Thallus: crustose, forming delimited suborbicular to irregular patches, effigurate with incised margins, center of thallus rimose-areolate to areolate, up to c. 0.5(-0.6) mm thick; prothallus: conspicuous, mostly visible along the rim, pale brown to dark brown, grayish at inner part areoles: angular to +round, plane to mostly verrucose to sometimes papillae-like, sometimes effuse and irregular or divided into individual scattered warts mainly at the rim, contiguous or sometimes scattered, sometimes inner areoles of the thallus incised, 0.3-2 mm wide surface: white, pale gray ,: green, gray-green to brownish green, with brown edges, becoming dark green and translucent when wet, often slightly shiny, epruinose cortex: mostly developed, paraplectenchymatous, up to 70 µm thick, with coherent cells with lumina 2-6 µm wide, sometimes containing a few scattered algae, brown pigmented in spots, sometimes partly intergrading into an epinecral layer up to 25 µm thick medulla: indiscernible, sometimes visible as a discontinuous tissue; algal layer: continuous, 100-200 µm thick, sometimes weakly paraplectenchymatous or prosoplectenchymatous; algal cells: 8-12 µm in diam. Apothecia: broadly to narrowly sessile, +round to irregular, sometimes clustered in small groups, rarely crowded and deformed, 0.2-1.5 mm in diam. disc: pale to moderately orange-brown, brown to dark-brown, unchanged when wet, plane to moderately convex, rarely slightly white-pruinose margin: thalline, gray to pale brown, always present and often well developed, up to 0.15 mm wide, in young apothecia almost swollen, later somewhat receding, often incompletely fissured amphithecium: with an algal-rich medulla and algal-free cortical zone particularly well developed towards the base of the apothecia, sometimes transformed into an epinecral layer, up to 0.15 µm thick, algal layer: continuous, up to c. 100 µm thick parathecium: usually present, narrow, hardly visible from above, concolored with the disc, up to 40(-50) µm wide toward the outer edge, paraplectenchymatous, often reddish brown externally, with thin-walled, somewhat conglutinated cells epihymenium: pale orange, red-brown to dark brown, spotted, the pigment often shows especially around the coherent paraphyses tips and extends deep into the hymenium; a gelatinous matrix richly present, no epipsamma present hymenium: hyaline below, 60-90 µm tall, rarely slightly inspersed with oil droplets at base; paraphyses mostly simple, rarely sparingly branched, 2-3 µm wide below, hardly or slightly swollen towards apices but at least some usually strongly swollen to 5 µm wide, with the apical cell distinct, coherent due to gelatinous matrix; hypothecium: hyaline, with intricate hyphae, below somewhat conglutinated, up to c. 100 µm thick in the center asci: clavate, 40-60 x 10-17 µm, Bacidia-type, 8-spored ascospores: hyaline, (0-)1-septate, straight, not constricted, oblong-ellipsoid, 12-18 x 4-5 µm, thin-walled Pycnidia: numerous, laminal, immersed, c. 200 µm in diam., hyaline below, pale red brown around the ostiole; ostiole: irregular, c. 150 µm; conidiogenous cells: elongate, branched at base, 8-15 x 2-2.5 µm conidia: relative long, filiform, slightly to strong curved, 18-27 x 0.8 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on acidic rocks as well as artificial substrates (old walls) associated with Caloplaca sp., Dirina catalinariae f. sorediata, Thelomma mammosum, Niebla sp. and Verrucaria sp. in coastal and maritime habitats World distribution: western North America from central to southern California Sonoran distribution: southern California including the Channel Islands, apparently rather common in somewhat disturbed maritime areas and in churchyards with old walls. Notes: Lecania pacifica is characterized by its regularly rimose-areolate thallus with minute placodioid lobes at the edge on its dark brown prothallus and by its relative big apothecia. Some morphs are easily confusable with Lecania inundata, a species known from the Sonoran area and which can occur in the same habitats. But the latter species never has an effigurate thallus, and also differs in having a darker and more distinctly brown thallus with a phenocortex, and discs, that become translucent when wet. Lecania pacifica is similar in some ways to forms of L. fructigena, and sometimes it is difficult to distinguish them, especially if these species are not well developed. The latter species differs in that its discs are in general darker and become paler, browner and dark spotted when wet, its apothecia are smaller, its hymenium is somewhat shorter, and its thallus subunits are usually at least partly constricted at the base. Lecania pacifica might also be confused with forms of L. brunonis, that differs in usually having a darker and browner, verrucose-areolate to subsquamulose thallus, discs turning paler, redder and dark-spotted when wet, amphithecium +soon excluded, and more broadly ellipsoid ascospores. Lecania pacifica can have weakly pruinose apothecia when growing on man-made substrates, that react weakly HCl+. The name L. angelensis has been used by Zahlbruckner for this species that was then known only from Los Angeles Co. However now, many specimens from other areas are known, and we propose a more appropriate name for a species, that is widely distributed along the Pacific coast. The type collection of L. pacifica is infected by the non-lichenized fungus Toninia talparum.