TYPE MATERIAL Holotype (MNHN-IM-2000-34855) dim. 2.08 0.77 mm. Protoconch 0.37 x 0.22 mm. stn GB13.
TYPE LOCALITY Caribbean: Guadeloupe, Les 3 arches (Port-Louis), 10 m.
DISTRIBUTION Guadeloupe. MATERIAL EXAMINED Station of Guadeloupe: stn GB13, Les 3 arches (Port-Louis), 10 m, spm 1.
DESCRIPTION Shell small, conical inflated with impressed sutures. Protoconch cylindrical of about 4.5 convex whorls; seen under ESEM minute grains are visible along the sutures. Color yellowish, transparent. Teleoconch of 5 whorls with reticulate sculpture of 3 almost equal spiral cord (1 and 2nd cords closer in first whorls) crossed by weaker axial ribs, about 20 on last whorl; beads at each intersection. A fourth cord is emerging at the base of the last whorl from the in- sertion of the outer lip; border between columella and base highlighted by a weaker cord. Columella short and broad, obliquely truncated, with a surface crossed by thin crisp threads, columellar callus bordering a subcircular aperture; anal sulcus and siphonal canal well defined. Shell semitransparent, pale brown in color with 1 spiral cord darker, beads paler.
COMPARISON Cerithiopsis oliviergrosi n. sp. can easily be confused with Cerithiopsis altiusae n. sp. due to its similar shape and color. The main difference can be found in the protoconch which is cylindrical with grains in the sutures in C. oliviergrosi n. sp. while it is conical with smooth and convex whorls in C. altiusae n. sp. REMARKS The protoconch has characteristics corresponding to the genus Nanopsis Cecalupo & Robba, 2010, a preoccupied name which has recently been amended to Costulopsis (Cecalupo & Robba 2019).
ETYMOLOGY Named after Olivier Gros, Professor at the Université des Antilles, a partner in and facilitator of the KARUBENTHOS expedition.