Thallus: crustose, continuous or verrucose-areolate, flat or verruculose, thin, opaque, ecorticate; prothallus: not visible, or blackish to bluish brown surface: yellowish white to yellowish gray or yellowish orange to orange-white or whitish gray to gray; smooth or rough, with an indistinct margin, epruinose, esorediate Apothecia: sessile or adnate, lecanorine disc: brown or dark brown to blackish brown, plane, epruinose margin: concolorous with thallus, thin or thick, persistent, even or prominent, not flexuose, smooth, verrucose or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: distinct, inspersed, gelatinised, 16-25 µm wide laterally, 20-45 µm wide basally parathecium: hyaline, lacking crystals; cortex: distinct, hyaline, basally thickened, gelatinous or interspersed, 15-25 µm thick laterally, 25-65 µm thick basally epihymenium: brown to dark brown, with pigment dissolving in K, with crystals dissolving in K hymenium: clear, c. 30 µm tall; tips of paraphyses: not thickened or slightly thickened (up to 3 µm wide), not pigmented; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid or broadly ellipsoid, (9-)9.5-14 x (6-)6.5-8 µm; wall: less than 1 µm thick Pycnidia: not seen Spot tests: K+ yellow, C-, KC-, P- or P+ pale yellow Secondary metabolites: atranorin (major), chloroatranorin (minor), roccellic acid (major). Substrate and ecology: on bark or wood World distribution: restricted to the temperate of the Northern Hemisphere Sonoran distribution: Arizona and southern California. Notes: Our circumscription of L. meridionalis differs slightly from that of Brodo (1984). In the study area all specimens referred to that name lacked gangaleoidin, as in the type from Switzerland. The collections included under that name by Brodo (1984) mainly from eastern North America contain gangaleoidin, but seem to agree with the type and the specimens from Arizona in morphology.