Pileus up to 20 x 15 mm when still closed, up to c. 30 mm when expanded, first ellipsoid, cylindric-ellipsoid, grey-brown (Mu. 10 YR 6/3) at centre beneath the whitish to silvery grey veil, paler to margin (Mu. 10 YR 7/3 half-way pileus), expanding to conical, then to convex or applanate, finally plano-concave with revolute margin. Veil in primordiasmooth, mat, pure white, later grey to grey-brown (Mu. 10 YR 7/3), covering entire pileus, soon radially splitting up into hairy to fibrillose, often pointed and adpressed or - especially at centre - recurved flocks, the tips becoming brown on drying. Lamellae, L = c. 45-60, l = 3-7, free, narrow, rather crowded, first white, soon greyish brown to blackish. Stipe 50-100 x 2-6 mm, whitish, somewhat tapering towards apex, up to 9 mm wide at clavate to bulbous base, hollow, hairy flocculose over the whole surface but particularly densely at lower part, becoming glabrous with age. Base sometimes somewhat rooting.
  Spores [100/5/4] 8.4-11.8 x 5.8-7.8 µm, ellipsoid or ovoid, seldom somewhat cylindrical, with rounded base and apex, and central, c. 1.3-1.5 µm wide germ pore, dark red-brown under microscope; Q = 1.25-1.65, av. Q = 1.35-1.55; av. L = 9.0-10.6, av. B =6.1-7.0 µm. Basidia 15-36 x 7-11 µm, 4-spored, surrounded by 3--6 pseudoparaphyses. Pleurocystidia 50-140 x 20-55 µm, subglobose, ellipsoid to oblong, utriform or subcylindrical. Cheilocystidia 35-85 x 15-50 µm, (sub)globose, ellipsoid to oblong. Pileipellis hyphoid. Veil made up of elongate, sausage-like elements, (20)40-250(-450) x 8--40(-50) µm, often inflated, usually constricted at septa; terminal cells cylindrical to almost globose. Clamp-connections present.

Habitat & distribution

  Common. Growing solitary or fasciculate on heaps of mixed dung, rotten straw or vegetable refuse, less frequent on pure dung. Wide-spread all over the world.

Remarks

  The size and shape of the spores are the most significant characters to identify Coprinus cinereus. The spores are relative broad with regard to the length. Rather close species are C. lagopus having spores more elongate, usually up to 13 µm in length with a quotient > 1.6 and usually growing terrestria and C. macrocephalus with larger spores, up to 14 µm inlength and up to 8.5 µm broad.