Arctoparmelia separata (aka “Xanthoparmelia separata” or “Rippled Ring Lichen”)
Range: Arctic & boreal south to northern British Columbia & Sask
Description: Lower surface gray to black or purplish black.
Lookalikes: Very similar to the much commoner Arctoparmelia Centrifuga, but the lower surface is a dull mouse-gray, at least in the center of the thallus & sometimes out to the edge. (The more appressed the thallus, the darker the undersurface). It tends to be thicker & stiffer than Arctoparmelia centrifuga.