« Shell small, thin, yellowish or grayish, with ten ordinary and three polished dark brown smooth nuclear whorls; apex acute, whorls well rounded, suture distinct; whorls closely reticulated by (on the last about twenty-five) little-elevated thin transverse lamellae, and five strong, even, regular revolving or spiral ribs over which the lamellae are fluted and frilled with great regularity. The lamellae pass from the suture to the margin of the very large basal disk, over the edge of which they pass as slightly raised lines centring at the axis of the shell, and giving a wheel-like appearance to the disk, which is also sculptured by fine radiating and stronger revolving threads; the disk is a little concave, and like the rest of the shell tinged with brownish yellow, but the columella or axis is pure white, polished, and shows a single strong spiral fasciole; the lip is thin, hardly at all reflected, the margin is angulated by the carina of the disk and at the somewhat projecting columella so that the aperture has a squarish appearance. The whole base from the suture down is occupied by the disk. » – W. H. Dall: “Reports on the results of dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Caribbean Sea (1879-80), by the U.S. Coast Survey Steamer "Blake", Lieut.-Commander C.D. Sigsbee, U.S.N., and Commander J.R. Bartlett, U.S.N., commanding. XXIX. Report on the Mollusca. Part 2, Gastropoda and Scaphopoda”, Bulletin of the Museum of Comparative Zoölogy at Harvard College vol. 18, Cambridge 1889, p.312.

Notice the concave base, devoid of longitudinal lamellae after the passing of the abapical ridge (an anterior spiral bead that is usually sunken in the suture). Original pictures provided by P. Sharp, Denver Museum of Nature & Science Marine Invertebrate Collection, for GBIF – (CC BY-NC).