Cap 5-12 cm broad, convex, expanding to nearly plane, often with a low umbo; margin inrolled, wavy, becoming decurved to nearly plane, frequently striate in age; surface viscid when moist, appressed fibrillose, brown to reddish-brown, darkest at the disc, slightly lighter at the margin; flesh thick, firm, pallid, unchanging; odor and taste farinaceous.
Gills adnexed, notched to arcuate, close, moderately broad, cream-colored, becoming pale-buff, the edges often developing brownish discolorations.
Stipe 3-6 cm tall, 1-3.5 cm thick, stuffed to hollow at maturity, variable in shape: equal, narrowed to enlarged at the base, sometimes appearing clavate; surface pruinose or ridged from gill edges at the apex, cream-colored, elsewhere covered with appressed fibrils, buff-brown, discoloring darker brown from handling or in age; veil absent.
Spores 4.5-6 x 3-3.5 µm, elliptical, smooth, thin-walled, nonamyloid; spore print white.
Scattered to gregarious under pines, especially Monterey pine (Pinus radiata) and Bishop pine (Pinus muricatum); fruiting from early to mid-winter.
For many years this Tricholoma was known as T. pessundatum, a European species. Kris Shanks has shown, however, that our local material has larger spores and a pileipellis that differs microscopically, thus worthy of species distinction. Tricholoma muricatum, is characterized by a brown to dark reddish-brown, viscid cap, the margin often striate at maturity, a strong, farinaceous odor, and gills that become mottled brown, especially the edges. It is most likely to be confused with Tricholoma fracticum, another dark reddish-brown, viscid species, but the latter forms a conspicuous dark annular line on the stipe, seldom has a striate margin, and lacks a strong farinacous odor. Another pine-dweller common in our area is Tricholoma imbricatum. It is similarly colored but can be distinguished by a dry, not visicd, fibrillose cap and usually mild odor.