Thallus: crustose, dispersed-verrucose to verruculose or continuous to nearly byssoid, ecorticate; prothallus: not visible or black surface: yellowish white to yellowish gray or whitish gray, epruinose, with an indistinct margin, esorediate Apothecia: sessile, 0.2-0.5(-0.8) mm in diam., lecanorine disc: pale to dark red-brown, epruinose margin: concolorous with the thallus, thick, verrucose to verruculose, without a parathecial ring amphithecium: present, with numerous algae, with large and small crystals, corticate; cortex: hyaline, interspersed, slightly thickened basally, c. 15 µm thick laterally and 15-20 µm thick basally parathecium: hyaline, 10-15 µm thick, with numerous small crystals soluble in K epihymenium: reddish brown, 10-15 µm thick, pigmentation not altered in K, without crystals hymenium: hyaline, clear, 65-95 µm tall; paraphyses: sparingly branched and not to slightly thickened (up to 2.5 µm wide) apically; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 11.5-17 x 6.5-9 µm Spot test: thallus and apothecial margin K+ yellow, C+ orange, KC+ orange, P+ yellowish orange Secondary metabolites: atranorin (major), chloroatranorin (minor), chodatin (major), demethylchodatin (submajor), 3-O-methylthiophanic acid (minor), thiophanic acid (minor) and zeorin (major). Substrate and ecology: on bark World distribution: pantropical, known from rainforest edges, savannahs and gallery forests throughout the tropics Sonoran distribution: Baja California Sur and Chihuahua. Notes: Lecanora tropica is easily recognized by its small apothecia with a red-brown apothecial disc, the egranulose epihymenium, large amphithecial crystal, and te prsence of the chodatin chemsyndrome. Similar species in the area studied include L. neonashii and L. pseudargentata. The differences are discussed under these species. This is the first record of L. tropica from North America.