Genitalia of Amphidromus spp A–C Amphidromus bozhii Wang, 2019 from Tuy Hoa, Phu Yen, Vietnam (NMNS-8764-016), showing A general view of genitalia B interior structures of penis C Interior structures of vagina chamber D, E Amphidromus placostylus Möllendorff, 1900 from Dak Po, Gia Lai, Vietnam (NMNS-8764-217), showing D general view of genitalia E interior structures of penis and vagina chamber. Red dots indicate the shape of the missing gametolytic sac. Green arrows indicate the genital openings. Abbreviations: ap, appendix; e, epiphallus; fl, flagellum; fo, free oviduct; gd, gametolytic duct; ov, oviduct; p, penis; pp, penial pilaster; pr, penial retractor muscle; pv, penial verge; v, vagina; vd, vas deferens; vp, vaginal pilaster