Shell large. 84.2 mm, elongate-subcylindrical. thin but rather solid, with a tall spire and a long narrow bod)-whorl, gradually tapered to a short unnotched spout-like anterior canal. Base weakly convex, smoothly merging with canal. Teleoconch with about 10 whorls, first 6-7 whorls angulated below middle, then weakly convex, subsutural ramp poorly differentiated. Aperture narrowly oval. Labrum thin, evenly curved without stromboid notch. Canal short, broad, open. Columella thin, indistinct. Anal sinus moderately shallow. Axial sculpture consisting of short, orthocline axial ribs starting just above angulation and forming knobs at periphery, strong on first whorls, weaken on the last 2-4 whorls. Rough growth lines in between axial ribs, thickened on subsutural ramp, also becoming much weaker on last whorls. Spiral cords low, broad, flattened, with very narrow interspaces, absent in subsutural ramp. On last whorl spiral cords becoming gradually narrower (and the interspaces broader), stronger and rounder towards the siphonal canal. Shell colour dull whitish to pale beige; interior of aperture and columella porcellanous white. Protoconch missing. No soft parts were available for study.
Shell size up to 103.0 mm in length, b/l 0.29 ± 0.02, a/l 0.50 ± 0.02 (mean and standard deviation are given, based on the eight type specimens).

Spergo parunculis differs from S. fusiformis (Kuroda & Habe, 1961) (type locality: Japan, Tosa Bay, 300 m; figs. 1-9) by having strong and broad spiral cords persisting at the teleoconch whorls whereas they become obsolete or at least very shallow and fine in the late whorls of typical S. fusiformis specimens. Moreover, S. parunculis n. sp. has less convex whorls and a more slender shell; the ratio between shell breath and shell length is lower (0.29 ± 0.02 (measurements based on the eight type specimens) compared to 0.35 ± 0.02 for S. fusiformis (measurements based on three specimens from Japan and East China Sea).
Spergo parunculis n. sp. differs from & glandiniformis (Dall, 1895) (type locality: Hawaii, off Honululu, 298-375 fm), and S. aithorrhis Sysoev & Bouchet, 2001 (type locality: South of New Caledonia, Norfolk Ridge, 600 m) also in the broad spiral sculpture and, additionally, in having a larger and more slender shell with a higher spire, and less convex whorls.

So far known only from the eastern part of the Mozambique Channel (from Majunga tc Tulear), between 400 and 800 m.