Pileus up to 24 x 17 mm when still closed, up to 30 mm when expanded, subglobose to oblong, densely covered with mealy to hairy floccose veil, grey to grey-brown. Lamellae free, white to black. Stipe 30-60 x 1-3 mm, whitish; base somewhat clavate. Smell none or somewhat rotten.
  Spores 11.2-15.3 x 6.7-8.8 µm, Q = 1.30-1.95, av. Q = 1.45-1.75, av. L = 11.8-13.5 µm, av. B = 7.6-8.2 µm, ovoid, seldom ellipsoid, with conical base and rounded apex, dark red-brown; germ pore central, 1.4-1.6 µm wide; episporium weakly developed, smooth, up to 1 µm wide in places. Basidia 20-38 x 8-11 µm, 4-spored, surrounded by 3-6 pseudoparaphyses. Pleurocystidia 70-120 x 30-45 µm, utriform, oblong or subcylindric. Cheilocystidia 70-120 x 30-45 µm, (sub)globose, ellipsoid, oblong, utriform or subcylindric. Pileipellis made up hyphoid elements. Elements of veil up to 80(-120) µm wide, made up of globose, warty cells connected with narrow, diverticulate hyphae. Clamp-connections indistinct, if present sparse.

Habitat & distribution

  Very rare, terrestrial on mosses and grasses; mountainous areas. Known from France, Great Britain, Greenland, Norway and Switzerland .

Remarks

  Coprinus martinii is a species from Alpine areas and have rather broad, 7-8,5 µm wide spores. No other species with a smooth episporium and 4-spored basidia have spores broader than 7 µm.