Favolus alveolaris, also known as Polyporus alveolaris

Common Name: None.
Description: Fruit body annual; often with a short lateral stem. Cap 1-9 cm across, semicircular to ovoid; pallid reddish yellow; scaly at first. Stem lateral, short or absent, about 10 mm long; colored like the pores.
Habitat: on dead wood o deciduous trees. Found throughout most of North America.
Edible: but tough.

Source: Mushrooms of North America by Roger Phillips.