Thallus: crustose, thin, discontinuous or continuous becoming rimose, rarely rimose-areolate, areoles up to 0.4-0.6 mm wide, plane surface: gray to yellowish or reddish brown, dull or smooth; margin: indeterminate; prothallus: absent; vegetative propagules: absent Apothecia: frequent, adnate, mostly dispersed, up to 0.35-0.5 mm in diam. disc: dark brown (particularly when moist) to black, plane, frequently becoming convex thalline margin: concolorous with thallus, c. 0.05 mm wide, entire, becoming excluded, or biatorine and concolorous with disc; excipular ring: absent or confluent thalline exciple: 25-50(-60) µm wide laterally when present; cortex: 5-10(-15) µm wide; epinecral layer: sometimes present, c. 5 µm wide; cortical cells: up to (3.5-)4.5-6 µm wide, pigmented or not; algal cells: up to 9-15 µm in diam.; thalline exciple: sometimes expanded to 30-60 µm below; cortex: then 5-30 µm thick, intricate proper exciple: 5-10(-15) µm wide laterally, expanding to 20-35 µm at periphery, 30-60 µm wide if margin biatorine, outer part pigmented red-brown hymenium: 65-90 µm tall; paraphyses: 2-2.5 µm wide, conglutinate, with apices up to 3.5-4.5 µm wide, lightly pigmented, immersed in a dispersed pigment forming a light or dark red-brown epihymenium; hypothecium: hyaline, 30-80 µm thick asci: clavate, 40-70 x 15-20 µm, 8-spored ascospores: brown, 1-septate, ellipsoid, type A development, Physconia-type, (15-)17.5-18(-21) x (7.5-)8.5-9(-10) µm, some with apical wall thickening at first (Physcia-like), lumina with relatively persistent, narrow, elongate isthmus during development; torus: present; walls: lightly ornamented or not (Fig. 63) Pycnidia: globular, red-brown; conidiophores: type I conidia: bacilliform, 3-4 x c. 1 µm Spot tests: all negative Secondary metabolites: zeorin present. Substrate and ecology: on bark and wood (Alnus and Quercus in North America, Acer, Rhododendron, Salix sp., and Sorbus in Europe) World distribution: known from Scandinavia, the European Alps , Siberia, and North America (British Columbia to Arizona) Sonoran distribution: Pima and Coconino Counties, Arizona, in moist habitats at elevations of 1275-2380 m. Notes: Rinodina trevisanii has previously been confused with R. archaea in Europe. It is characterized by a thin, continuous to rimose thallus (rarely rimose-areolate), mostly scattered apothecia with discs frequently becoming convex, the narrow thalline margins often becoming biatorine, and Physconia-type spores with elongate lumina canals during development. In contrast, R. archaea typically possesses a thicker, areolate thallus, apothecia that become contiguous, then angular by compression, persistently plane discs and prominent, persistently thalline margins, and larger spores. A new species to North America.