Closed pileus ellipsoid or cylindrical ellipsoid, up to 7 mm high and 4 mm wide, completely covered with powdery, white, cream-coloured or pale pinkish ochre veil, at centre of pileus somewhat granular flocculose; expanded pileus up to 10 mm wide, conical or convex, later applanate. Lamellae, L = 18-25, l = 0-3, free or narrowly adnate, c. 1 mm wide, white at first then greyish to black. Stipe up to 35 x 0.5-1 mm, white, somewhat hyaline, minutely floccose, at base clavate, up to 1.5 mm wide, often pale brownish, felty. Smell absent.
  Spores [80,4,3] 5.5-8.5 x 4.8-6.5 x 3.7-4.5 µm, Q = 1.00-1.40, av. Q = 1.10-1.20, av. L = 6.1-7.3, av. B = 5.3-5.5 µm, cordiform, lentiform, red-brown, with central germ pore. Basidia 12-28 x 7-8 µm, 4-spored, surrounded by 3-6 pseudoparaphyses. Pleurocystidia 30-55 x 15-26 µm, vesiculose, utriform or ellipsoid. Cheilocystidia 25-50 x 15-30 µm, subglobose, ellipsoid or utriform. Veil made up of (sub)globose to ellipsoid elements, smooth to granular, up to 50 µm wide. Clamp-connections absent.

Habitat & distribution

  Solitary or in small groups; on compost heaps and horse-dung mixed with soil and wood-chips. Very rare in the Netherlands.

Remarks

  The collection from Germany studied is part of the holotype. Coprinus cardiasporus is very close to C. patouillardii Qu‚l. It differs by having spores that are narrowing towards the germ pore, whereas the spores are rounded angular in C. patouillardii.
  According to Bender (1986), Coprinus cardiasporus has clamped hyphae in the mycelium; we failed to demonstrate them in our study of part of the holotype.