Thallus: determinate, rimose to areolate, thin to moderately thick, with thin, acute fissures, several centimeters across, partly bordered by a dark brown prothallus areoles: angular, plane (sterile) or convex (fertile areoles), 0.15-0.30 mm wide when sterile, c. 0.5 mm wide when fertile surface: brown, dull, even anatomy: upper cortex not discernible, algal layer: c. 100 µm thick, with algal cells 6-10 µm in diam., mycobiont portion paraplectenchymatous with cells 5-7 µm in diam.; alga-free medulla: hardly developed in sterile areoles, but light brown medullary tissue may be found around the perithecia Perithecia: immersed in raised portions of larger areoles, laterally ±covered by thin thallus tissue with the apices free and black; exciple: subglobose, 0.2-0.3 mm wide, c. 15 µm thick, pale to dark brown; involucrellum: hemispherical, extending down to base-level of the perithecium, at base 350-500 µm broad, separated in a rather thin (15-40 µm) black outer layer, that arches away from the exciple and slightly spreads towards the base, and an internal part, which is paler brownish, of "Zellnetztyp", up to 100-150 µm broad at the base; periphyses 25-35 µm long, simple asci: clavate, 75-85 x 22-27 µm, 8-spored ascospores: hyaline, simple, ellipsoid to oblong ellipsoid, 24-30 x 9-14 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on siliceous rocks World distribution: Italy and southwestern North America Sonoran distribution: one record from granite in the Pinaleno Mountains in Arizona and one from the Santa Monica Mts. in California. Notes: No type material could be located, but the Sonoran record is in perfect accordance with the description. The construction of the involucrellum (an arching black outer layer, inner portion paler) is diagnostic and makes the species easily identifiable. The pale inner tissue is not prosoplectenchymatous in the strict sense; Servit himself describes the fungal cells as "4-8 µm altis, 4-6 µm latis".