Shell slender, solid, white, evenly tapered, with about thirteen moderately rounded, rather strongly sculptured whorls. Nucleus ? (missing in the type) ; longitudinal sculpture consisting, first, of five or six uniform strong rounded threads having a light yellowish color, which, when the shell is fresh, contrasts distinctly with the opaque whiteness of the rest of the surface; these threads pass over the transverse sculpture without nodulation, and are at a nearly uniform distance from each other, but the space between the posterior thread and the suture behind it is nearly twice as wide as the others; the remaining spiral sculpture is composed of very much finer, even, uniform rounded threads, four to six between each two large ones, and (on the last whorl) ten or eleven between the posterior strong thread and the suture; these are on the later whorls reticulated by similar but transverse threads, which pass over the whole sculpture from suture to suture, but which are obsolete or absent on the smaller whorls; in addition to these there are on each whorl about twelve strong rounded costae or elevated Waves, extending backward from the periphery of the base to the suture, which is coronated by their stout rounded terminations with the appearance of pits between them; these ribs have a slightly flexuous outline, and upon nearly every whorl there is one or more of them stouter, more elevated, and more oblique than the others, having the character of a varix; the base is rounded the basal area is small, margined by a strong rounded elevated thread under which the anterior ends of the transverse costae appear to be inserted, forming pits between them and rendering the outline of the basal surface somewhat stellate; within the margin there are one or two strong and numerous fine spiral threads, but the transverse sculpture seems obsolete; the aperture is rounded to the right, slightly flattened on the basal side, and narrowed behind; inside white and polished and with a slightly projecting margin behind which is the broad face of the thickened varix, over which the sculpture of the whorl is continued to meet the aforesaid margin; the aperture is entire, but the axis is imperforate and the whorls closely adjacent; the operculum is pale translucent yellow, of about three turns. Long. of shell, 11.0; of last whorl, 3.6; of aperture, 1.5; max. lat. of last whorl, 2.75; of the basal area, 1.5 mm.

Shell about 11 mm. (1/2 inch) in length, elongate, imperforate and strongly sculptured. Whorls IS, slightly convex. Nuclear whorls 3, smooth, pale amber in color. Color a light and dull brown to a dirty gray. Suture moderately impressed. Aperture subcircular. Outer lip much thickened and rounded. Columella short and arched. Axial sculpture consisting of 12 strong costae, the ends of which produce crenulations at the suture. Spiral sculpture consisting of 6 to 7 cords which are strong but much less so than the axial costae. Slight nodules are produced where the spiral cords pass over the axial costae. in addition there is an exceedingly fine reticulated sculpture between these costae and cords which, under 30x magnification, has the appearance of coarsely woven cloth. This latter character is invested in the superficial layer and may be lost in worn specimens. Basal area defined by a low and rather inconspicuous ridge beyond which the axial costae do not extend. The basal area, however, does have the fine reticulated pattern. Operculum corneous and paucispiral.

This beautiful little species has quite a different aspect from the S. crenulata group, to which it is most nearly allied. The yellowish color, which was quite marked when fresh, has in a year faded considerably, though the shell has not been exposed to the light. The operculum differs from that of the northern and extreme southern Opaline in being thin, yellow, and translucent, instead of opaque and black.

Opalia aurifila differs from O. eolis by being far more attenuated, having much less globose whorls and having fewer axial costae. The microscopic sculpture is similar in both species. In Opalia eolis the whorls are more shouldered and the crenulations do not always abut upon the whorl above. So far as the present records go the range in depth for O. aurifila is 55 to 170 fathoms and that for O. eolis is 23 to 94 fathoms.

Off Martinique

Range. From Hillsboro Inlet, Florida and south through the West Indies to Martinique.