Shell large for genus, up to 31.5 mm, solid, elongated, with a tall spire, conical, protoconch rounded, aperture narrow. Protoconch (Figures 11-12) with two smooth, glassy whorls, large, maximum diameter nearly 2 mm, indicating plankto-trophic larval development. Transition to teleoconch distinct, marked by numerous weak axial incremental processes. Protoconch forms smooth keel prior to transition to teleoconch. Teleoconch with up to five roundly convex whorls. Suture constricted, narrow, deep. First teleoconch whorl with four weak initial spiral cords, becoming five on second whorl, eight on penultimate whorl and ca. 30 on body whorl, occasionally with intercalated spiral threads. Axial sculpture of regularly spaced, sinuate, opisthocline ribs, 17 on first teleoconch whorl, 22 on second whorl, forming sharp nodules and cancellated appearance at intersections with spiral cords. Axial ribs and nodules becoming weak and smoother toward penultimate and body whorl. Incremental lines distinct, dense, forming conspicuous axial ridges between spiral interspaces. Varices up to seven in number, very weak on spire whorls, distinct on body whorl. Aperture narrowly elongate, elliptical, deflected from coiling axis by 18° (in holotype). Outer lip thickened, with about 20 obsolete denticles along entire length of the flaring, strongly sinuate outer lip; columellar lip with two developed folds. Radula and soft parts unknown.

Based on its elongate shell with a smooth protoconch and a flaring, sinuate outer lip, we assign this new cancellariid species to genus Mericella. Mericella zhangsupingae new species is most similar to Mericella bozzettii Petit and Harasewych, 1993 (Figures 13-15) in shell size and proportion, but differs in having a larger, lower, more globose protoconch, more convex teleoconch whorls, much weaker axial sculpture, and
more sinuous outer lip. In addition, spiral sculpture is dominant in Mericella zhangsupingae, whereas the axial sculpture is dominant in Mericella bozzettii. Mericella zhangsupingae new species can be clearly distinguished from the other two congeners, Mericella jucunda (Thiele, 1925) and Mericella paschalis (Thiele, 1925), by its larger, thicker shell with roundly convex teleoconch whorls, and a white color. Previously, all members of genus Mericella were only known from off East Africa (see Figure 1). The finding of Mericella zhangsupingae new species extends the distribution of the genus to the western Pacific Ocean.

Type Locality: Off Dongsha Islands, South China Sea, 500-600 m.