Kingdom:   Fungi
Division:    Basidiomycota
Class:        Agaricomycetes
Order:       Agaricales
Family:      Tricholomataceae
Genus:      Leucopaxillus
Species:     L. giganteus
Binomial name: Leucopaxillus giganteus
Synonyms: Agaricus giganteus, Aspropaxillus giganteus, Clitocybe gigantea, Omphalia geotropa var. gigantea, Paxillus giganteus.
Common name: Giant leucopax, Giant clitocybe. Giant funnel.

Leucopaxillus giganteus is an uncommon worldwide species of saprobic fungus with a cap that can reach a diameter of up to 45 cm. The funnel-shaped cap is white/pale cream and has cream gills which run down the stem. The spore print is white. 
The stem is typically 4 to 6cm tall and 2 to 3cm in diameter. It is initially creamy white, turning a buff colour.
It is typically found in late summer to late autumn, growing in groups or rings in grassy pastures, roadside hedges, or woodland edges.
Leucopaxillus giganteus contains a number of bioactive compounds, one of which has displayed antibiotic and anti-tumour properties in laboratory tests.

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Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/