The chytridiaceous hyper-parasite R. marina penetrates into the host fungus by a minute penetration peg. Following infection the host cytoplasm exhibits a centric or eccentric clear area which is presumably the sporangial rudiment of the invading hyperparasite. The sporangia of the hyperparasite conform to the shapes of the host sporangia, although some distortion of the host is effected. This is the 2nd record of R. marina.