Thallus: fissured to fissured-areolate, with thin to moderately thick verrucae; margins: entire, unzoned upper surface: green-yellow to sulfur-yellow, smooth to tuberculate or rugose-plicate, dull, slightly pruinose; lacking soredia or isidia or superficially sorediate fertile verrucae: concolorous with thallus, lecanorate, numerous, often fused, c. 0.5-1.8 mm in diam. Apothecia: 1 (-2) per verruca; disc: brown to blackish brown, sunken, yellowish pruinose; epithecium: yellow-brown to brown, K+ violet; hypothecium: yellowish to brown asci: cylindrical, 150-300 x 50-70 µm, 2 (-4)-spored ascospores: hyaline, ellipsoid to fusiform or oval, 50-115 x 25-60 µm; spore wall: c. 8-28 µm thick, 1-layered Pycnidia: not seen Spot tests: K+ yellow, C+ orange, KC-, P+yellow to orange, UV+ orange-red Secondary metabolites: stictic and thiophaninic acids (both major), constictic acid, 2-chloro-6-O-methylnorlichexanthone, and 4-chloro-6-O-methylnorlichexanthone (all minor). Substrate and ecology: The species grows on siliceous rocks at the coast and the coastal mountains at 0 -200 m and some specimens were collected at an elevation of up to 750 m World distribution: endemic to western North America Sonoran distribution: coastal southern California and Baja California and at scattered inland locations in southern Arizona and Sonora. Notes: This taxon can easily be recognized by the yellowish thallus, large lecanorate verrucae with pruinose discs, ± 2-spored asci, and the presence of stictic and thiophaninic acids. Some morphotypes of P. tejocotensis may be similar, but this species is distinguishable by poriform apothecia, 4-spored asci, and the presence of depsides instead of stictic acid. Pertusaria flavicunda is generally a uniform species, but some populations differ in producing soralia instead or in addition to apothecia. The sorediate morphotypes do not differ in any other morphological or chemical characters.