SUMMARY
The taxonomy and morphology of the myxomycete genus Echinostelium are presented, along with a key to the species. Members of this genus have minute, stipitate sporangia, and they are often encountered on the bark surface of living trees or dead plant materials in moist-chamber culture. Four new species, E. apitectum, E. brooksii, E. corynophorum, and E. paucifilum are described. Thirteen species are recognized, and detailed descriptions of each are provided. Illustrations of 12 of these species are included.