Turrancilla sibuetae

Turrancilla sibuetae (Kantor & Bouchet, 1999) (Figs 6G–I, 20C–D) Amalda sibuetae Kantor & Bouchet 1999: 11–14, figs 1–2. Turrancilla sibuetae – Kantor et al. 2017: 535. Type material. Holotype MNHN-IM-2000-1459, SL 12.9 mm, and paratype MNHN, SL 10.3 mm. Type locality. Off Mauritania, 20°30'N, 18°34'W, 1855 m, R/V Atalante, EUMELI 2, stn CP05, 06 February 1991. Description. Shell of small size for the genus (up to 13 mm), ovate. Protoconch low dome shaped, smooth, glossy, white, of about one whorl with distinct impressed suture, further suture overlaid by callus. Spire low, conical; primary callus medium thick and covering all whorls except protoconch, slightly impressed at sutures; surface of callus glossy, microshagreened; secondary callus medium thick, extending to right-ventral side of last whorl and continuing up as fairly thin, tongue-shaped pad, reaching suture of antepenultimate whorl. Surface of secondary callus very similar to that of primary one, borders indistinct. Body whorl cloak glossy, covered by very weak and indistinct thin spiral striation. Olivoid groove from very shallow and indistinct to rather distinct. Rear edge of anterior band distinct, in a shape of low but sharp step. Anterior band is of same colour as cloak, microshagreened, not separated into upper and lower parts. Plication plate well separated by broad and deep groove, with poorly pronounced 3 rounded spiral ridges (paratype) or lacking ridges completely (holotype). Columella smooth.Aperture oval, rounded posteriorly; outer lip sharp, in side view slightly opisthocline, with slight, angulation, not corresponding to olivoid groove; siphonal notch moderately deep, asymmetrical. Colour white with slightly yellowish sutural band, overlaid by secondary callus. Operculum spanning 2/3 of aperture (but partly worn), subtriangular, very thin and transparent, yellow, nucleus corroded, but probably terminal (Kantor & Bouchet 1999: fig. 2C). Distinct, narrow, longitudinal, slightly curved rib on its inner surface. Columellar muscle attachment zone long, ovate. Radula (Fig. 20C–D) studied in holotype, typical for the genus, of only about 35 transverse rows of teeth. Radula about 0.6 mm in length (8.9% of AL), membrane about 150 µm in width (2.2% of AL). Remarks. This species is known from two specimens only, reaching 12.9 mm in SL. It is the only representative of the genus in the Atlantic Ocean known so far. Judging from the small size of the penis in the holotype, it may not be fully mature.