Trochotaia Brandt, 1974

Examined species: Trochotaia trochoides (Martens, 1860) (Figs 4P, 5P, 7P).

Remarks: Trochotaia can be distinguished from the other genera by a concentric inverted-comma-shaped operculum that exhibits the following combination of characters: a thick, rough layer with many grains or veins over the whole of the inner opercular region; a clearly convex outer margin; and a smooth enamel region with a dense ray-like pattern.