Thallus: crustose, bullate-areolate, to c. 3 cm across, up to 1-2 mm thick centrally, thinner towards periphery; prothallus: white, distinctly fibrous and +radiating, visible at periphery of thallus areoles: +contiguous but mostly discrete, becoming constricted at the base and somewhat lifted off the substrate, but not stipitate, 0.3-1 mm across, convex to occasionally somewhat foveolate or cerebriform, rounded to crenate-lobed and irregular upper surface: dark orange-yellow (to medium orange or brownish orange), turning moderate yellow to light orange-yellow or light olive brown when wet, dull to rather weakly shiny, epruinose, esorediate upper cortex: pale brown, with +unoriented, gelatinized hyphae, c. 25 um thick, often with dead algal cells, interspersed with fine granules soluble in K but insoluble in N; epinecral layer: 15-25 µm thick medulla: loose, cottony, without granular deposits, with 3-4 µm wide hyphae; algal layer: +continuous, c. 100 µm thick; algae: 10-15 µm in diam. lower cortex: present on uplifted parts, similar to and continuous with upper one lower surface: slightly paler than upper, without rhizinal strands Apothecia: lecanorine but often appearing biatorine or lecideoid, numerous, becoming crowded in places, borne laminally to marginally, 1-3 per areole, adnate to sessile, becoming constricted at base, 0.5-1(-2) mm in diam. disc: brownish black, paler and dark-spotted when wet, dull, initially concave but then plane to distinctly convex, finely and lightly white-pruinose margin: concolorous with thallus or becoming dark brown or blackening, 0.1-0.2 mm wide, entire to flexuous or coarsely crenate, raised and persistent for a while or soon becoming excluded, without a parathecial ring amphithecium: present, with an algal layer in center of margin and extending below the hypothecium where it forms an uneven to interrupted layer, with a poorly differentiated medulla without granules or crystals, corticate; cortex: inner part hyaline or pale and with unoriented hyphae c. 3 µm wide and 10 µm long; outer 10-25 µm either pale and inspersed with granules as in thallus cortex or becoming brownish black with radiating hyphae with somewhat enlarged brown-black apical cells, overall 50-75 µm thick, with an epinecral layer 1015 µm thick parathecium: hyaline, poorly differentiated epihymenium: brown-black, K-, N+ red, inspersed with fine granules insoluble in K and N, with thin covering of coarser granules, c. 10 µm thick hymenium: hyaline, 4555 µm tall; paraphyses: simple to forked; +coherent, often clustered together near the tips into groups of 3-5; cells: c. 10 x 1-1.5 µm, the top 1-3 cells shorter and enlarged to 3-4 µm wide, with brown-black to olive-black walls; subhymenium: pale yellow-gray to pale brown, c. 25 µm thick, sometimes with oil droplets; hypothecium: hyaline to pale yellow, 75-100 µm thick centrally, with conglutinate, unoriented hyphae with cells 5-7 µm across and narrow lumina asci: clavate, 35 x 11-17 µm, 8-spored ascospores: hyaline, simple, mostly broadly ellipsoid, (5-)7-10(-12) x 4-6(-7.5) µm, somewhat thick-walled Pycnidia: common in places, immersed, c. 150 µm deep, 100 µm wide; wall: pale brown but dark brown to black around the ostiole; conidiogenous cells: simple to forked; cells: c. 10 x 2-3 µm conidia: formed acrogenously, filiform, straight to curved, 12-15 x 1 µm Spot tests: cortex K+ yellow (appearing more strongly orange-yellow), C-, KC- P-; medulla K-, C-, KC- P+ strongly yellow Secondary metabolites: cortex with atranorin; medulla with alectorialic acid (major) and unknowns. Substrate and ecology: on volcanic rock, with a yellow Acarospora, Lecanora bicincta, and Umbilicaria virginis Sonoran distribution: Arizona, known only from the type locality. Notes: Lecanora subcavicola closely resembles L. cavicola in the apothecia and in the form and color of the thallus, but lacks soralia. Other differences are that in L. subcavicola the medulla does not become lacunose or hollow, and the hyphae are not encrusted with crystals; the apothecial cortex is evenly thickened rather than expanded below, the parathecium is scarcely differentiated, the epihymenium is interspersed with fine granules, the paraphyses lacking oil droplets, and the conidia are somewhat shorter. Lecanora subcavicola is similar to L. pringlei subsp. brandegei but differs in: 1) its thallus being thinner, more crustose (verrucose-areolate), with a whitish prothallus; 2) its surface, mostly dull, pale orange, without olive or black tinges; 3) its upper cortex, thinner; 4) its apothecia pruinose, usually soon convex and immarginate; 5) its proper parathecium, poorly differentiated, not evident from above; 6) its epihymenium having granules, K-; 7) its paraphyses not being constricted at the septa, clustered; and 8) its pycnidial ostiole being black. On some thalli or parts of thalli the apothecia are mostly scattered and concave with distinct thalline margins, on others they are mostly crowded, convex and immarginate.