Shell: Medium size for genus (H up to 6.0 mm, W up to 10.6 mm), wider than high, conical to slightly coeloconoidal in shape, glossy; spire moderately depressed, height 0.51x to 0.60x width, about 1.70x to 1.92x aperture height; periphery weakly subangulate; umbilicus broad and deep. Protoconch about 350 um wide, 1.25 whorls, rounded, with 3 thin, evenly spaced, spiral cords and with a straight, slightly expanded terminal lip without varix. Teleoconch up to 4.5 convex whorls with a weak subsutural ramp on first whorls, vanishing on last whorls; early whorls with 5 smooth spiral cords, rapidly ceasing; subsutural axial pleats on intermediate whorls; last whorls smooth with poorly visible spiral threads near periphery. Suture canaliculated on first whorls, impressed on last whorls. First whorl convex, sculptured with 4 smooth spiral cords appearing immediately after protoconch and P1 half a whorl later; P2 strongest, at edge of subangulate subsutural ramp. On second whorl, SI and S2; P2 much wider but flattening; axial threads becoming quickly flat axial pleats; subsutural ramp weakening; narrow translucent subsutural spiral band appearing at end of whorl. S3 appearing on third whorl; all cords ceasing except S3 and P4; subsutural axial pleats stronger and subsutural ramp vanishing. Last whorls smooth, S3 and P4 as faint spiral cords still poorly visible at periphery. Aperture rounded triangular; peristome incomplete; outer and inner lip thin; inner lip with a weak thickening against umbilical rim. Base convex; weak smooth axial pleats variable: sometimes occurring in inner part of umbilicus, opposite aperture or without distinct pleats on last half, or all around umbilicus or rarely nearly absent; thin spiral cord bordering umbilical rim. Umbilicus broad (diameter 30-32% of shell width), central, with perspective to apex, with angulate rim, with vertical wall, 8 to 10 smooth thin spiral cords inside, sometimes closer to each other in adapical part, and usually without axial threads (rarely very thin and very weak close axial threads on umbilical wall); axial pleats on umbilical shell walls of adapical whorls. Colour: Teleoconch nacreous white with irregular brownish flames, forming usually a band patterned with subsutural chevrons and often another peripheral band of regular maculations; protoconch off-white.
Operculum: Corneous, multispiral with central nucleus, light brown.
New Caledonian I. stephanophora specimens (n = 52 adults) have two striking features: a high vari¬ability regarding the axial pleats around the umbilicus (all around, only on some parts, or even in rare cases, almost absent) and a wide New Caledonian distribution, over a wide range of habitats and depths. The Fijian specimens (n = 17 adults), for which molecular data are lacking, are more constant regarding their conchological features, always having axial pleats all around the umbilicus and 10 spiral cords inside.
The new species weakly resembles I. fulgens from Japan, Taiwan and Philippines, and I. polygramma from Indonesia but these species with a more or less similar size have only 4 primary cords. Moreover, I. fulgens has a more rounded shape and thin axial threads on the whole surface of the whorls while I. polygramma is more depressed.

New Caledonia, 82-580 m, lv at 82-250 m; Loyalty Islands, 250-350 m; Fiji, 173-313 m; Futuna Island, 260-300 m.