Cap 3.5-8.0 cm broad, at first obtuse-conic, becoming convex, expanding to nearly plane, in age the disc sometimes broadly depressed; margin incurved, then decurved to plane, occasionally upturned at maturity, often appendiculate with veil fragments when young; surface at first matted tomentose at the disc, medium-brown to hazel-brown, becoming fibrillose-scaly, especially near the margin, ground color pallid-buff; flesh white, firm, moderately thick, discoloring dingy reddish-brown when exposed; odor and taste mild.
Gills free, close, moderately broad, dingy pinkish-brown when young, chocolate-brown at maturity.
Stipe 4.0-10.0 cm long, 1.0-2.0 cm thick, straight, equal to tapered to a narrowed base, fleshy, but hollow to stuffed at maturity; surface pallid, subtomentose at the apex when young, smooth or with scattered fibrils below, discoloring brownish where handled; flesh white, discoloring like the cap, dingy reddish-brown when cut; veil membranous, thin, lower surface pale-coco-brown with scattered darker patches; upper surface pallid, smooth to striate, becoming dark-brown from maturing spores; veil rupturing irregularly, leaving fragments either on the cap margin or forming a thin, dark-brown, pendulous, superior ring which at maturity often becomes tightly appressed to the stipe.
Spores 7-8 x 5-6 µm, broadly elliptical, smooth, thick-walled, hilar appendage conspicuous; spore print blackish-brown.
Scattered to clustered under conifers; fruiting from late fall to mid-winter.
Edible and excellent, but often infested with fly larva.
Agaricus fuscovelatus is distinguished by a somewhat conic (when young), brown squamose cap, reddish-staining flesh, and a thin coco-colored veil, which forms a pendulous ring that soon collapses on to the stipe. Several other red-staining, brown-capped Agaricus species occur under conifers in our area. They include Agaricus fusco-fibrillosus which has an innately fibrillose to squamulose cap, usually tinged rufescent, thick, whitish veil with a brown margin, scaly brownish rings usually near the stipe base, and is associated with Monterey cypress (Cupressus macrocarpa). Agaricus pattersonae is a larger, more robust, fibrillose-scaly mushroom, also with a thick veil, a persistent, (not collapsing) annulus, and like A. fusco-fibrillosus sometimes has encircling scaly rings at the base and is associated with Monterey cypress. Agaricus arorae, an inhabitant of mixed hardwood/conifer woods, has a fibrillose to finely scaled cap, a whitish veil and is our only red-staining species that yellows in KOH.