Life habit: lichenized Thallus: crustose, areolate, without elongated lobes; prothallus: absent surface: orange, smooth, without asexual propagules cortex: cellular, thin, granules absent, medulla dense, without granules Apothecia: adnate, 0.3-1 mm in diam., lecanorine disc: orange or yellow, flat, epruinose margin: persistent, flush; thalline margin present, concolorous with thallus; proper margin visible, concolorous with disc parathecium: amorphous, exciple below hypothecium prosoplectenchymatous epihymenium: golden, K+ red hymenium: hyaline, 70-85 µm tall paraphyses: 2-3 tip cells slightly swollen, not branched; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 12.5-14 x 5.5-7 µm, isthmus 3-4 µm, spore end wall thin Pycnidia: not observed Spot tests: apothecial margin K+ red; thallus K+ red Secondary metabolites: parietin, fallacinal, emodin, and teloschistin. Substrate and ecology: on non-calcareous rocks World distribution: coastal western North America Sonoran distribution: southern California. Notes: Caloplaca marina subsp. americana has scattered convex areoles and lacks an orange prothallus:. It is strictly maritime. Caloplaca rosei often grows with C. marina subsp. americana but see notes under that species for separation from C. rosei.