Thallus: usually flaccid; cortex: thin (3-7%) dull to ±shiny; medulla: lax, rarely dense.; Substrate and ecology: inland on bark (on Pinus spp., Quercus spp., Pseudostsuga menziesii, Abies spp., Picea spp., etc.) or on wood, very rarely on rock, mainly in mixed conifer-oak forests, ponderosa pine forests, spruce-fir communities, oak-juniper woodlands, between 650 and 3600 m; World distribution: probably cosmopolitan on every continent; Sonoran distribution: a frequent inland taxon in the mountains of Arizona, the Sierra Madre Occidental of Chihuahua, and northern Baja California, rarely in southern California and Baja California (Isla Cedros) near the ocean at low altitudes.