Shell depressed, with five whorls, somewhat flattened above and below ; nucleus small, translucent white, and with the two first whorls polished, smooth or marked only by faint growthlines; remainder of the whorls with a narrow puckered band revolving immediately below the suture, on which the shell matter is as it were pinched up into slight elevations at regular intervals, about half a millimeter apart. In some specimens, outside of this band an impressed line revolves with the shell ; remainder smooth, shining or with evanescent traces of revolving lines impressed from within and strongest about the rounded periphery ; base rounded toward the umbilical carina over which it seems to be drawn into flexuously radiating well-marked plications (about thirty-two on the last turn) which disappear a third of the way toward the periphery ; walls of the umbilicus concave, overhung by the carina, turns of the shell so coiled that the part of each whorl uncovered by its successor forms a narrow spiral plane ascending to the apex like a spiral staircase or screw thread. Pillar straight, thin, with no callus ; aperture rounded except at the angle of the umbilical carina; margin thin, sharp, not reflected or thickened ; no callus on the body whorl in the aperture ; shell whitish or greenish; nacre less brilliant in dead or deepwater specimens; with zigzag brown lines variously transversely disposed and disappearing on the base. Alt. 4.0. Maj. diam. 6.75 ; of umbilicus, 1.75 ; of aperture, 2.5 mm.

The operculum is like that of Gaza, and has six or seven whorls. None of the specimens show any tendency to a reflected lip, yet it is, of course, possible that no completely adult specimen was obtained. The animal has a short stout foot, bluntly rounded at either end. It is of a pinkish tint. The tentacula are very long and the eyes large. The muzzle is rounded and not very long, its extremity plain. There are no frontal lobes. The epipodium has a very small anterior lobe with a cirrus behind it, then a space without cirri, a long process just in front of the opercular disk, and one, shorter, under it on each side, making three in all. There is no posterior point to the epipodium, and only the above three cirri on each side. The jaw is somewhat like that of Umbonium, but shorter and broader. The radula, however, bears no resemblance to that of Umbonium (Rotella Lam.). The teeth are very elegant. The rhachidian tooth in general form (except the cusp) not unlike that of Calliostoma granulata Born (Troschel, II. pi. xxiv. fig. 18), but the central spur of the cusp is long and slender like a stiletto, extending considerably behind the posterior edge of the base of the tooth. On each side of it are four stout sharp rather short denticles, radiating as from the median point of the front edge of the cusp. The laterals recall those of Gibbula divaricata, but have more, larger, and stronger denticles, all on the posterior edge of the cusp, or the edge away from the rhachis. The uncini are rather few in number, the cusps sword-shaped, sigmoid, the inner ones denticulated on both edges. The number of laterals is five. The radula as a whole is very short and small.

Description.—"Shell depressed, with five whorls, somewhat flattened above and below; nucleus small, translucent white, and with the two first whorls smooth or marked only by faint growth-lines; remainder of the whorls with a narrow puckered band revolving immediately below the suture, on which the shell matter is as if it were pinched up into slight elevations at regular intervals, about half a millimeter apart. In some specimens, outside of this band an impressed line revolves with the shell; remainder smooth, shining or with evanescent traces of revolving lines impressed from within and strongest about the rounded periphery; base rounded toward the umbilical carina over which it seems to be drawn into flexuously radiating well-marked plications (about thirty-two on the last turn) which disappear a third of the way toward the periphery; walls of the umbilicus concave, overhung by the carina, turns of the shell so coiled that the part of each whorl uncovered by its successor forms a narrow spiral plane ascending to the apex like a spiral staircase or screw thread. Pillar straight, thin, with no callus; aperture rounded except at the angle of the umbilical carina; margin thin, sharp, not reflected or thickened; no callus on the body whorl in the aperture; shell whitish or greenish; nacre less brilliant in dead or deep-water specimens; with zigzag brown lines variously transversely disposed and disappearing on the base." (Dall, 1881.)
Geographic distribution.—The southeastern Gulf of Mexico, the Straits of Florida occasionally as far north as Key Largo, Cuba and south through the Antillean arc.
Bathymetric range.—The possible range is 46 to 1472 m, but most commonly occurring in 100 to 200 m.
Remarks.—This is a beautiful species occurring rather commonly in depths less than 200 m. Microgaza rotella rotella is the southern form of this species, occurring occasionally as far north as Key Largo. The area from roughly Key Largo to off Miami is the transitional area between the 2 subspecies, with intermediate forms occurring commonly. North of Miami the subspecies inornata is found exclusively, and south of Key Largo only true rotella is taken. This indicates that true geographic subspecies are involved and not mere individual or population variation. The distinguishing character of true rotella is the presence of a row of elongate beads just below the suture line. The other subspecies, inornata, lacks these pustules;

The depressed form and marginated suture, as well as the kind of coloration, in this shell recall Umbonium. The texture of the shell and the character of its umbilicus are precisely as in Callogaza. The soft parts indicate its place to be in that vicinity- Until a larger number of the myriad of species shall have been examined, it is evident that the characters of the dentition in their classification cannot be formulated except in a provisional manner.