Shell very small, conical, sharp-tipped, with a lop-sided base, subscalar, ribbed, and with spiral threads; there is a strong labral varix, with a small, deep, round sinus. Sculpture: Longitudinals: there are on the last whorl about thirteen rounded, rather weak, slightly oblique longitudinal ribs, which extend to the snout; on the fifth and sixth whorls they are fewer, but rather stronger; on the fourth whorl they are lamellar; they are parted by shallow open furrows of fully two-thirds their breadth. The whole surface is covered with microscopic but coarse hair-like lines of growth. Spirals: there are 25 to 30 close-set, flatly rounded, alternatingly stronger and weaker spiral threads, of which those on the shoulder and base of the last whorl are the weakest; those (twelve in number) in the middle of the body are broadest; those on the snout are the most prominent, especially the highest three; of the group on the body, the highest which comes in below the sinus-area forms a very slight keel to the whorls. Colour buff. Spire subscalar, high, conical. Apex consists of 1 ½ embryonic whorls, which rise regularly to a high, fine, rounded point, the extreme tip of which is quite prominent. Whorls 7, of regular increase, high and rather narrow, very slightly carinated, convex; the last is long and narrow, nearly cylindrical in the middle; on the right side the base is scarcely contracted; but on the left side it is cut off with a long, oblique, and very considerable truncation, and is in this way very lop-sided. Suture not deep, but distinct and im¬pressed. Mouth long and narrow, with nearly parallel sides; the short open canal is of the same width and direction as the mouth itself, and ends in a rather deep nick; the sinus above is about half the width of the mouth, from which it turns off through the thick lip very obliquely, and is funnel-shaped. Outer lip in direction oblique and almost straight, a very little inflected, thick, its front face roundly bevelled off to the inner side, and its two sides parallel; it is strengthened by a strong external rounded varix, which extends to the front of the very short snout but not to the pillar; internally there is a alight pad faintly scored by very obscure teeth, but terminating in a single, small, rounded, and rather prominent tubercle on the lower side of the sinus. Inner lip very narrow and thin, but with a thickened pad between the sinus and the body-whorl; its direction is oblique, a little concave above; it is very straight on the pillar. H. 0.152 inch B. 0.06 inch. Penultimate whorl, height 0.028 inch. Mouth, height 0.078 inch, breadth 0.019 inch.

This species resembles a good deal a very small and refined Mangelia rugulosa, Philippi, having the same lop-sided base; but that species has the right side of the base somewhat more obliquely truncated; so that there is much less of inequality between the two sides than in this Challenger species, which is also slimmer, has the sculpture both of ribs and spirals very much finer, the apex much smaller and higher, the suture less deep, and the nick of the canal in front very much more distinct.

Brazil. Off Pernambuco.