These shells have a relatively large, domeshaped protoconch with a smooth, blunt nucleus, but later developing brephic axial threads and fine spiral striae. The operculum is horny, ovate and paucispiral, occupying about half the area of the aperture, and the radula has a tricuspid central tooth and bicuspid laterals. The radula resembles that of Pareuthria except for the form of the laterals, which have the cusps set closer together, the inner one massive and incurved. A similar style of radula occurs in the species Notoficula problematica n.sp., described following.
I have included in Tromina a group of smaller Magellan species with rounded whorls and numerous regular spiral cords, crossed by weak axial threads, but they lack the prominent keels of both the genotype and the Clarence Island tricarinata. The protoconch, operculum and radula, however, are similar to those features in the typical species