Hericium ramosum

Common Name: None.
Description: Fruit body a mass of white, long, multiple branched stems covered with large numbers of very small spines. Whole fungus 10-25 cm across, 10-15 cm high; stems thin, branched, covered on both sides with spines 0.5-1 cm long.
Habitat: on fallen logs of beech and maple. Found throughout North America.
Edible: Yes, and tasty.

Source: Mushrooms of North America by Roger Phillips.