Pileus 30-50 x 30-45 mm when still closed, subglobose, ellipsoid or ovoid, expanding to campanulate or almost flat and then up to 90 mm wide, at first beige or pale brown, soon darker, orange- or red-brown and squamulose, especially at centre, the scales often upturned at tips. Lamellae, L = > 50, l = 3-7, first white, then greyish-brown to almost black. Stipe 60-100 x 5-13 mm, white but brown squamulose above clavate, often slightly marginate base.
  Spores 9.8-11.4 x 5.3-6.3 µm (8-9.5 x 4.5-5.5 µm ss. P.D. Orton & Watl.: 33. 1979), Q = 1.55-1.95, av. Q = 1.80, av. L =7.9-9.3 µm, av. B = 4.6-5.9 µm, ellipsoid or ovoid, with rounded base and apex, dark red-brown; germ pore central, 1.1-1.2 µm wide. Basidia 18-32 x 7-9.5 µm, 4-spored, surrounded by 3-6 pseudoparaphyses. Pleurocystidia 100-170 x 20-40 µm, rather narrowly cylindric or slightly utriform. Cheilocystidia 50-100 x 15-30 µm, similar to pleurocystidia. Elements of veil 50-100 x 4-20 µm, somewhat thick-walled in places, branched and slightly diverticulate, hyphoid. Clamp-connections present.

Habitat & distribution

  On stumps of trees, fasciculate. Rare. America, Europe.

Remarks

  Coprinus romagnesianus differs from C. atramentarius in the orange-brown to red-brown colour and the more abundant squamulose veil.