TYPE MATERIAL Holotype (MNHN-IM-2000-34862) dim. 3.20 × 1.06 mm. Protoconch 0.52 × 0.44 mm. stn AD267.
TYPE LOCALITY Caribbean: Martinique, Macouba, au large, 77 m.
DISTRIBUTION Martinique. MATERIAL EXAMINED Station of Martinique: stn AD267, Macouba, au large, 77 m, spm 1.
DESCRIPTION Shell medium in size, conical with slightly constricted last whorl, sutures not very discernible, background color opaque orange, beads paler. Proto- conch cylindrical of 2.5 whorls, apex very small, subsequent whorls show 2 spiral cords of beads, in the 2nd cord the beads are bigger, more prominent and slightly opisthocline. Teleoconch of 6.5 whorls with reticulate sculpture of 2 spiral cords (2nd narrower) crossed by weaker axial ribs, 14 on last whorl; beads at each intersection, rectangular on 1st cord, interspace between spiral cord wider than sutures. A fourth cord is emerging at the base of the last whorl from the insertion of the outer lip; border between columella and base highlighted by a thick cord. Columella very short, obliquely truncated, columellar callus bordering an oval aperture; anal sulcus and siphonal canal well defined.
COMPARISON We do not know any similar shells; protoconchs with a similar sculpture are typical for the genus Mendax Finlay, 1926.
ETYMOLOGY Named after Thomas Rostaing, Head of the Maritime Activities Development Unit at the Direction de la Mer in Martinique, for his understanding and support of the MADIBENTHOS expedition.