Genitalia of Amphidromus spp A, B Amphidromus haematostoma Möllendorff, 1898 from Ba Chien, Pakse, Champasak, Laos (NMNS-8764-061), showing A general view of genitalia B interior structures of penis and vagina chamber C, D Amphidromus madelineae Thach, 2020 from Duy Xuyen, Quang Nam, Vietnam (NMNS-8764-110), showing C general view of genitalia D interior structures of penis and vagina chamber. Red dots indicate the shape of the missing gametolytic sac. Green arrows indicate the genital openings. Abbreviations: e, epiphallus; fl, flagellum; fo, free oviduct; gd, gametolytic duct; gs, gametolytic sac; ov, oviduct; p, penis; pp, penial pilaster; pr, penial retractor muscle; pv, penial verge; v, vagina; vd, vas deferens; vp, vaginal pilaster.