Thallus: crustose, verruculose or leprose; prothallus: whitish gray areoles: flat or verruculose, thin, ecorticate surface: yellowish green to yellowish gray, rough to leprose, epruinose, with an indistinct margin, sorediate soredia: granulose, 20-35 µm in diam., in diffuse yellowish gray soralia Apothecia: sessile, 0.4-1.2 mm in diam., leca disc: orange-brown or yellowish brown, plane to convex, epruinose margin: concolorous with thallus, thin or thick, persistent, even, not flexuose, smooth, verrucose or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: pale yellow to hyaline, distinct, basally slightly thickened, interspersed, (9-)1116 µm thick laterally, (11-)12-22(-25) µm thick basally parathecium: hyaline, containing crystals insoluble in K epihymenium: yellow-brown to orange-brown, with pigment dissolving in K, with crystals dissolving in K hymenium: hyaline, clear; paraphyses: slightly thickened (up to 3 µm wide) apically, not pigmented; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline to pale yellow, darker yellow to orange in K, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid to broadly ellipsoid, (12-)14.5-16(-17.5) x 5.5-8.5 µm; wall: less than 1 µm thick Pycnidia: not seen Spot test: thallus and apothecial margin K+ yellow, C+ orange, KC+ orange, P+ pale orange Secondary metabolites: containing arthothelin (major), atranorin (major), chloroatranorin (minor), 2,5-dichloro-4-O-demethylplanaic acid (minor or absent), and 6-O-methylarthothelin (major or minor). Substrate and ecology: on bark of conifers at high elevations World distribution: at high elevations of Central America, the Caribbean and SW North America Sonoran distribution: Sinaloa. Notes: Lecanora guderleyii has been treated as "sp. 4" by Guderley (1999). It is characterized by a thin, verrucose to leprose thallus and the orange- to yellow-brown apothecial disc with verrucose margins, and the chemistry. It may be confused with L. arthothelinella or L. pseudachroa, but differs from these in having a leprose thallus and a different chemistry.