Life habit: lichenicolous or lichenized Thallus: absent (when lichenicolous) or when independent, endolithic, or chasomilithic, sometimes forming a diffuse, ecorticate areolate crust medulla: prosoplectenchyma, laced through host or substrate algal layer: when lichenicolous, absent; when independent, scattered clumps below apothecia or throughout thallus Apothecia: abundant, erupting from host, or independent, crowded or scattered, convex, 0.3-0.6 mm wide, 0.2-0.5 mm thick disc: black, often umbonate, always gyrose true exciple: parathecium: c. 70 µm thick, outer layer black, carbonized, rough outer layer, 30-45 µm thick, inner layer hyaline to orange-brown epihymenium: blackened, c. 20 µm thick hymenium: hyaline, 60-200 µm tall; paraphyses: 1-1.8 µm wide subhymenium: hyaline, c. 20 µm thick hypothecium: pale yellow to brown, especially in lower half, 60-100 µm thick asci: rare, clavate, 50-75 x 15-22 µm, 100+-spored ascospores: hyaline, simple, broadly ellipsoid, 3-5 x (1.9-)2-2.3(-3) µm Pycnidia: not observed Secondary metabolites: none detected. Substrate and ecology: on acidic rocks, independent or lichenicolous on crustose lichens including Acarospora and Lecidea World distribution: Europe, Asia, and North America Sonoran distribution: Arizona and southern California. Notes: Polysporina lapponica is usually collected growing on other lichens. Its apothecia are larger and more convex than those of P. simplex and can only be confused with the slightly larger apothecia of P. cyclocarpa. The spores in Sonoran specimens are regularly 2-2.2 µm wide. Usually in the vicinity of independent apothecia the remnants of a host can be observed. The description is based on Sonoran specimens. The lichenicolous Polysporina taxa need revision.