A rock tripe, #Umbilicaria species. I've also seen these in the #Catskills.
#FungiFriday
https://www.inaturalist.org/observations/143509007
Rock Tripes from Newcomb, New York, United States on September 12, 2014 at 11:19 AM by Chris Kreussling (Flatbush Gardener). NOID fungus (Fungi), Adirondack Interpretive Center, Newcomb, Essex County, New York, 2014-09-12
Flatbush Gardener 🌈