Ustulina deusta

Common Name: None.
Description: Fruit body 4-10 cm wide, sometimes forming sheets up to 50 cm long; forms irregular wavy cushions or thick soft crusts on the substrate; grayish white in the early stages, finally black and very brittle, resembling charred wood.
Habitat: on old dead roots or stumps of deciduous trees, especially beech, maple, or ash. Common. Found widely distributed throughout North America.
Edible: Not edible.

Source: Mushrooms of North America by Roger Phillips.