperture, a feature shared with L. ceramidus but apparently not with some other congeners. The outer lip of the holotype is thin and not fully developed, suggesting that the specimen may be immature and the species may attain somewhat greater size.

Known only from type locality off Martinique, French West Indies, depth 250 m.