Neothauma E. A. Smith, 1880

Examined species: Neothauma tanganyicense E. A. Smith, 1880 (Figs 4G, 5G, 7G).

Remarks: Apart from Mekongia, the monotypic genus Neothauma can be distinguished from other genera with a concentric inverted-comma-shaped operculum by the following combination of characters: height clearly larger than width and a small nuclear region that is relatively rough, with many shiny grains or veins.