Sporangia scattered, dull grayish-yellow or gray, depressed-globose, umbilicate, minute, stipitate; the peridium comparatively thick, tenacious, especially persistent below, tawny or yellow; the stipe pale brown or orange, erect, even or slightly enlarged at base; hypothallus scant or none; columella prominent, more or less discoidal, rough, or spinulose, especially on the upper surface, yellow; capillitium not abundant, pale fuliginous, often branching and anastomosing so as to form a loose net; spores nearly smooth, dark violaceous by transmitted light, 8.5-9.5 mu. The species differs from _D. xanthopus_ in several particulars,--in the much firmer, more persistent, and less calcareous peridium, in the more complex capillitium, in the darker and larger spores, and especially in the peculiar and prominent columella, which is not only rough, but even "sometimes spinulose even to the extent of long spicules penetrating to one-third the height of the sporangia." _N. A. F._, 2493. As stated under No. 8, these last two species are called varieties only of _D. nigripes_. They are so retained in _Mycetozoa, 2nd ed._ Since, however, they are the usual presentation of the species in the United States, it seems wise to let them stand for the present, as here. They are quite distinguishable; _D. eximium_ especially well marked. Apparently rare, it yet ranges from New York to eastern Iowa, in colonies rather large. Okoboji Lake;--fine! 13. DIDYMIUM TROCHUS _List._ 1898. _Didymium trochus_ List., _Jour. Bot._, XXXVI., p. 164. Sporangia plasmodiocarpous, hemispherical or turbinate, white, sessile or very short-stalked, cream-colored or white; peridium double, the outer shell-like, the inner membranaceous, more or less adherent to the outer, both caducous together, leaving the thickened base surrounding an expanded columella; stipe, when present, very short, stout; capillitium colorless, nearly simple; spores brownish-purple, strongly warted, 9-10 mu. On decaying leaves, rotten cactus, yucca, etc., Monrovia, California; _Bethel_. Reported from England on beds of leaves or straw; in Portugal Dr. Torrend finds it on or _in_ dead leaves of _Agave americana_! Evidently an American species, and belonging to arid regions; its occurrence in England surprising! 14. DIDYMIUM ANNULATUM _Macbr. n. s._ PLATE XX., Figs. 4, 4 _a_.