Abstract: The present paper deals with a new species of the genus Myxobolus parasitizing the fish(Carassius auratus auratus)in Beibei, Chongqing, China. Type specimens are deposited in College of Life Sciences, Southwest China Normal University. All measurements are in microns. Myxobolus beibeiensis sp. nov.(Figs. 1—4)Host Carassius auratus auratus(Linnaeus). Location gill. Locality Beibei(29°49′ N, 106°25′ E),Chongqing. Date Aug. 16, 1996. Vegetative form is not being observed. Spore in shape of pumpkin seed in thecal view, with blunt and rounded posterior end, tapering to anterior extremity, with widest part in field from half level to anterior two-thirds level of body, and with 3—4 small V shaped folds on posterior part in some spores; convex lens shaped in sutural view, sutural ridge distinct and straight; two short rod like polar capsules not equal in size, with a triangular or round nucleus behind them, and their anterior extremities not on the same level, larger polar capsule occupying two-fifths of spore length; sporoplasm concentrated, with two round germinal nuclei and an iodinophilous vacuole. Dimensions of spores preserved in formalin(5% in Concentration): length 17.2(16.0—19.1), width 11.5(10.2—13.0), thickness 8.0(7.1—9.5); larger polar capsules 8.8(8.2—9.7)by 3.3(3.2-3.4), smaller polar capsules 7.8(7.5—8.0)by 3.0(2.8-3.2). This species is similar to Myxobolus tayehensis Chen, 1998, but differs from the latter in following respects:(1)spores of the new species are in the shape of pumpkin seed in thecal view, while spores of M. tayehensis are pyriform or bulb shaped;(2)the two polar capsules of the new species are not equal in size, and the larger one occupies two fifths of the spore length, while those of M. Tayehensis are equal in size, and occuping one half of spore. This species also resembles M. orientalis Schulman, 1962, but differs from the latter in two respects.(1)Spore length of the new species in about one and half times as long as spore width, while that of M. orientalis is twice as long as spore width.(2)The two polar capsules of the new species are unequal in size, and the larger one occupies two fifths of the spore length, while the latter possesses two equal polar capsules, the length of which is two thirds to three fourths of spore length.