Agaricus macrocarpus

Similar to Horse Mushroom (Agaricus arvensis) but larger, with caps up to 20cm in diameter and with scattered squamules on their surface. The rimmed, bulbous base at the base of the stipe is a useful distinguishing feature (see photos). Probably common and widespread in grassy places at the dges of woodland in parks and other places. There are few records in West Glamorgan where it may have been misidentified as Agaricus arvensis.