Shell large sized for the genus, up to 18.9 mm in length at maturity (holotype). lanceolate, heavy, weakly nodose. Spire very high, with 1.5 protoconch whorls, and up to 6-6.5, broad, convex teleoconch whorls. Suture adpressed. Protoconch small. Whorls rounded, smooth, glossy; ending straight, abrupt. Axial sculpture of teleoconch whorls consisting of high, broad, rounded ribs. First to third whorls with 11 or 12 ribs, fourth with 11, fifth with 9 or 10, last with 8 or 9 ribs, and broad, strong terminal varix, occasionally with 1 or 2 other erratically placed varices. Spiral sculpture of low, broad, primary and secondary cords, and weak threads. Last whorl, including shoulder, with 6 or 7 primary cords, 6 or 7 secondary cords between each pair of primary cords, and usually a thread between secondary and primary cords. Aperture small, ovate. Columellar lip narrow, smooth, with small parietal tooth, adherent, briefly and weakly erect abapically. Anal notch broad. Outer lip weakly erect, crenulate, with 5, occasionally 6 strong, broad denticles within. Abapical denticle strongest; when 6 denticles, adapical (additional) denticle small. Siphonal canal short, weakly dorsally bent, sealed, spirally sculptured. Uniformly white, dirty-white, or tan-white. Aperture white. Operculum pale brown, D-shaped. with lateral nucleus in lower right. Attached surface with about 4 growth lines, and broad callused rim. Radula: not examined.

Ocinebrina leukos differs from O. edwardsi (Payraudeau. 1826). which in La Caleta, Lanzarote, occurs sympatrically with O. leukos, in being larger, and very stable in form, sculpture, and color, while O. edwardsi has a highly variable morphology, even in a single locality, as in La Caleta. O. leukos constantly has a uniformly whitish shell with a very high spire, broad axial ribs, broad, rounded outer apertural lip. and broad, voluminous last teleoconch whorl. I have never observed a single specimen of O. edwardsi from the Canary Islands, or from any other locality, with those combined characters. O. edwardsi may be occasionally (rarely) of a uniform white colour, or may have a broad apertural lip, or a high spire, but then it lacks other characters, peculiar to O. leukos.
0. leukos was recorded, and illustrated by Nordsieck & Talavera (1979: 113. pl. 30, fig. 17) as O. nicolai Monterosato, 1884, a different species known from scattered localities throughout the Mediterranean Sea.

Canary Islands, NW Lanzarote, intertidal.