Life habit: lichenized Thallus: crustose, continuous or rimose-areolate, without elongated lobes; prothallus: absent surface: gray, verruculose, without asexual propagules cortex: cellular, 25-30 µm thick; medulla with granules insoluble in K Apothecia: adnate, 0.3-1.5(-2) mm in diam., lecanorine disc: brown, flat, epruinose margin: persistent, flush; thalline margin present, concolorous with thallus; proper margin visible, concolorous with disc parathecium: elongate to oval cells; exciple below hypothecium amorphous epihymenium: golden to brown, K+ red, H-, 10%N-, cN-, C- hymenium: hyaline, 60-70 µm tall paraphyses: not swollen or 1-2 tip cells slightly swollen, with few branches; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 14-18 x 7-10 µm, isthmus 4-7 µm, spore end wall thin Pycnidia: not observed Spot tests: apothecial margin K-, H-, 10% N-, cN-, C-; thallus K-, H-, 10%N-, cN-, C- Secondary metabolites: unidentified anthraquinones. Substrate and ecology: on bark World distribution: southwestern North America and northern Mexico Sonoran distribution: Baja California Sur, Sonora, and northern Sinaloa. Notes: Caloplaca diphasia has a K+ yellow epithecium, large apothecia and abundant light gray thallus. This looks very much like members of the Lecanora subfusca group but the spores easily separate C. diphasia from Lecanora. Older specimens sometimes develop a slight yellowish tinge to the apothecial margins. The small paraplectenchymatous cells in the upper parathecium and lack of white pruina easily separate this from C. camptidia.