Shell rounded, rather depressed, somewhat fragile, whitish, with a convex dorsal part and a flat base. Protoconch hyperstrophic, of nearly 2 smooth whorls of about 390 µm diameter. Teleoconch of about 1-1,5 whorls, with only 1 suprasutural cord at the beginning, which forms the peripheral angulation. Three more cords appear in the middle of the first whorl, being more or less granulous; one more appears at the end of the spire in subsutural position. The total dorsal surface is crossed by numerous fine curved prosocline threads; ventrally, slightly concave with some irregular curved oblique threads which change into nodules on the peripheral keel. Two prominent cords run from the umbilicus up to the base of the aperture. The lower one represents the border of the umbilical infundibulum. The axial sculpture is variable, sometimes appearing as ribs and sometimes only growth lines. The aperture is ovoid depressed with the upper part of the outer lip sharp and advanced dorsally. Umbilicus wide and open showing the previous whorls.Dimensions: The holotype is 1.9 mm in diameter. Other shells can reach 3.0 mm. The specific name alludes to the sculpture which is more attenuate in this species than in others of the genus.

Some variability exists in the shells of this species, mainly in the sculpture of the dorsum and the peripheral cord. The shells with the morphology of the holotype have an attenuate sculpture and the peripheral cord undulates. Other shells have a more prominent dorsal sculpture which is also more evident on the peripheral cord. Those spiral cords may be even more numerous being formed by prominent and nodulous spiral cords and by fine prosocline axial ribs. The last whorl has 5 spiral cords at the periphery and 2 on the base. There are strong axial ribs between the basal cords, but there are no axial ribs between the outer basal cord and the peripheral cord. The base is slightly convex. Anyway, we think that this form here commented is an extreme in some characters.
ADAM & KNUDSEN (1969: 43-44, fig. 23) considered the shells with morphology similar to the holotype of this species as an attenuate form of Tornus suhcarinatus. Those figures were reproduced by GIANNUZZI-SAVELLI EX AL. (1997, fig. 553). In our opinion, T subcarinatus is present from Europe south to Senegal, and the shells from this last area have morphology identical to those from the European Atlantic. T. attenuatus occurs also in Senegal with its typical sculpture, and no intergrades between them have been observed. T. subcarinatus has a more solid shell, a more prominent sculpture with very numerous axial ribs, which do not appear in T attenuatus. At the base, the ribs of T subcarinatus are more numerous, while in T attenuatus the ribs are low in number and less evident. Furthermore, the axial sculpture of T subcarinatus is orthocline or slightly opisthocline, while that of T attenuatus is prosocline. Finally, the protoconch of T subcarinatus in the Senegal shells has a larger diameter but the rate of increase in size is less than in T attenuatus.

Distribution: The species is known from Senegal to Angola. Type locality: Pointe Noire, Congo.