A new species of the myxomycete genus Perichaena is described in this paper. The new species, named Perichaena calongei, was found during intensive studies of arid areas of the Monte desert in Argentina. It has been found directly in the field from the provinces of Catamarca, La Rioja, Salta and San Juan, in the Northwest of Argentina, and isolated from moist chamber cultures of native plant species collected in Catamarca, Jujuy, Salta and San Juan. The characters that make this species unique in the genus are the combination of the morphology of the sporocarps, the structure and dehiscence of the peridium, and the ornamentation of the capillitium. The morphology of the my xo - mycete specimens was examined using light microscopy with Nomarski interference contrast, and scanning electron microscopy. Micrographs of relevant morphological characters are included. A key to facilitate the identification of the stipitate species of Perichaena is also proposed.