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 rimose or verrucose, sometimes bullate, up to 0.6 mm thick upper surface: white to geenish, smooth to slightly verrulose upper cortex: up to 40 µm thick, composed of interwoven hyphae with hyaline tips medulla: white, cretaceous lower cortex: absent prothallus: often present, thin, smooth, black Ascomata: lirellate to dendroid, immersed, usually aggregated into rounded or elongate, slightly elevated stroma-like structures, usually with many ascomata surrounded by a thin, white rim; disc: plane, narrow, slit-like, black, with whitish pruina; proper exciple: up to 15 µm thick, dark brown; hypothecium: dark brown, extending to the substrate; hymenium: 300-350 µm thick, I+ reddish, K/I+ pale blue asci: 125-160 x 25-30µm, 8-spored ascospores: oblong-fusiform to fusiform, hyaline when young, brown at maturity, 30-40 x 8-12 µm, 6-9 (-10) septate transversely and 1-2 septate logitudinally, constricted at each septum, with thick gelatinous sheath Pycnidia: laminal, subglobose, up to 0.25 mm tall and 0.20 mm wide; walls: colorless or reddish brown at upper part conidia: filiform, curved, 13-20 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 rocks in coastal habitats 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.