Thallus: crustose, mostly thin but thicker on protected parts of substrate, areolate, areoles up to 0.6-1 mm wide, plane or uneven surface: gray to gray-brown, dull; margin: indeterminate; prothallus: lacking; vegetative propagules: absent Apothecia: often erumpent, then innate, rarely becoming adnate or even sessile, abundant, up to 0.35-0.4 mm in diam., sometimes angular by compression disc: dark brown or black, sometimes concave at first, typically plane, rarely becoming slightly convex thalline margin: typically very thin, lighter than thallus, <0.05-0.1 mm wide, entire and persistent; excipular ring: absent thalline exciple: often not distinguishable from areole margin, 60-70 µm wide laterally; cortex: c. 5 µm wide; epinecral layer: 5-15 µm wide; cortical cells: up to 5-6.5 µm wide, typically lightly pigmented; algal cells: up to 10-16.5 µm in diam.; thalline exciple: c. 80 µm below when apothecia sessile; cortex: not expanded proper exciple: hyaline, c. 10 µm wide laterally, expanding to 10-30 µm at periphery hymenium: 80-100 µm tall; paraphyses: 2-2.5 µm wide, somewhat conglutinate, with apices up to 4-5 µm, lightly to moderately brown pigmented, immersed in dispersed pigment, forming gray-, to orange-brown or reddish brown epihymenium; hypothecium: hyaline, 50-90 µm thick asci: clavate, 50-60 x 16-18 µm, 8-spored ascospores: brown, 1-septate, ellipsoid, type A development, Physcia-type, (13-)16.5-18(-21) x (6.5-)8.5-9.5(-11) µm, lumina angular, sometimes becoming rounded at ends (Physconia-like), finally filling cells when overmature, walls becoming heavily pigmented, pigmented endospore wall sometimes evident at septum, overmature spores often waisted; torus: heavily pigmented at maturity; walls: not or very lightly ornamented Pycnidia: rare, darkly pigmented, immersed in thallus; conidiophores: type I conidia: bacilliform, 3.5-4 x c. 1 µm Spot tests: all negative Secondary substances: none detected. Substrate and ecology: coastal sandstone and calcareous rocks, sometimes on eutrophic bird perches accompanied by R. gennarii above the spray zone World distribution: a North American endemic species with a southwestern oceanic distribution from central California (San Mateo Co.) south to Baja California Sonoran distribution: Channel Islands in southern California and Baja California. Notes: The typical form of R. innata possesses innate apothecia with concave to plane discs, and possesses distinctively thin and light colored margins caused by the broken epinecral layer. Specimens with thicker thalli may have an external morphology similar to R. gennarii when the apothecia become adnate, or rarely, sessile and the discs slightly convex. Anatomically, R. innata is best distinguished by its significantly larger, Physcia-, rather than Dirinaria-type spores that develop a prominent, pigmented torus and by the gray-, orange-, or red-brown epihymenium. Rinodina pacifica may be related to R. innata since it possesses Physcia-type spores in development and both develop endospore wall pigmentation. However, the spores of R. pacifica are significantly larger and its apothecia are always sessile and larger than 0.4 mm in diam. when mature.