Leucocoprinus nigricans
Leucocoprinus nigricans is a species of mushroom producing fungus in the family Agaricaceae. Taxonomy 
It was first described in 1973 by the Czech mycologist Bohumil Ježek who classified it as Leucocoprinus nigricans. This species is currently accepted but appears to have received no attention since and may have simply been forgotten about as the issue of Mykologický sborník - Časopis Českých Houbař it was published in is not easily accessible. Description 
Leucocoprinus nigricans is a small white dapperling mushroom with thin (5mm thick) white flesh. Ježek provided only a brief description of this species in Latin and some of the terms used are antiquated now and do not easily translate. Cap: 2.3cm wide, 1.5cm high and conical when immature expanding to 5.5cm and flattening with age with striations at the edges. The surface is a 'dirty white' colour and has a frosty or fibrous coating when young sometimes with some slight reddening at the top and a sticky surface. Stem: 4.5cm long and 5mm thick with a white, silky and fibrillose surface. Slight striations run vertically up the stem and the base of the stem gradually blackens and may even become black. The white stem ring is located towards the top of the stem but sometimes disappears. Gills: Adnexed, crowded and white. Spore print: White. Spores: Ovoid. 6.5-7.5 x 4-4.5 μm. Smell: Indistinct. Taste: Indistinct. Habitat and distribution 
The specimens studied by Ježek were found growing in groups in Cabo Frio, Brazil in 1971 and the description was published in 1973. Ježek died in Cabo Frio on the first of June 1973 so if he was intending to study this species further, it unfortunately did not happen. GBIF has no recorded observations for this species. Etymology 
The specific epithet nigricans derives from the Latin for 'blackening' and refers to the colouration of the base of the stem. References 

nigricans
Fungi described in 1973