Sporangia gregarious, globose, dull black, the peridium when present silvery, shining, or simply smooth, transparent and without iridescence, stipitate; stipe short, black, tapering rapidly upward, annulate with the persisting base of the peridium; columella short, thick, truncate, and widened at the top; hypothallus well developed, brown or purple; capillitium dense, made up of dark brown branches, numerous and rather slender, repeatedly branched and anastomosing toward the surface to form a slight delicate network with abundant free ends; spores dark purple brown, rough, 14-16 mu. This species in outward appearance resembles _L. physaroides_, from which it is easily distinguished by the much greater diameter of the globose sporangium, 1 mm. or more. The persistent base of the peridium is also characteristic, very prominent sometimes, and visible to the naked eye. The capillitium is also unlike that of _L. physaroides_; resembles more nearly that of _L. violaceum_. From the latter species _L. robustum_ is distinguished by the color of the peridium, and by the larger, darker spores and generally different capillitium. In our former edition this is called _L. sauteri_ Rost. That much-quoted author distinguished _L. violaceum_ and _L. sauteri_; the English authors make the last named a variety only of the former. This our American species is _not_. It is, as presented in our western mountains, clear-cut, well defined, not a variety of anything. The original name is therefore restored. _Lamproderma arcyrioides_ (Somm.) Morgan is probably a form of _L. columbinum_. The original _L. arcyrioides_ has not yet been certainly identified in North America; see following species. Colorado, Oregon, Washington, California. 3. LAMPRODERMA COLUMBINUM (_Pers._) _Rost._ 1796. _Physarum columbinum_ Pers., _Obs. Myc._, I., p. 5. 1875. _Lamproderma columbinum_ Rost., _Mon._, p. 203. Sporangia scattered, gregarious; rich violet or purple with metallic iridescence, globose, stipitate; the stipe long, three-fourths the total height, slender, subulate, black; hypothallus scant, purplish or brown; columella small, one-third the height or less, tapering or acute, black; the capillitium brown throughout, not dense, arising from nearly all parts of the columella, freely branching and anastomosing to an open, large-meshed network; spore-mass black, spores by transmitted light dark brown, rough, 10-12 mu.