A monogenetic trematode Polystoma hakgalense sp. nov. is described from the urinary bladder of the frog Rhacophorus cruciger eques, from the Hakgala Strict Natural Reserve (1 707 m). The following combination of characters distinguishes it fromm all other species of the genus: the random and reticulate anastomoses of the gut, the entire nature of the base of the opisthaptoral hooks, and the lack of vitellaria in the spaces between the opisthaptoral suckers. Acanthocephalus serendibensis is redescribed after a study of the original type specimens, and of fresh specimens from the horn-nosed lizard Ceratophora stoddarti from the Hakagala S.N.R. and from the gecko Cnemaspis kandianus kandianus from Haputale (1 418 m). The gecko is a new host record for A. serendibensis. The original description has been modified as regards the proboscis, which carries 10-12 longitudinal rows of hooks with 3-4 hooks in each row, the embryo within the egg, which bears minute spines over its body-surface and a row of hooks at one end, and the bursa of the male, which lacks bursal rays.