Iotyrris musivum: DESCRIPTION (HOLOTYPE). Shell height 12.6 mm, shell diameter 4.3 mm, last whorl height 6.6 mm, aperture height 3.9 mm. Shell conical, consisting of 5.75 teleoconch whorls, with high spire, shell diameter to shell height 0.34, aperture height to shell height 0.31, spire height to shell height 0.48. Protoconch brown, consists of 4.25 convex whorls, sculptured with closely spaced axial threads, which are slightly prosocline on most whorls, but turned to strongly opisthocline on the posteriormost part of the last protoconch whorl. There are around 25 threads on the last protoconch whorl. Teleoconch whorls nearly flat, slightly angulated at the shoulder. Last whorl sharply narrowing towards attenuated, nearly straight siphonal canal. Suture shallowly impressed, slightly wavy. Subsutural ramp narrow, with single strong sharp keel, followed by narrow thread. Immediately below the ramp, two narrow, closely spaced cords that are tall and triangular in section form the shoulder. Below there are four broadly spaced subequal cords, separated by smooth interspaces. There are 5 thinner and more closely spaced cords on the shell base and 8 narrower and closer-spaced threads on the canal. Axial sculpture absent, except for inconspicuous growth lines. Aperture narrowly oval. Outer lip thin, evenly rounded. Anal sinus deep, situated on the shoulder. Inner lip slightly convex, columellar part straight, callus very narrow, not extending onto the parietal wall. Color creamy white, with regularly spaced, light brown spots covering cords of the entire shell surface and much more pronounced, strong, darker subrectangular spots on the shoulder cords. Operculum yellow, transparent, leaf-shaped, with terminal nucleus.

Iotyrris musivum: New Caledonia, Loyalty Islands, Vanuatu, shallow water, intertidal to 16 m.