Nematobothrium spinneri sp. n. is described from cysts in the body musculature of Acanthocybium solandri (Cuvier) caught near Brisbane. It differs from other members of the genus in that the testes, ovary, and vitellaria show multiple branching, the vitellaria extend anteriorly as far as the testes, and the uterus descends on leaving the ootype. In addition, the posterior part of the worm is retractile. Neometadidymozoon helicis sp. n. was recovered from cysts in the walls of the buccal cavity of Platycephalus fuscus Cuvier and Valenciennes caught near Brisbane. It differs from N. polymorphis, the only other member of the genus, in that it is smaller, constant in shape, its testes do not extend into the forebody, and the uterus forms 3 rather than 2 loops. Wahoo, Acanthocybium solandri (Cuvier), caught off the Queensland coast frequently carry bluish cysts in the flesh. According to fishermen, about one-third of the wahoo are affected, and partly for that reason, the value of wahoo flesh on the local market is half that of other scombrid fish. The cysts are caused by a new didymozoid trematode species which is described below. This is followed by a description of a second new didymozoid from the buccal cavity of local flathead Platycephalus fuscus Cuvier and Valenciennes. Didymozoids so far recorded in Australia are Nematobothroides australiensis Nikolaeva and Korotaeva 1970 from the gonad of Scomber australasicus, and Nematobothrium filiforme Yamaguti 1934 from the gills of the same fish (Korotaeva, 1974). MATERIALS AND METHODS Twenty-one cysts from A. solandri were collected from fish caught off Point Lookout, Queensland, in February 1978. Five live worms were teased out, fixed in hot 10% formalin or flattened and fixed in cold formalin, and stained with hemalum. Twenty infected flatheads P. fuscus were obtained from Moreton Bay, Queensland, in March 1978. Worms were treated as above or sectioned and stained with hematoxylin and eosin. Measurements are in mm unless otherwise indicated. Nematobothrium spinneri sp. n. (Figs. 1-7)