Cap 1.5-5.0 cm broad, subglobose to convex-depressed; margin incurved, typically remaining attached to the stipe at maturity; surface viscid when moist, otherwise dry, covered with light-brown to ochre-brown, appressed fibrils over a cream-buff background, fading in age; context up to 5.0 mm thick at the disc, elsewhere thin, pallid, or yellowish- tawny where injured; odor strongly aromatic, described as similar to "bubble-gum;" taste mild.
Gill tissue consisting of crumpled, dull brown to dark reddish-brown plates and small, irregularly shaped chambers.
Stipe present or absent; when present 0.5-2.5 cm long, 0.5-1.5 cm thick, short, tough, equal to pinched at the base; surface white, glabrous to cottony-fibrillose; context white, sporadically brown to rusty-brown where injured; veil whitish, membranous, inelastic, with ochre to light-brown fibrils, usually remaining fused to the stipe; annulus absent.
Spores 7.5-9.0 x 5.0-7.0 µm, elliptical, smooth, moderately thick-walled, with an apical germ pore; spores dull brown.
Solitary to scattered on conifer wood in montane areas; fruiting during the spring shortly after snow-melt; common.
Nivatogastrium nubigenum is a common snowbank species, distinctive because of its secotioid development and lignicolous habit. Typical of secotioid species, the cap usually remains attached to the stipe at maturity, while the "gills" consist of crumpled tissue, no longer capable of producing a spore print. Species from a number of gilled mushroom genera have adopted this type of development, presumably an adaptation to the dessicating conditions often seen in the Sierra. Thaxterogaster pingue is similar, but fruits in the fall, is terrestrial, and lacks a strong aromatic odor.