Shell large for the genus, up to 20.7 mm in height at maturity (holotype), although one incomplete paratype (MNHN) would have been larger. Height/width ratio 1.73 (holotype). Slender, narrowly ovate with expanded shoulder, lightly built. Subsutural ramp broad, almost horizontal, weakly convex. Tan or light brown, subsutural ramp darker. Abapertural side of apertural flange and ventral part of siphonal canal beige or light tan. Three or four axial, narrow, brown bands on partition. Aperture white. Spire high with paucispiral, weakly shouldered protoconch (observed in one specimen but partly broken). Teleoconch up to five angulate, strongly shouldered whorls. Abapical part of whorls constricted. Suture impressed. Axial sculpture of teleoconch whorls consisting of four, low, thin, sharp lamellate varices, each with a weakly open, inward curved shoulder spine. Apertural varix thin, broad, constricted medially, broader at abapical extremity, extending from shoulder spine almost to tip of siphonal canal. Apertural shoulder spine adapically bent, long, narrowly triangular, straight, connected to last teleoconch whorl by a broad, thin, lamellate partition. Partition with two or three backward bent, short, flattened, broad spinelets. Spiral sculpture very faint, consisting of P1 with the anal tube, P2 (shoulder), P3, P4 and P5 only discernable on variceal flange and only very weakly between axial varices, corresponding to the broad, weakly curved abapertural spinelets at outer apertural margin. P1 with long, rounded, ventrally sealed anal tube, forming an angle of approximately 85-90° with axis of shell. Only apertural tube hollow and functional, older tubes broken off and closed. Two narrow spiral cords between abapical part of aperture and variceal flange, occasionally obvious in some shells. Other sculpture of few, weak and very thin, low, broad scales, only visible on last teleoconch whorl, between axial varices.
Aperture small, rounded, erect, forming a continuous peristome. Columellar lip narrow, outer lip smooth within. Siphonal canal long, broad, straight, ventrally sealed, dorsally bent at tip. Left side of canal weakly overlapping right side.
Operculum and radula unknown.

Typhinellus constrictus differs from all the other Typhinellus species in having a broad, almost straight shoulder ramp, deeply constricted teleoconch whorls with an impressed suture and a rounded aperture.

TYPE LOCALITY. — Madagascar, sector of Fort-Dauphin, 25°15-0'S, 47°14.5'E, 97-98 m. [ATIMO VATAE: stn BS09].
DISTRIBUTION. — South Madagascar, taken alive at 13-20 m, empty shells at 21-102 m.