Crustose lichen, forming a crust which cannot be removed without damage to the lichen, the substrate, or both. Usually grows on bark, but also found on rocks. The fungal cells invade the outer layer of bark or rock. Lichen body (thallus) grey, usually circular. Spore-bearing structures, called lirellae, are black, usually elongated, often curved, and sometimes forked, giving the impression of a sign written in elvish.

Very common on trees in the Park, but often overlooked.

There are many very similar species of script lichens, but they are tropical or subtropical. This is the only one that apparently gets this far north -- and even makes it to Canada and Ireland!