Thallus: continuous to rimose, areolated with the margins of the areoles often upturned, not immersed in the substrate upper surface: pale sand-colored brown photobiont: a trentepohlioid alga Perithecia: hemispherical, black, immersed in the thallus, 0.4-0.8 mm diam. ascomatal wall: black, continuous below the hamathecium hamathecium: branched pseudoparaphyses, anastomosing above the asci; filaments: c. 1 micro meters wide, not inspersed with oil droplets asci: cylindrical, c. 120 x 12 µm, with 8, uniseriately arranged ascospores, tip with a conspicuous tholus ascospores: hyaline, broadly ellipsoid, 1-septate with a median euseptum, 14-18 x 7-9 micro meters; walls: ornamented with tiny warts, without a gelatinous sheath Pycnidia: frequent to numerous, 0.14-0.20 mm diam. conidia: ellipsoid to narrowly ellipsoid, simple, hyaline Spot tests: all negative, UV negative Secondary metabolites: none detected. Substrate and ecology: on calcareous, disintegrating, sandstone and shale World distribution: mostly temperate in the Northern Hemisphere Sonoran distribution: only known from the Channel Islands in California. Notes: The related Acrocordia cavata (Ach.) R. C. Harris, that occurs on bark, has been erroneously reported from the area, as Arthopyrenia sphaeroides (Wallr.) Zahlbr.