Sporangia globose and sessile or plasmodiocarpous, dull yellow, smooth or scaly; peridium double, the outer wall densely calcareous, separating irregularly from the membranous inner wall; capillitium densely calcareous, the nodes large, more or less branched, yellow; spores purple brown, closely and minutely warted, 9-14 mu. This species is based by its author upon a gathering made in California by Dr. Harkness and named by Phillips who received it in England, _badhamia inaurata_. He seems not to have described it. Since its first appearance, the form has been found repeatedly in the Juras. Specimens are before me from Mt. Rainier believed to be the same. The plasmodiocarpous habit and yellow capillitium separate this from related _P. contextum_ and _P. mortoni_. Europe, California, Washington. 8. PHYSARUM DIDERMA _Rost._ PLATE XVIII., Fig. 9. 1875. _Physarum diderma_ Rost., _Mon._, p. 110. 1898. _Physarum didermoides_ var. _lividum_ List., _Jour. Bot._, XXXVI., p. 162. 1899. _Physarum diderma_ Rost., Macbr., _N. A. S._, p. 30. 1911. _Physarum testaceum_ Sturgis, List., _Mycetozoa, 2nd ed._, p. 79. Sporangia snow-white, clustered, sessile or narrowly adnate, globose or polygonal by mutual compression; peridium double, the outer dense, fragile, thick, calcareous, the inner delicate, remote, translucent, capillitium well developed, the calcareous nodules white, rounded or angular, sometimes uniting to form a pseudo-columella; spore-mass black; spores purplish, distinctly rough, 10-12 mu. A beautiful and distinct species. As others in the group with which it is here associated, it is a physarum with the outward seeming of a diderma. It occurs in Europe, therefore it is safe to assume that Rostafinski saw it. So well marked it is that any good description will define it, and Rostafinski describes it perfectly, adequately.[23] Mr. Lister having used for another species the name we here apply--see under _P. bitectum_--referred this present form to _P. didermoides_ Rost., _l. c._ Professor Sturgis, convinced that such reference was at least doubtful, gave to our American gatherings the distinctive name above, citing specimens from Massachusetts, from Colorado, and from California. Curiously enough he also includes specimens of _R. didermoides_ var. _lividum_ List., sent from England! Rare! Certainly rare in Europe and so far seldom seen in the United States, though widely distributed. Specimens are before us from Ohio, Michigan, Iowa, Oregon. No doubt the mountains of the north Pacific coast, a region to-day almost unsearched, will yet afford the species in abundance.