While isolating fungi from soil samples obtained in the South Pacific area by Dr. L. S. Olive in 1956, the writer discovered an interesting phragmosporous fungus with white mycelium. Upon attempting the identification of this organism, it was soon found that, while quite definitely related to the genus Mastigosporium, the organism was considerably different from all known species (Hughes, 1951). Only one species of Mastigosporium was found to appear similar to the new organism, that being Mastigosporium rubricosum (Dearn. and Barth.) Sprague. Sprague (1938) briefly described the colonies of M. rubricosum (= M. calvum) on various media. Only on Mix's agar was the colony white. In all cases the colonies were flattened, leathery, and wrinkled. The new organism, on several agars tested (Czapek's, potato-dextrose, and rose-bengal-streptomycin agars), formed floccose, rapidly spreading, white colonies with an abundance of spores. Only on corn meal agar (with 0.1% yeast extract) was the mycelium partially submerged, but even in this instance, the conidiophores were scattered over the whole mycelium, and not clumped as described as being characteristic of the genus. Growth on potato-dextrose agar was rapid, single-conidial inoculation reaching a diameter of one centimeter in 48 hours and 3-4 centimeters in one week, as contrasted to the much slower growth of previously described species. In the description of the latter, no mention was made of any production of chlamydospores. The new organism, after some time in culture, produces 1-3-celled chlamydospores of rather striking appearance. While the conidia of both M. rubricosum and the new organism are usually three-septate, the size of the spores differs considerably. Bollard (1950) lists spore measurements as follows: