Thallus: crustose, verruculose or verrucose-areolate; prothallus: not visible areoles: verruculose, thick to thin, opaque, ecorticate surface: yellowish white to yellowish gray or yellowish brown, smooth, epruinose, with an indistinct margin, esorediate Apothecia: constricted at the base to subpedicilate, 0.8-2.5 mm in diam., lecanorine disc: brown or orange-brown, plane or concave, epruinose or slightly whitish gray pruinose margin: concolorous with thallus, thick, persistent, prominent, entire or flexuose, smooth, entire or verruculose, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: hyaline or pale yellow, distinct, uniform, gelatinous or interspersed, 45-95 µm thick parathecium: hyaline, lacking crystals epihymenium: hyaline to yellowish brown, with pigment and crystals dissolving in K, with coarse 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, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid to narrowly ellipsoid, (11.5-)12.5-14(-17) x 5.5-7 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), usnic acid (minor), diploicin (minor), gangaleoidin (minor), and unknowns (minor). Substrate and ecology: on bark of deciduous trees and shrubs World distribution: endemic to southwestern North America Sonoran distribution: southern California, Baja California and Baja California Sur. Notes: Lecanora demosthenesii is very distinct and resembles South American species, such as L. rabdota or L. rabdotoides, two other species with large apothecia that are constricted at the base. However, these species differ in anatomical and chemical characters. L. rabdota has larger ascospores (15-25 x 8-12 µm) and lacks depsidones, while L. rabdotoides contains hypoprotocetraric acid and related substances, and has a basally thickened amphithecial cortex, and an amphithecium that contains both large and small crystals. Some morphotypes of the variable L. pacifica are similar to L. demosthenesii, but can be distingished by its broadly ellipsoid ascospores and its chemistry.