Pileus 5-15 x 3-10 mm when still closed, 25-30 mm wide when expanded, ellipsoid or ovoid, then capanulate to cinvex, finally flat, sulcate-striate up to centre, at first rusty tawny, then fulvous, sienna or cinnamon, outer part clay buff. Lamellae, L = 30-50, l = 1-3, free, slightly remote from stipe, white to blackish. Stipe up to 100 x 1-2.5 mm, whitish to pale greyish brown; base somwhat clavate.
  Spores 12.3-17.1 x 8.8-11.3 x 7.5-10 µm, Q = 1.30-1.70, av. Q = 1.50-1.55, av. L = 14.3-15.3 µm, av. B = 9.5-1O µm, more or less ellipsoid, not distinctly lentiform, with eccentric germ pore and rounded base and apex, very dark red-brown. Basidia 20-40 x 9-12 µm, 4-spored, surrounded by 5-7 pseudoparaphyses. Pleurocystidia 55-75 x 20-24 µm, utriform, subcylindric or sublageniform. Cheilocystidia 40-60 x 13-24 µm, utriform, sublageniform, sometimes ellipsoid. Pileipellis smooth, hymeniform, made up of spheropedunculate cells. Clamp-connections present.

Habitat & distribution

  Terrestrial (from type location) but also on dung. Solitary or a few together. Very rare, only known from type location and one found from the Netherlands.

Remarks

  Coprinus megaspermus can be recognised easely by the large, ellipsoid spores with eccentric germ pore and the naked pileus and stipe.