Thallus: crustose, thick, consisting of scattered, convex verrucae at first, later growing into areoles up to 1.2-1.6 mm wide, plane, becoming subumbilicate with free or upturned, lobate margins, lobes sometimes dissected and erect in center surface: ochraceous to brown, shiny or white pruinose; margin: determinate; prothallus: lacking; vegetative propagules: absent Apothecia: scattered, usually single on areoles, innate, becoming adnate, up to 0.7-0.85 mm in diam. disc: black or pruinose, plane becoming convex and sometimes fissured thalline margin: concolorous with thallus, c. 0.1 mm wide, entire and persistent or becoming excluded; excipular ring: absent thalline exciple: 85-200 µm wide laterally when apothecia not innate; cortex: 10-20 µm wide; epinecral layer: 20-30 µm thick (to 70 µm thick on thallus); cortical cells: up to 4.5-8 µm wide, pigmented or not; algal cells: up to 11-26.5 µm in diam. proper exciple: hyaline, 10-15 µm wide laterally, expanding to 15-40 µm at periphery hymenium: 70-110 µm tall; paraphyses: 2-3.5 µm wide, not conglutinate, with apices up to 5.5-6 µm wide, forming a brown epihymenium; hypothecium: hyaline or pale yellow, inspersed, 50110(-180) µm thick, extending as a stipe into the medulla when mature asci: clavate, 55-75 x 20-22 µm, 8-spored ascospores: brown, 1-septate, broadly ellipsoid, type A development, Bicincta-type, (15-)17-18.5(-20.5) x (8-)9.510.5(-12) µm, walls dilated at septum when immature but not more so in K, waisted at septum when overmature; lumina becoming rounded at maturity, pigmented bands around cells often poorly developed; torus: absent; walls: not ornamented (Fig. 63) Pycnidia: not seen Spot tests: all negative Secondary substances: zeorin. Substrate and ecology: on limestone, carbonate rich shales and sandstones, sometimes associated with intermittent water seepage World distribution: southern Europe, particularly the Alps, China and North America (Colorado Plateau center of distribution) Sonoran distribution: Coconino Co., Arizona, at elevations of 15002200 m. Notes: Rinodina castanomela is characterized by its well developed, pale brown, subumbilicate thallus when fully developed (unique in the Sonoran region), and by its Bicincta-type spores. North American material apparently differs from European specimens in lacking oil droplets in the hymenium, although the hypothecium is inspersed.