Rhizocarpon geographicum “Map Lichen"
Mount Rainier National Park, WA
August 9, 2013
Robert Niese
Map Lichen is an easily recognizable montane species of crustose lichen that can be found throughout the Pacific Northwest. Look for its characteristic yellow thallus with black apothecia (the black dots surrounded by yellow). Individual lichens are bordered by a thick black line (seen clearly in the center left of this image) which makes them look somewhat like delineated countries on a map (hence the name).
Northwest Naturalist 