Thallus: crustose, usually well developed, continuous, composed of convex areoles, occasionally immersed and indistinct surface: white to pale gray, smooth but not corticate Apothecia: sessile, 0.1-0.5 mm in diam. disc: dark gray to black, strongly convex, epruinose proper exciple: usually excluded, when present (in young apothecia) hyaline, composed of radiating hyphae, outer edge sometimes with olivaceous (K+ violet) pigment epihymenium: dull green and K+ violet hymenium: 25-40 µm tall; paraphyses: numerous, branched and anastomosing, 1-1.5 µm wide, not capitate; hypothecium: hyaline, 30-40 µm thick asci: clavate, 28-36 x 9-12 µm, 8-spored ascospores: hyaline, (1-)3(-4) septate, fusiform, often ±curved, 10-17 x 2.5-3.5 µm Pycnidia: usually present, immersed to emergent, gray to black, 40-100 µm wide conidia: composed of three types: i) macroconidia, curved, 1-3 septate, 12-24 x 1 µm; ii) mesoconidia, simple, 3.5-5 x 1-1.5 µm; and iii) microconidia, simple, 5.5-7.5 x 0.7-0.8 µm Spot tests: K-, C+ red (in section), KC+ red, P- Secondary metabolite: gyrophoric acid. Substrate and ecology: usually on twigs World distribution: apparently widespread in Europe and NE & SW North America, and also known from Tasmania Sonoran distribution: known from two collections from southern California (San Luis Obispo Co. and San Miguel Notes: Micarea nitschkeana is very similar to M. denigra-Island). The microconidia occur in the smallest pycnidia. ta, which has 1-septate ascospores and usually occurs on wood.