A new species ofPetalosporus, P. anodosus, is described and illustrated. Two isolates representing this species were isolated from dung in California. The new species differs from the only other species of the genus,P. nodulosus, by the lack of thick-walled peridial hyphae with enlargements at the septa and by the absence of disarticulation of peridial elements. Peridial hyphae inP. anodosus have walls which are somewhat thickened and the cells are often variable in diameter. Conglomerate ascospores usually assume the petaloid arrangement characteristic of the genus.