Panaeolus fimicola

Panaeolus fimicola, also known as Panaeolus ater is a rare but widespread little brown mushroom which sometimes contains small amounts of the hallucinogen psilocybin.

Description
This is a little brown mushroom that grows on dung and grass and has black spores. The cap is up to 3 cm across, dark grey to black, sometimes reddish, convex to plane. The stem is 8 cm by 15 mm, fragile and hollow.