Shells minute, coiled, translucent, operculate. Whorls very flattened axially. The very young parts of the shell can bear some radial sculpture. Identification keys for most of the species can be found on the Shelled Heteropod Identification Portal.
 

The shell bears a calcitic keel at the periphery; « outer lip of the aperture always more or less fissured » (J. J. Tesch: “Systematic monograph of the Atlantidae”, Notes from the Leyden Museum vol. 30(3), Leyden 1908, p.4). Operculum horny, « vitreous, thin, fragile, bearing the muscle impression in its center » (S. Rang: Manuel de l'histoire naturelle des mollusques et de leurs coquilles, Paris 1829, p.123).
 

« Shell subcartilaginous, quickly convolute ; the first whorls being nearly enveloped hy those succeeding, discoid, symmetrical, deeply umbilicated on each side; last whorl broadly and sharply keeled from the edge of the mouth to about half the circumference; keel angular at its posterior termination; aperture sinuous, heart-shaped, not entire, being encroached upon by the preceding whorl; peiitreme acute, with a narrow slit or sinus on the front edge, running into the keel, which is there double. Operculum heart-shaped, depressed, and channeled with a medial line. » (W. H. Benson: “Account of Oxygyrus a new genus of pelagian shells allied to the genus Atlanta of Lesueur, with a note on some other pelagian shells lately taken on board of the ship Malcolm”, Journal of the Asiatic Society of Bengal vol. 4, Calcutta 1835, p.174). The genis is monotypic.
 

Shell minute, translucent, with about four whorls rapidly increasing in diameter, « though not in the proportion as in Atlanta » (J. J. Tesch: “Systematic Monograph of the Atlantidae (Heteropoda) with enumeration of the species in the Leyden Museum”, Notes from the Leyden Museum vol. 30, Leyden 1908, p.9). The early whorls are coloured and rise above the last whorl. Presence of a cartilaginous keel, often damaged, very often wanting as on the specimen hereunder pictured.