Life habit: lichenized Thallus: crustose, areolate, with elongated lobes 0.2-0.5 mm long, 0.1-0.2 mm wide; prothallus: present or absent, white surface: orange, smooth, sorediate; soredia: granular in delimited, marginal, irregular soralia, cortex: cellular, 7-15 µm thick, granules absent, medulla dense, without granules Apothecia: adnate, 0.3-1 mm in diam., lecanorine disc: orange, flat, epruinose margin: persistent, flush; thalline margin present, concolorous with thallus; proper margin visible, concolorous with disc parathecium: consisting of radiating hyphae; exciple below hypothecium amorphous epihymenium: golden, K+ red, H-, 10%N-, cN-, C- hymenium: hyaline, 55-80 µm tall paraphyses: tip cells not swollen, frequently branched; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 11-14 x c. 5.5 µm, isthmus 3-4 µm, spore end wall thin Pycnidia: present, totally immersed, ostiole orange Spot tests: apothecial margin K+ red, H-, 10% N-, cN-, C-; thallus K+ red, H-, 10%N-, cN-, C-; medulla IKI- Secondary metabolites: unidentified anthraquinones. Substrate and ecology: on non-calcareous rocks World distribution: Mexico Sonoran distribution: southern California and Baja California. Notes: Caloplaca pygmaea is characterized by the sorediate areoles that develop into short lobules and by the fairly common apothecia that usually lack a thalline margin. Caloplaca flavogranulosa has low, convex areoles, rarely has marginal lobes, has an obvious yellow prothallus:, paraphyses with unbranched or little branched tips, sorediate apothecial margins, usually has apothecia with a thalline margin, and the areoles are more convex and somewhat larger. Caloplaca stellata also has lobes with terminal soredia but is not areolate in the center, the lobes form a more regular radiating pattern, and it is never sorediate on the lobe surface. Also, C. stellata is an inland species. Caloplaca citrina has sorediate areoles that are not lobed or notched and less frequently has apothecia.