Thallus: crustose, areolate to subsquamulose, moderately thickened, ±continuous; prothallus: distinct, black, arachnoid, surrounding the thallus and between the areoles (forming a hypothallus) surface: usually olive gray, rarely brownish olive, dull or rarely ±shiny, smooth, epruinose, phenocorticate, esorediate medulla: white, lacking calcium oxalate (H2SO4-) Apothecia: lecideine; (0.1-)0.2-0.4(-0.5) mm in diam., initially immersed, appearing aspicilioid, soon bursting through the thallus surface and becoming adnate to sessile margin: black (or color masked by grayish remains of necrotic thalline material, thalline veil), thin, usually persistent, rarely excluded with age disc: black, epruinose, plane, rarely becoming slightly convex with age proper exciple: narrow, poorly differentiated, aethalea-type, inner excipular hyphae narrow, hyaline, prosoplectenchymatous (textura oblita), often ±reduced, similar in structure and orientation to the paraphyses, transient with the deep reddish brown hypothecium (leptoclinoides-brown, textura intricata), outer excipular hyphae parallel, moderately swollen (textura oblita) strongly carbonized with various amounts of a fuscous brown pigment (cf. elachista-brown and cinereorufa-green, HNO3+ violet) epihymenium: brown, pigmentation continuous with the outer exciple (HNO3+ violet) hymenium: hyaline, not inspersed with oil droplets; paraphyses: simple to moderately branched, apically swollen, with a brown pigment cap (cf. elachista-brown) asci: clavate, Bacidiatype, 8-spored ascospores: soon brown, 1-septate, broadly oblong to ellipsoid, mature spores slightly constricted, with obtuse ends, not curved, (9-)10.5-[11.3]-12.2(-13) x (4-)5.6-[6.2]-6.8(-8) µm (n=100); proper septum: narrow, not thickening during spore ontogeny (Buellia-type); ornamentation: not visible in immature and premature spores, becoming microrugulate in mature spores (best seen in DIC) Pycnidia: rare, globose, unilocular; ontogeny similar to the Umbilicaria-type conidiogenous cells: mostly terminal, rarely also intercalary (cf. conidiophore-type V) conidia: bacilliform to ellipsoid, 2-5 x 1-1.5 µm (n=73) Spot tests: all negative (K-, P-, C-, KC-, CK-) fluorescence: UV- (dark) iodine reaction: medulla non-amyloid Secondary metabolites: none detected. Substrate and ecology: epilithic, on mineral-poor rock substrates such as quartzite and schist in open oak-conifer forest World and Sonoran distribution: currently known only from Santa Cruz Island (California), and from Isla Guadalupe (Baja California), but it possibly also occurs along the coast of southern California. Notes: Buellia ryanii superficially resembles some forms of B. punctata and was therefore identified as that species in the past (Bungartz et al. 2004b). In the Sonoran Region, B. punctata has almost never been found on rock. If pycnidia are present, both species can reliably be distinguished by their conidia. The dull olive epihymenium and outer exciple of B. ryanii always react HNO3+ violet, even though the pigmentation does not superficially look very different from the dull brown, HNO3- epihymenium and exciple of B. punctata. Thalli of B. ryanii are areolate, becoming sub-squamulose and are gray to olive, a color similar to rimose-areolate thalli of B. punctata s.str. Apothecia of B. ryanii burst through the cortex, initially appearing aspicilioid. Buellia tergua is another species with similar, initially aspicilioid apothecia and bacilliform conidia. However, thalli of B. tergua are rimose rather than areolate, and brown instead of gray or olive. The aeruginose, HNO3+ violet pigmentation of the exciple and hymenium is much stronger in B. tergua, which appears deep bluish green in section. Spores of B. tergua become soon ornamented and are distinctly larger (10-15 x 6-9 µm) than in B. ryanii (9-13 x 4-8 µm), and the spores of B. tergua develop ornamentation at a later stage. Conidia are also slightly longer in B. tergua (4-7 µm) compared to B. ryanii (2-5 µm).