Abstract: Sixty species of monogenetic trematodes (Dactylogyrus, Ancylodiscoides, Ancyro-cephaltts, Bychouskyella, Falciunguis and Gyrodactylus) parasitic on the commercial fishes of lake Hong Hu have been recorded in the present report. Two of them are considered as new species. They are charaterized as follows:1. Dactylogyrus ungulatus sp. nov(Fig. 1.)Body of small size, being 490-860 μ long and 93-150 μ in width.Marginal booklets 13-21 μ.. Total length of central large anchors 23-29 μ, basal portion 12-21 μ, point 6-12 μ, inner root 6-11 μ, outer root 1-4 μ. connective plate 2-3 × 16-25 μ.Copulatory tube 42-49 μ in length. Supporting apparatus, with swollen base and three claw-like projections on extremity, measuring 29-34 μ. Vagina and eggs have not been discovered. Description based on 10 specimens.Types: Deposited in the Department of fishery, Central China Agricultural College and in the author's collection.Host:Xcnocypris argentea.Location: Gill.Distribution: Middle Yangtze valley (Jiayu, Lake Hong-Hu, Hubei Province).Remarks: This worm is rather similar to Dactylogyrus chondrostomi Malewitzkaja 1941 and D. cordus in the shape of the central large anchors, but it differs from the latter by the shape of male copulatory organ and the size of cuticular structures.2. Gyrodactylus honghuensis sp. nov.(Fig. 2.)Body of small size, being 190-240 μ long and 39-50 μ wide. Pharynx 15 × 14-16 μ and opisthnhaptor 50-67 × 40-50 μ in size. Marginal booklets are of ordinary type; total length 23-24 μ, handle 17-18 μ, point 5 μ.Total length of anchors 44-52 μ; the basal portion 33-39 μ, inner root 14-21 μ, point 16-20 μ. Connective plate of the outer root small, ligament-like, 2 × 14-17 μ in size, basal connective plate 4-5 × 24-27 μ.Male copulatory organ 12 × 11 μ in diameter, cirrus bulb with five large spines and two minute spines.Host: Erythrocultrr dabryi.Location: Gill.Loeality: Lake Hong-Hu, Hubei Province. Types: Deposited in the Department of Fishery. Central China Agricultural college. Description is based on 10 specimens.Remarks: This worm is similar to G. sprostonae Ling, 1962 but it differs from the latter by the structure of the male copulatory organ and size of basal connective plate.