Thallus: squamulose squamules: up to 1 mm diam., thick, convex, crenulate or minutely lobed, appressed or at most with free lobe tips upper surface: white to light gray or pale yellowish-brownish, epruinose or pruinose; vegetative diaspores: absent upper cortex: well developed, up to 100 µm thick, stainable layer composed of mainly anticlinally oriented hyphae interspersed with algal remnants (chlor-zinc-iodine!) and crystals which, at least partly, do not dissolve in K, with a thick epinecral layer medulla: I+ faintly blue, containing crystals which, at least partly, do not dissolve in K algal layer: discontinuous, interrupted by conical strands of upper cortex lower cortex: thick, white, poorly defined from medulla lower surface: pale brown to white, rhizines: absent hypothallus: absent Apothecia: up to 1 mm diam., sessile, becoming constricted at the base, plane and marginate when young, becoming convex and immarginate, dark brown, pruinose ascospores: narrowly ellipsoid to shortly bacilliform, 1-septate, hyaline 13-21 x 4-5 µm Pycnidia: immersed conidia: shortly bacilliform, 3-3.5 x c. 1 µm Spot tests: K-, C-, KC-, P+ orange Secondary metabolites: pannarin, zeorin, and undetermined secondary products. Substrate and ecology: on soil and rock in open habitats near the coast, up to 150 m World distribution: southern and central coast of California Sonoran distribution: Channel Islands, southern California, rare. Notes: Solenopsora crenata is characterized by its small, white to light gray, crenulate to minutely lobed squamules. It is morphologically similar to S. carpatica, but that species has more ascending squamules and shorter spores.