SUMMARYA new genus and species of fungus,Uredinella coccidiophaga, intermediate between the rusts andSeptobasidiumis described. The fungus produces a small, discoid, compact, annual growth which covers and is nourished by one scale insect, forming within the insect's body haustoria of theSeptobasidiumtype. After producing spores in the spring, the fungus dies. Brown, thick-walled teleutospores are formed which in nuclear behavior, and external structure strikingly resemble the teleutospores of certain rusts. The basidia are four-celled and each cell is uninucleate at first. Before the spores are formed, nuclear division occurs in each cell. One nucleus goes into each spore and one remains with some cytoplasm in each sterigma. In water, the spores each produce a sterigma and another spore, the nuclear behavior in the basidial cells being repeated. In addition to the teleutospore, another type of spore is formed. This resembles the teleutospore in color and wall structure and resembles some of the teleutospores in being cylindrical in shape. It differs from the teleutospores in being binucleate and in producing a long, bent-elliptic, binucleate spore. The latter is regarded as a uredospore and the spore that bears it as a uredospore mother cell.