Pileus up to 30 x 18 mm when still closed, up to c. 40 mm when expanded, first ellipsoid or cylindric-ellipsoid, pale grey-brown to dark grey-brown at centre beneath the whitish to silvery grey veil, paler to margin, expanding to conical, then to convex or applanate, finally plano-concave with revolute margin. Veil pale grey, silvery grey or grey-brown, covering entire pileus, splitting up into hairy to fibrillose, often pointed and adpressed or recurved flocks, the tips becoming brown on drying. Lamellae, L = c. 60, l = 3-7, free, narrow, rather crowded, first white, soon greyish brown to blackish. Stipe 50-150 x 2-6 mm, whitish, somewhat tapering towards apex, up to 8 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 [100/5/5] 12.2-16.8 x 8.2-9.8 µm, ellipsoid or ovoid, seldom somewhat cylindrical, with rounded base and apex, and central, c. 2 µm wide germ pore, dark red-brown under microscope; Q = 1.45-1.80, av. Q = 1.30-1.65; av. L = 13.0-14.9, av. B = 8.2-9.3 µm. Basidia 16-36 x 9-11 µm, 4-spored, surrounded by 3--6 pseudoparaphyses. Pleuro- cystidia 70-150 x 20-60 µm, utriform, ellipsoid, oblong or subcylindrical. Cheilocystidia 50-120 x 20-50 µm, utriform, ellipsoid or oblong. Pileipellis hyphoid. Veil made up of elongate, sausage-like elements, 40-180 x 10--35 µm, often inflated, usually constricted at septa; terminal cells oblong or fusiform. Clamp-connections present.

Habitat & distribution

  Growing solitary or fasciculate on mixed dung, rotten hay or vegetable refuse, less frequent on pure dung. Wide-spread but rare.

Remarks

  Coprinus macrocephalus is close to Coprinus lagopus but differs in habitat on dung or mixed dung and rotten hay and the broader spores.