Cap 3-8 cm broad, oval, becoming conic, finally campanulate in age; grey-brown, dry, with innate silky fibrils; disc darker, usually with small flattened scales; margin striate to corrugated, deliquescing towards the center; flesh thin, pallid.
Gills crowded, free, white, becoming pinkish-grey, blackening in age.
Stipe 6-15 cm long, 1-2 cm thick, white above, greyish-brown below the ring, dry, hollow, equal to sometimes enlarged at the base; veil fibrillose, forming an evanescent, basal annulus.
Spores 7-11 x 4-6 µm, elliptical, smooth, with an apical germ pore. Spore print black.
Solitary to clustered, in grass, often near rotting wood; fruiting from fall to spring, although specimens can be collected any month of the year that moisture is available.
Edible, but not recommended unless alcoholic beverages are avoided for several days before and after ingestion. It contains a compound, coprine, that can cause nausea, facial flushing, and an accelerated heart beat when ingested with alcohol.
Coprinopsis atramentaria is recognized by its smooth to silky, greyish-brown caps, clustered habit, and deliquescing gills. It prefers disturbed habitats and thus is at home in the urban environment where it inhabits dirt parking lots, gardens, and grassy areas. Like its cousin, Coprinellus micaceus, it often fruits near buried wood. Coprinopsis atramentaria can be easily distinguished from Coprinus comatus which has a columnar-shaped, scaly cap, and from C. micaceus which a yellow-brown mica-flecked cap and is a smaller mushroom.