Tulotoma Haldeman, 1840

Examined species: Tulotoma magnifica (Conrad, 1834) (Figs 2F, 3F, 6F).

Remarks: The operculum of Tulotoma can be easily distinguished from that of all other genera based on the following characters: semi-elliptical shape; inwardly folded opercular apex and opercular base; outwardly folded inner margin; a rough, nontransparent and small inner opercular region; and a wide, thin marginal region that obviously differs in colour from the enamel region, especially when it is compared with Rivularia Heude, 1890 . Like Tulotoma, Rivularia has a semi-elliptical shape and subcentral nucleus.