General description (after 232 shells from 14 localities). — The shell is slender, sometimes more compact, cylindrical. Only the largest specimens are somewhat conical. The top is rather blunt. The protoconch is of type B, occasionally tending to C. There are five to seven flat to slightly convex teleoconch whorls. The suture is inclined, narrow and rather deep, or more wide and shallow. The ribs are clearly marked and not very broad. Dependent on the number of ribs (very variable), the interstices are as broad as, or broader than, the ribs, but smaller interspaces do occur as well. The ribs are vertical, or more or less inclined to the right, straight or, at least on the last whorl, sinuous. They end abruptly at the periphery of the last whorl, but often they continue, decreasing and disappearing or not, towards the base of the shell. The initial whorls have one spiral just above the abapical suture. In a single case we observed a second spiral on the penultimate whorl, which is practically incorporated into the suture. The last whorl has two spiral ridges, both just above the aperture, close to each other, the lowest one rather as a conclusion of the ribs than a real spiral. If, nevertheless, the ribs do continue in any form, then there are two normal spiral ridges. The aperture is narrow egg-shaped with a significant tooth. There is at best an umbilical chink.
Length 2.0-3.7 mm, LW 41-58%, A 24-33%, L/B 2.5-3.2, B/b 1.2-1.5 (based on 18 shells).

Although C. nanodea shows some resemblance with C. terebellum there are remarkable differences. C. terebellum has flat whorls and its broader and straight ribs are inclined more to the right. C. terebellum is more conical in its initial whorls and has a more pointed top, its protoconch is less coiled. For the differences with Turbonilla, cf. C. terebellum. Although C. indistincta is generally smaller, individual specimens may strongly resemble in shape and rib-pattern the shells of C. nanodea with flexuous ribs. The much larger number of spirals on the whorls and the absence of a tooth in C. indistincta are decisive. C. sigmoidea could be confused with larger specimens of C. nanodea, but C. sigmoidea has no tooth, a very flat and blunt apex, and spiral striae (no real spirals) over the total height of all whorls.
Although, as Van Aartsen mentions, C. nanodea can grow to a larger size than C. suturalis, one often sees specimens of about the same length. Nevertheless, C. suturalis has (much) finer ribs, close together, the initial whorls are somewhat longer and particularly the tooth (rather a pleat) is only visible on turning the shell, whereas C. nanodea has a clearly visible tooth.

From NW. Spain south to the Mediterranean.