Thallus: crustose, continuous or verruculose to dispersedverrucose; prothallus: thin, white, fibrous areoles: flat or verrucose or verruculose, thin to fairly thick, opaque, ecorticate surface: yellowish white to yellowish gray or pinkish yellow, smooth or rough, epruinose, with an indistinct margin, sorediate soredia: granulose, 25-50 µm in diam, in confluent, white to yellowish white, soralia 0.30.7(-1.2) mm in diam. Apothecia: sessile to sometimes constricted at base, (0.5-)1-2(-3) mm in diam, lecanorine disc: red-brown, plane, epruinose margin: concolorous with thallus, thick to thin, persistent, even or prominent, entire or flexuose, smooth, entire or rarely sorediate, without a parathecial ring amphithecium: present, with numerous algal cells, with small crystals partly soluble in K, corticate; cortex: indistinct to distinct, basally thickened, gelatinous, inspersed, hyaline, 22-35 µm thick laterally, 30-60 µm thick basally parathecium: hyaline, containing crystals insoluble in K epihymenium: red-brown to orange-brown, with pigment not dissolving in K, without crystals hymenium: hyaline, clear; paraphyses: slightly thickened (up to 2.5 µm wide) or not thickened apically, red-brown to orange-brown ; subhymenium: hyaline, 1520 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, broadly ellipsoid, (8.5-)11-15(-19) x (5.5-)6-8.5(-12) 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), and unidentified triterpenoids (major or minor). Substrate and ecology: on vertical, non-calcareous rock faces, often protected and shaded World distribution: Europe and North America Sonoran distribution: Arizona. Notes: Lecanora umbrosa is characterized by a sorediate thallus, small amphithecial crystals, absence of usnic acid, and broadly ellipsoid ascospores. It is similar to L. brodoana, which is readily distinguished by large amphithecial crystals and the presence of usnic acid. It is also similar to the sorediate L. impudens, but its dispersed thallus and its larger, mostly non-sorediate, rather convex apothcia separate it from that species.