Global occurrence:  Eurasia – Europe | Americas – North America (incl Mexico) | Arctic.  Substrate: rock – siliceous, siliciferous, acidic.  Life habit: lichenized (mutualistic with algal photobionts).  Thallus: peltate, umbilicate | foliose (foliaceous), leaf-like; [th] upper surface: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | grey(ish) brown; [th upper surface]: epruinose | pruinose; [th upper surface] pruina: scarce, sparse, fine; [th marginal and upper surface] specific structures: absent; [th] lower surface: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | black(ish) brown; [th lower surface] specific structures: absent; [th] medulla amyloidity: absent.  Ascomata: absent | present; ascoma: perithecial, perithecioid – hymenial; [ascm] paraphyses/-oids: absent.  Asci: fissitunicate – verrucarialean; [asc] tholus: thickened; [asc] tholus amyloidity (iodine reaction): absent.  Ascospores: (median) 8.0; [asp] length [µm]: (min) 10.0 (low) 14.0 (high) 20.0 (max) 25.0; [asp] width [µm]: (min) 5.0 (low) 6.5 (high) 9.0 (max) 10.0; [asp] septa: absent – spore lumen unilocular, monolocular; [asp] pigmentation: hyaline, colourless; [asp] perispore, epispore: not apparent.  Secondary metabolites: absent.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.