Squamules: up to 6 mm wide, elongate, adnate and dispersed to adjacent or imbricate, weakly concave to weakly convex upper surface: castaneous brown, shiny, epruinose, smooth or sparingly fissured margin: concolorous with upper side, often slightly down-turned, entire, crenulate or lobed upper cortex: up to 140 µm thick, composed of thick-walled hyphae with angular lumina, containing crystals of lichen substances but no calcium oxalate medulla: not containing crystals lower cortex: of mainly periclinally oriented hyphae, not containing calcium oxalate lower surface: medium brown, K- Apothecia: up to 1.5 mm diam., laminal, immarginate or marginate when young and later immarginate, dark brown to black, epruinose ascospores: ellipsoid, 12-14 x 5-7 µm Pycnidia: laminal, immersed conidia: bacilliform, 5-7 x 1 µm Spot tests: upper cortex K-, C+ red, KC+ red, P-; medulla K-, C-, KC-, P- Secondary metabolites: bourgeanic and gyrophoric acids, and trace of lecanoric acid. Substrate and ecology: on soil and in crevices of rock, in open habitats in the lowlands, up to 980 m alt. in California, at 1250 m on Isla Guadalupe World distribution: west coast of North America north to Washington Sonoran distribution: fairly common in coastal California and Baja California. Notes: The C+ red and KC+ red reactions in the upper cortex are often difficult to observe. The present delimitation conforms with chemical strain I of Timdal (1986); strain II is here treated as P. hyporubescens.