Poronidulans conchifer

Common Name: None.
Description: Fruit body small cups 0.5-2 cm wide; white, zoned grayish on inner surface. The cups first appear on the wood and then develop into shelflike caps 1-5 cm across, semicircular or kidney-shaped, sometimes with the small cups still adhering to them. Upper surface of cap whitish to grayish-white or yellowish, with concentric zones, particularly on the margin; smooth to minutely hairy or wrinkled.
Habitat: on dead elms and probably other deciduous wood. Found in central and eastern North America.
Edible: No.

Source: Mushrooms of North America by Roger Phillips.