CAP 4–10 (15) cm across, convex to broadly convex, occasionally expanding to plane; margin incurved at first, becoming plane or uplifted in age. Surface dry, covered with recurved scales becoming more matted-fibrillose in age; margin often with whitish veil remnants. Buff to honey brown, covered with slightly darker brown or yellow-brown scales. GILLS narrowly attached, often seceding, close to crowded, narrow, partial gills numerous. Gray to lilac-gray, becoming deep brown as spores mature. STIPE 5–10 cm long, 1–3 cm thick, more or less equal. Surface dry, covered with recurved scales below veil. Base often with white rhizomorphs. White to pale buff, at lower portion often with pale orange scales, and discoloring orangish in age. PARTIAL VEIL membranous, adhering to cap margin and forming a short skirt- to collar-like ring on stipe, collapsing or disappearing in age. FLESH thick, soft, whitish. ODOR mild to unpleasant, rancid. TASTE slightly disagreeable. SPORE DEPOSIT dark purple-brown. MICROSCOPY: Spores 6–8 x 4–5 μm, ellipsoid, smooth, thick-walled, grayish brown in KOH. Cheilocystidia 20–40 x 5–15 μm, nearly cylindrical to spindle shaped, smooth, with yellow contents in KOH.
ECOLOGY: Solitary or scattered in leaf litter of deciduous trees; especially alder, cottonwood and maple, typically in riparian habitats. More rarely in conifer duff or around well-rotted woody debris. Saprobic on leaf litter and duff. Fruiting in spring and fall.
SIMILAR SPECIES: Agaricus augustus has a similarly colored and textured cap, but becomes more amber-colored in age, has distinctly free gills at all stages, a strong almond odor, and dark chocolate brown spores.