Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: crustose, effuse, continuous to cracked-areolate, sometimes bullate, up to 1.5 mm thick upper surface: creamy white to yellowish or geenish, smooth to slightly verrulose upper cortex: up to 25 µm thick, composed of interwoven hyphae with hyaline tips medulla: white, cretaceous lower cortex: absent prothallus: often present, thin, smooth, black Ascomata: perithecioid and lirellate or apothecioid, usually aggregated into stroma-like structures, 1-3 mm diam., with slightly constricted base, usually with more than 7 ascomata surrounded by a thin slightly elevated thalline margin; lecanoroid ascomata: roundish to ± irregular, 0.4-1.2 mm diam., sessile with a constricted base, smooth, entire or crenulate; disc: plane, black, with whitish pruina; proper exciple: up to 15 µm thick, dark brown; hypothecium: carbonaceous or dark brown, extending to medulla or substrate; hymenium: 140-160 µm thick, I+ reddish, K/I+ pale blue asci: 56-70 x 16-19µm, 8-spored ascospores: ellipsoid to oblong-fusiform, hyaline when young, brown at maturity, 22-30 (-32) x 5-8 (-9) µm, (3-) 5-7 septate, constricted at each septum, with thick gelatinous sheath Pycnidia: laminal, pyriform, up to 0.25 mm tall and 0.18 mm wide; walls: colorless or reddish brown at upper part conidia: filiform, curved, 18-25 x 1 µm Spot tests: thallus and medulla K- or K+ yellowish, C+ reddish, KC-, P- Secondary metabolites: lecanoric acid (major) and erythrin. Substrate and ecology: on bark and rocks World and Sonoran distribution: along the coast (including the Channel Islands) from San Luis Obispo County, California, southwards to Baja California. Notes: At an early stage of development the ascomata resemble those of S. circumscriptum, but they become quite different with age.