Trichaptum biformis

Common Name: None.
Description: Bracket 1-8 cm across, semicircular, fan-shaped, flat; color variable in concentric zones, ochre to dark brown, white to grayish, brownish to black, violet margins; hairy becoming smooth. No stem.
Habitat: numerous, single, or overlapping caps on dead stumps of trees of deciduous wood, reducing them to sawdust. Very common. Found widely distributed throughout North America.
Edible: No.

Source: Mushrooms of North America by Roger Phillips.