My neighbor Jack, showed me this mushroom growing on one of his trees. The mushroom book is 6 inches by 9 inches, so you can get an idea of the size of this specimen.
A closer look at the spines on the edges reveals tapering structures each of which ends in a point. All the points curve in the same direction.
This is Hericium erinaceus, which has many common names including Lion’s Mane, Satyr’s Beard, Monkey’s Head, Bear’s Head, Bearded Tooth, and Pom-Pom Blanc. It is edible and is thought to have several medicinal properties. It grows on dead or dying wood, often at a wound on a tree. This species has a very wide range across North America, Europe and Asia. The genus name Hericium means “hedgehog” in Latin and references the spiny surface.
Lion’s Mane mushrooms are prized edibles and have long been used in Chinese Traditional Medicine. A summary of the purported medicinal properties of this species is given in this post.