SUMMARYThirteen soil isolates ofArthroderma lenticularumwhich possesses aTrichophyton terrestreimperfect stage, and aArthrodermaperfect stage were obtained.A. lenticularumwould not mate with any knownArthrodermaspecies, but exhibited complete intraspecific compatibility. It therefore fulfilled the primary criterion of a biological species.The most reliable method for identification and separation of it fromA. quadrifidumwas that of mating incompatibility.MorphologicallyA. lenticularumpossesses theT. terrestreconidial form and the symmetrically dumb-bell shaped peridial cells ofA. uncinatum.It is further distinguished by its yellow pigmentation.