Thallus: crustose, epiphloedal, verruculose-uneven, continuous to rimulose; 0.08-0.2 mm thick, ecorticate surface: dirty ochraceous or pale gray algal layer: with Trentepohlia; algal cells sublobate, 8-15 Ám in diam., partly in filaments Apothecia: crowded, at first immersed then emergent, well elevated above thallus, in warts, 0.5 disc: pale yellow to flesh colored or brown, initially concave then subplane, epruinose margin: ochraceous or pale gray, thick, entire to subcrenulate, with a radiately cracked outer thalline layer exciple: hyaline to pale (concolorous with disc), chondroid-paraplechtenchymatous, in margin 70-90 Ám wide, under the hymenium, c. 30 Ám thick epihymenium: red-brown hymenium: hyaline below, I+ blue then red-brown, c. 200 Ám tall; paraphyses: dense, coherent, simple, straight, tubular, c. 2 Ám wide, without thickened tips asci: cylindrical, 120-150 x 10-12 Ám, with 1 Ám thick walls, I+ blue then red-brown, with uniseriate spores, 8-spored ascospores: hyaline, straight, muriform, 4-12-septate transversely, 5-7-septate longitudinally, fusiform to ellipsoid, (25-)30-38(-40) x 10-13(-18) Ám Spot tests: thallus K-, C-, KC-, P-, I- Secondary metabolites: none detected. Substrate and ecology: on bark of half-dead trees World distribution: western North America (southern to central coast of California) Sonoran distribution: southern California. Notes: In habit Gyalecta herrei resembles superficially a luxuriant form of G. truncigena, and previous reports before 1965 of the latter species from central California may prove eventually to be G. herrei. But anatomically G. her-rei is more similar to G. jenensis in that the ascospores are uniseriate and relatively long, and the paraphyses extending over 1/4 the length of the asci above the asci. It differs from G. jenensis in its taller hymenium, longer spores, and different substrate.