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DescriptionLife habit: lichenized; Thallus: foliose, ± closely adpressed, to 8 cm across, broadly lobate; lobes: 0.5-10 mm wide; cilia present or absent; upper surface: pale yellow to pale yellow-green, rugose and subplicate, continuous, without pseudocyphellae, maculae, soredia or pustulae; isidia: present or absent; upper cortex: paraplectenchymatous, 15-25 µm thick, composed of c. 3 cell layers; with non-pored epicortex; medulla: white; medullary hyphae: 3-4 µm thick; cell walls: containing Cetraria-type lichenan (medulla I+ blue); photobiont: primary one a trebouxioid alga, secondary photobiont absent; lower cortex: paraplectenchymatous, 15-20 µm thick, composed of 2-3 layers of somewhat brownish cells; lower surface: usually light tan or pale brown (to olive-black), with sparse to abundant simple rhizines to the margins; Ascomata: apothecial, frequent, with prominent thalline exciple, laminal or marginal, sessile, ± circular, up to 13 mm across; disc: brown, non-perforate; exciple: hyaline or grayish, 2-layered; upper layer: 10-30 µm thick, composed of periclinally arranged hyphae; lower layer: 35-50 µm thick, paraplectenchyamtous; hymenium: (including ascogenous layer) 50-60 µm high, uppermost part brown or ochraceous-yellowish; paraphyses: straight, somewhat branched, not (or scarcely) anastomosing; hypothecium: hyaline; asci: narrowly to rather broadly clavate, 45-60 µm high, Lecanora-type; axial body 2-5 µm wide, 8-spored; ascospores: ± uniseriate, simple, globose or subglobose, 4-6 µm diam.; wall: hyaline, smooth, without distinctly developed endospore thickening, not amyloid; Conidiomata: pycnidial, laminal or marginal, emergent, often abundant, black, conspicuous, to 0.2 mm across; conidia: usually bifusiform or occasionally bacilliform, citriform or sublageniform, 5-7 (-9) x c. 1 µm; Secondary metabolites: upper cortex with usnic acid, medulla with aliphatic acids; Geography: montane coniferous forests in western North America; Substrate: on bark or wood.; Notes: It was initially segregated as a monotypic genus from Parmelia, and later two additional species were transferred from Cetraria and Tuckermannopsis. It is characterized by its yellow-green upper cortex (usnic acid), absence of pseudocyphellae, presence of caperatic acid in the medulla and globose ascospores. It differs from Flavoparmelia in having a paraplectenchymatous upper cortex, non-pored epicortex, a medulla lacking depsides and depsidones and with Cetraria-type lichenan (not isolichenan) in the cell walls, and much smaller and ± globose (rather than large and ellipsoid) ascospores.