Shell slender, acute, whitish or yellowish, of about fifteen whorls ; nucleus flattened, sharply keeled, white, polished ; first nuclear whorl with two keels, on the third an intercalary thread appears, all of which quickly become sub-equal and uniformly nodulated ; sculpture of three spiral rows of tubercles with their anterior (basal) slopes moderate, but the posterior (spireward) slope nearly perpendicular to the axis, so that the tubercles point more or less spire-ward ; the posterior row, just in front of the suture, is a little more prominent than the other two, and so marks the whorls, which are somewhat obliquely coiled ; the tubercles are arranged on the whorls obliquely from right to left, and connected by the representative of the nuclear keels, with the spaces between the spirals deep and narrow, that space in which the suture is contained being only distinguishable from the others by the above-mentioned more prominent spiral ; the suture itself, even with a good glass, is hardly to be made out ; base flattened or in the perfectly mature shell rounded, in the first case with one, in the latter case with three well-marked spiral threads and evident radiating lines of growth ; pillar stout, straight, with a thick solid but small lump of callus on it; aperture small and narrow ; both canals probably closed, reflected and rather short. Length of shell, 8,25 mm; of last whorl, 2.0 mm; of aperture, 1.0. mm. Max. lat. of shell, 1.75 mm ; of nucleus, 0.5 mm.

Without careful study the differences between the forms of this group are hardly noticeable. When examined under a high power it is soon found that species which to the naked eye appear very similar or hardly distinguishable are really characterized by quite a different method in their sculpture, though the general result may be not very dissimilar in its salient features. The tubercles of one are due to grooves cutting transverse riblets; of another, to spiral ridges rising to nodules on the riblets ; of a third, to rows of nodules side by side without spiral or transverse sculpture of any kind. This and the following forms have been separated after several days' close study from an assembly which the first examination had almost decided to place in the category under one specific name. However, there are distinct definable differences between them, and the fact that the microscope is required to perceive these differences should have no effect on our estimate of their systematic value.

Gulf of Mexico and Caribic. Yucatan Strait, 040 fms. Cuba: Off Cape San Antonio.