Diagnosis. A Calliostoma species of rather small size, with a moderately elevated, coeloconoidal spire, up to 8 granular spiral cords (P2, P3; PI, P4; S2, SI; TI, T2), P3 the strongest with blunt sharp beads, a flat base with up to 14 smooth spiral cords, without umbilicus, a yellowish light brown colour with regular brown patches covering two or three beads and separated by two or three white beads on P3.
Shell rather small for the genus (H up to 11.4 mm, W to 11.5 mm), more or less as wide as high, weakly coeloconoidal in shape; spire moderately elevated, height l.Ox to 1.2x width, 3.4x to 3.9x aperture height, apical angle 54° to 56°; angulate periphery; anomphalous.
Protoconch about 200 µm wide, 1.25 whorls, rounded, with a straight terminal varix.
Teleoconch up to 7.3 weakly convex to almost flat whorls; early whorls with 3 spiral cords, last whorl with 8 cords.
Suture weakly impressed, not canaliculated. First whorl convex, sculptured by about 12 rather thick, axial, prosocline ribs and 3 granular spiral cords, beads produced by intersection of cords with ribs; P2 and P3 appearing almost immediately and simultaneously, PI a quarter of whorl later; P3 quickly slightly stronger than other cords with thick, blunt sharp beads; distance between ribs similar in size to width of ribs, distance between P2 and P3 about 1.5x distance between PI and P2. Second whorl only weakly convex, beads of cords stronger, P3 with much stronger beads than other cords, making a suprasutural depression into profile of whorl; P4 almost completely hidden by next whorl. Third whorl more or less flat; S2 appearing, quickly as strong as P2; P4 a bit more visible. On fourth whorl, P3 still much thicker than other cords and PI stronger than P2 and S2, with rounded beads; axial ribs vanishing, except between S2 and P3; SI appearing, thin. On fifth whorl, TI appearing between P2 and S2, then T2 between S2 and P3; S3 absent. On last whorl, P4 peripheral, thin; angulate periphery; beads of all spiral cords rounded, slightly vertically elongated except those of T2 and P3 blunt sharp; distance between cords slightly smaller than cords.
Aperture subquadrate. Columella straight, slightly oblique.
Base almost flat, with about 14 smooth spiral cords; distance between cords similar to cords. Colour of teleoconch yellowish light brown, with possible slightly darker, irregular axial flames; regular brown patches covering two or three beads and separated by two or three white beads on P3 on the last whorls, also on PI and P2 on two early whorls; base yellowish light brown; protoconch whitish.

Calliostoma pilidion n. sp. can be compared to Fautor chesterfieldensis (B.A. Marshall, 1995) from Chesterfield Islands (Figs 5I^M, 8G-H), but this more or less similar in size species has a strictly conical shape, a greater H/W ratio (1.50— 1.69x), a larger protoconch (430-450 µm), a larger apical angle (60-64°), a P3 not very different of the other cords and a different ontogeny of cords with S3 present (P2-P4; PI; S3, S2 ; SI; Ti). The new species is a bit comparable to C. xanthos B.A. Marshall, 1995 from New Caledonia, but this larger species has a different ontogeny of cords with S3 present (P2, P3, P4; PI; S3, S2; SI) and with strong S3 and P4 similar in size and very close. The new species seems superficially close to C. xylocinnamomum Vilvens, 2005 from Fiji but this similar in size species has a different ontogeny of spiral cords (P2, P4; PI; P3; S4; S2, SI; S3; Ti) with a not so strong peripheral cord, a larger protoconch (450 µm) and a base with about 10 strong granular cords.

Type material. Holotype (11.4 x 11.5 mm) MNHN-IM-2000-38733. Paratypes: 2 MNHN (MNHN-IM-2000-38734, MNHN-IM-2000-38735- as listed below).
Type locality. West of New Caledonia, north-west of Bellona plateau, EBISCO, stn DW2564, 0°25'S, 158°41’E, 333-386 m.
Material examined. West of New Caledonia.
EBISCO: stn DW2564, 20°25'S, 158°41'E, 333-386 m, 1 dd (holotype), 1 sub dd (paratype MNHN-IM-2000-38734 ). KANADEEP 1: stn DW4977, 19°46'S, 158°30'E, 280-304 m, 1 dd (paratype MNHN-IM-2000-38735).
Distribution. West of New Caledonia, 304—333 m (dead).