Squamules: up to 6 mm wide, rounded, adnate and dispersed to adjacent or imbricate, weakly concave to weakly convex upper surface: orange to bright red or rose, dull or shiny, epruinose or partly to entirely pruinose, smooth or sparingly fissured margin: concolorous with upper side or white, straight or slightly up-turned, entire or often weakly crenulate (especially when young) upper cortex: up to 80-120 µm thick, composed of thin-walled hyphae with round lumina, containing crystals of calcium oxalate but no lichen substances medulla: containing crystals of calcium oxalate, sometimes also lichen substances lower cortex: absent or poorly developed lower surface: white to pale brown Apothecia: up to 2 mm diam., marginal, immarginate even when young, black, epruinose or white or yellow pruinose ascospores: ellipsoid, 11-18 x 6-8 µm Pycnidia: laminal, immersed conidia: bacilliform, 6-7 x 1 µm Spot tests: upper cortex and medulla K-, C-, KC-, P- Secondary metabolites: none detected or rarely traces of norstictic acid. Substrate and ecology: on more or less calciferous soil and crevices of rock in open habitats, from deserts to conifer forests, up to 1860 m World distribution: Africa, Asia, Australia, Europe and North and South America Sonoran distribution: common in Arizona, California, Baja California, Baja California Sur and Sonora. Notes: Specimens containing hyposalazinic and hypostictic acids occur in Colorado and Utah (plus Europe); these tend to have more rose colored squamules. In the Arctic, specimens with a high concentration of norstictic acid are common. There are other chemical strains in Australia and South Africa.