A new species P. megasporum, isolated a number of times from prairie soil in So. Wisconsin and from heath soil in Suffolk, England is described. This species is apparently a normal component of the mycoflora of certain grassland ecological habitats. It is characterized by unusually large, coarsely echinuiate conidia averaging 6.5[mu] in diameter, produces divaricate penicilli and is assigned to the P. nigricans series of the section Asymetrica-Divaricata.