Thallus: crustose, stratified, determinate to indeterminate, thick, composed of rounded, convex, sometimes slightly placodioid cushions, 0.5-2 cm in diam. which may become confluent in part surface: lemon yellow, composed of a mass of fine soredia, (19-)25-42(-63) µm in diam. medulla: distinct, yellow in upper part, almost white in lower part Apothecia: not known in Sonoran material, elsewhere with a constricted base, 0.2-1 mm in diam. disc: brownish orange, flat to convex, yellowish pruinose exciple: poorly developed, composed of anastomosing hyphae epihymenium: yellow, composed of a reticulate layer of richly branched paraphysoids hymenium: colorless or pale yellow, 60-70 µm tall; paraphysoids: c. 1 µm wide, intertwined, branched; hypothecium: hyaline, fusing into the medulla, hard and opaque asci: clavate, 8-spored ascospores: hyaline, 3-septate, obovate, straight, 11-15 x 3 µm Spot tests: K+ orange, C-, KC-, P+ orange; UV+ dull dark orange Secondary metabolites: calycin and diffractaic acid. Substrate and ecology: mainly on bark, also wood and rock in shaded and dry microhabitats, possibly also in places subjected to direct sun and rain World distribution: western South America (Chile to Peru) and western North America Sonoran distribution: strictly coastal (often on islands) from northwestern Mexico (Baja California) to southern California (Santa Barbara Co.), sea-level to 400 m. Note: Chrysothrix granulosa is here reported as new to North America. It is apparently a common species along the Pacific coast from Mexico to as far north as British Columbia.