Pileus 20-30 x 10-18 mm when still closed, first oblong or obtusely conical, then conical to convex, up to 55 mm when fully expanded, first white, soon more greyish. Veil white, often somewhat yellow-brown in centre, breaking up in patches. Lamellae crowded, free, first white, then greyish, finally blackish. Stipe up to 95 x 5-9 mm, white, base (8-15 mm) more or less marginate bulbous, white silky striate.
  Spores [80,4,2] (6.7-)7.9-10.7(-11.3) x 5.8-9.0(-11.0) x 4.8-6.7 µm, rounded quadrangular with apical, rather truncate papilla, dark red-brown, with central, c. 1.5-1.8 µm wide germ pore; Q = 1.00-1.45, av. Q = 1.10-1.30; av. L = 8.1-9.8, av. B = 6.5-8.5(-8.7) µm. Basidia 17-35 x 10-11 µm, 4-spored, surrounded by 4-7(-8) pseudoparaphyses. Pleurocystidia 50-140 x 15-40 µm, (sub)cylindrical, oblong, ellipsoid or utriform. Cheilocystidia 30-120 x 10-40 µm, (sub)globose, ellipsoid, oblong, (sub)cylindrical or utriform. Elements of veil thin-walled, slightly diverticulate, 2-10(-15) µm wide, slightly incrusted; sometimes some elements are slightly thick-walled and then somewhat yellowish, less than 0.5 µm; excrescences up to c. 5 µm in length. Clamp-connections present.

Habitat & distribution

  Solitary or a few together among leaves of deciduous trees (Fagus) on calcareous soil. Very rare in England and Germany. Not yet known from the Netherlands.

Remarks

  Coprinus episcopalis is a rather large species in the section Alachuani and easy to recognize by the characteristic shape of the spores. The American species Coprinus maysoidisporus (Redhead & Traquair 1981: 381) is rather close but the spores in that species never have an apical papilla (l.c.: 380) and are somewhat smaller. Furthermore, the basidiocarps of C. maysoidisporus are much smaller (4.5-7 mm when still closed). Coprinus spec. Bas 5002 also comes rather close, but its spores are not angled and are smaller, globose with apical papilla.