Agaricus campestris

Cap	Initially convex and then becoming flattened, the surface of the cap is white and finely flaky and the thick cap flesh is white, turning slightly pink on exposure to air. At maturity, the cap diameter is between 4 and 10 cm.
Gills	The gills are narrow and free; initially grey-pink they turn chocolate brown and eventually almost black as the fruit body matures.
Stipe	At 3 to 6 cm tall, the white stipe is shorter in proportion than that of many species in this family. The stem is solid and its diameter is 1.5 to 2 cm. Below the insubstantial membranous double ring, the surface of the stem is flaky.
Spore print	Deep chocolate brown.
Odour/taste	Not distinctive.
Habitat	On dry soil beside footpaths; occasionally it is to be seen pushing up through tarmac or in the gaps between paving slabs.
Season	Late spring to autumn.
Occurrence	Fairly rare.
Similar species	Agaricus campestris, the Field Mushroom, is very similar but with a more substantial single ring; it is usually taller for the same cap diameter.

Agaricus bitorquis