Kingdom:     Fungi
Division:     Basidiomycota
Class:     Agaricomycetes
Order:     Agaricales
Family:     Tricholomataceae
Genus:     Clitocybe
Species:     C. nebularis
Binomial name: Clitocybe nebularis
Synonyms: Leucopaxillus giganteus, Agaricus nebularis, Gymnopus nebularis, Omphalia nebularis, Lepista nebularis
Common names: Clouded agaric, Cloud funnel, cloudy funnel cap

Clitocybe nebularis is a gilled introduced fungus which appears in groups under exotic and native trees. It appears from late summer to late autumn.
The cap of the mushroom is 5–25 cm in diameter, convex with an incurved margin, becoming plane to depressed in shape. Cap colours are generally greyish to light brownish-grey, and often covered in a whitish bloom when young. The surface of the cap is usually dry to moist, and radially fibrillose. The stem is stout, swollen towards the base, becomes hollow with age, and is easily broken. It is usually somewhat lighter than the cap. The flesh is white and very thick. It has a foul-smelling odour, which has been described as slightly farinaceous to rancid. (Wikipedia)

This rare species is host to the parasitic gilled mushroom Volvariella surrecta, which is found on older specimens.
See http://www.terrain.net.nz/friends-of-te-henui-group/fungi-te-henui/volvariella-surrecta-piggyback-rosegill.html

This large 210 mm cap mushroom was growing in dense shade under a large avocado tree in rich leaf and decaying fruit matter.Clitocybe nebularis Clouded agaric 2.jpg

Clitocybe nebularis Clouded agaric 3.jpg Clitocybe nebularis Clouded agaric.jpg

Clitocybe nebularis Clouded agaric 4.jpg

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