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 0.3 mm thick upper surface: white; creamy or grayish, smooth, slightly farinose upper cortex: lacking but with an epinecral layer with some scattered, hyaline hyphae medulla: white, cretaceous lower cortex: absent prothallus: often present, thin, smooth, black Ascomata: perithecioid, up to 0.3 mm diam., immersed, rounded, oval or elongate, usually numerous, scattered or often in groups or dispersed in flexuose or radiating lines, not aggregated into stroma-like structures; thalline margin: undifferentiated; disc: plane, black, with whitish pruina; proper exciple: up to 15 µm thick, brown above, pale below; hypothecium: pale brown, fusing with medulla; hymenium: 100-150 µm thick, I+ blue, K/I+ pale blue asci: cylindrical, 70-95 x 15-19µm, 8-spored ascospores: oblong-ovoidal to oblong-fusiform, dark brown, (17-) 19-26 x 5-7 µm, 4-6 (-7) septate, constricted at each septum, with thick gelatinous sheath Pycnidia: not seen Spot tests: thallus and medulla K- or K+ yellowish, C-, KC-, P+ yellow (orange) Secondary metabolites: psoromic acid (major) and 2'-O-demethylpsoromic acid (minor). Substrate and ecology: on rocks in coastal habitats World distribution: SW North America, western Europe and the Carribean Sonoran distribution: Baja California. Notes: Specimens from Baja California have slightly fewer septa than European specimens, but no other differences have been found.