Hammered Shield Lichen

The hammered shield lichen, Parmelia sulcata, is a foliose lichen in the family Parmeliaceae that forms roughly circular patches up to ten centimeters across, with a glaucous white to grey upper surface, a black lower surface and broadly lobed edges. It grows on bark, wood and rock across the temperate and cold regions of both hemispheres, and its tolerance of air pollution has made it one of the most widespread lichen species in the world.