Polystomoides nelsoni sp. n. Ventral view of holotype; the dotted line indicates the outline of the vitellarium. Abbreviations: eg, egg; gb, genital bulb; ha, hamulus; hp, haptor; ic, intestinal caecum; mo, mouth; ov, ovary; ph, pharynx; su, sucker; te, testis; va, vagina; vd, vas deferens; vi, vitellarium; vt, vitelline duct. Scale bar: 1 mm.