Thallus: thin, light to darker grey or greenish-brown, areolate, areoles discrete, irregular, rarely becoming contiguous, up to 0.25-0.60 mm wide, becoming raised at the margins (subsquamulose); surface: plane, quickly becoming rugose or granular, matt; margin: indeterminate, lacking prothallus sorediate: soredia developing from areole margins, other soredia developing from break-up of granules to form discrete, plane or somewhat convex soralia, the same color as the thallus or lighter, often pale green, in dark thalli Apothecia: sessile, sparse, more usually absent, up to 0.60-0.70 mm in diam.; disc: persistently plane, dark brown to black; thalline margin: concolorous with thallus, c. 0.10 mm wide, or thalline margin: incompletely formed, then with a prominent proper margin; excipular ring: usually present, confluent thalline exciple: up to 50-70 µm wide laterally; cortex: 5-10 µm wide, cellular; cortical cells: up to 4-5 µm wide, not pigmented; algal cells: up to 11.5-15.5 µm in diam.; thalline exciple: 50-110 µm below; cortex: to (10-)40-80 µm, intricate proper exciple: hyaline, c. 10 µm wide laterally, up to 25-35 µm above, or 40-60 µm laterally, 70-90 µm below when thalline margin absent, then brownish; hymenium: 70-90 µm tall, not inspersed; paraphyses: 2-3 µm wide, not conglutinate, richly branched near apices, with apices up to 3-5 µm wide, lightly pigmented, immersed in dispersed pigment forming a red-brown epihymenium; hypothecium: colorless, 100-120 µm deep; asci: clavate, 50-70 x 17-19 µm, 8-spored ascospores: broadly ellipsoid, brown, 1-septate, type A development, Physcia-type, (14.5-)17.5-19(-22) x (8-)9.5-10.5(-12) µm, lumina becoming irregular, rarely inflating to fill cells (Physconia-type); torus: well developed; walls: not ornamented Pycnidia: immersed, ostioles brown; conidiophores: Type I; conidia: bacilliform, 3.5-5 x c. 1 µm Spot tests: K-, C-, KC- P+ cinnabar Secondary metabolites: pannarin, zeorin, and secalonic acid A. Substrate and ecology: on bark, recorded from Quercus hypoleucoides at 2000 m. World distribution: widely distributed in Europe and scattered in eastern North America, also known from Washington and British Columbia Sonoran distribution: a single record from the Chiricahua Mountains, Arizona. Notes: Rinodina efflorescens could only be confused with R. perreagens in the study area since both species are characterized by the presence of pannarin. However, the species are easily separated by the discrete soralia and Physcia-type spores of R. efflorescens, in comparison to the diffusely sorediate thallus and larger, Pachysporaria-type spores of R. perreagens. The only other sorediate species from the region, R. griseosoralifera, also has discrete sora-The reported specimen is unusual in lacking the pigment, lia but possesses atranorin and Pachysporaria-type spores. secalonic acid A.