Angulyagra Rao, 1931 Examined species: Angulyagra cf. polyzonata (Frauenfeld, 1862) (Figs 4T, 5T, 7T). Remarks: Apart from Notopala, Angulyagra can be distinguished from other genera with a concentric inverted-comma-shaped operculum by the following combination of characters: a relatively small nuclear region with shiny grains or veins, a relatively thick enamel layer and a thin marginal region that obviously differs in colour from the enamel region. One species of Angulyagra (total of three specimens with operculum) has been examined for this study (Table 1).

Published as part of Zhang, Le-Jia & von Rintelen, Thomas, 2021, The neglected operculum: a revision of the opercular characters in river snails (Caenogastropoda: Viviparidae), pp. 1-14 in Journal of Molluscan Studies (eyab 008) (eyab 008) 87 (2) on pages 7-8, DOI: 10.1093/mollus/eyab008, http://zenodo.org/record/15098489