Shell rather small for genus, adult size up to 9.2 mm; fusiform, elongate, very slender. Suture slightly impressed. Protoconch paucispiral, 1.75 whorls. Teleoconch of 6-6.5 whorls. Axial sculpture of fine growth lines only. Spiral sculpture of basal cords, ventrally ranging to just above adapical edge of columella, weakening adapically. Outer lip S-shaped, not thickened, smooth, bearing only continuation of basal cords. Inner lip smooth. Columellar callus very weak. Parietal callus very weak, almost obsolete. Columella smooth. Siphonal canal short, open, slightly recurved. Teleoconch whorls ofF-white in colour with much clearer white band just above mid-whorl on later whorls, appearing as semitranslucent band just below suture on first whorls. Protoconch ofF-white with semi-translucent, brownish subsutural band. Aperture and columella white to off-white. Operculum typical of genus; pale brown, semi-translucent, with terminal nucleus. Holotype height 9.2 mm.

Mitrella praetermissa is very similar to Mitretla longissima K. Monsecour & D. Monsecour, 2007, a species found in more shallow water (18-60 m). Both are of roughly the same size and general shell form, but Mitrella praetermissa can be distinguished from Mitrella longissima by its more elegant protoconch (both are paucispiral), more elegant shell shape, the S-shaped aperture, the presence of the brown subsutural band on the protoconch and the white band just above mid-whorl.

Known only from Norfolk Ridge, alive in 200-212 m.