Peltigera - Lichen - Peltigera leucophlebia

I found these at the base of several oak trees.

They are lichen, peltigera species.

Upper and undersides of the lichen. 

Peltigera is a genus of approximately 91 species of lichenized fungi in the family Peltigeraceae. Commonly known as the dog lichen, lichens of Peltigera are often terricolous (growing on soil), but can also occur on moss, trees, rocks, and many other substrates in many parts of the world.