Agaricus benesii

Agaricus benesii is an agaric mushroom of the genus Agaricus known in English as the mull mushroom. This mushroom can be distinguished by a white cap that bruises pinkish-red when injured, a scaly lower stipe, and a conifer habitat. Similar to Agaricus californicus and A. xanthodermus, the cap discolors brown in age. A distinguishing feature of A. californicus and A. xanthodermus, however, is a thickened annulus at the margin, a phenolic odor, and a yellowing bruise, instead of red. In the case of Agaricus xanthodermus, it occurs quickly, though faintly to not at all in the case of A. californicus. Another similar species, Agaricus bernardii, also stains red and has white flesh, but differentiates on its larger bulk, a sheathing veil, briny odor, and different habitat, namely grass....read more on Wikipedia.