Thallus: foliose, irregularly spreading, loosely attached, with free and subascendent margins, 4-8(-10) cm in diam., somewhat coriaceous, pliable, flabby when moist, rather brittle when dry, ±regularly dichotomously lobate lobes: rather narrow, (1.5-)2-5(-7) mm wide, divergent at apices, discrete, contiguous to somewhat entangled centrally, plane; apices: blunt, rounded or shallowly furcate; margins: entire, sinuses smoothy rounded upper surface: olivaceous to bright lettuce green when moist, pale green-gray to olivaceous or buff when dry, dull, minutely punctate-impressed to irregularly dimpled in parts, ±uniformly smooth, minutely white-maculate (x10 lens) forming a faint, irregular white marbling of upper surface, without isidia, phyllidia or soredia medulla: white, K- photobiont: a green chlorococcoid lower surface: pale cream-colored or buff, often somewhat canaliculate, smooth to irregularly wrinkled or ridged, glabrous at or near apices, sparsely to moderately tomentose centrally; tomentum: silky to felted-entangled, pale buff to brown-black cyphellae: common, scattered, rounded, regular, small 0.05-0.3(-0.5) mm in diam., with sharply defined margins, conspicuously raised above lower cortex and tomentum, with white or cream basal membranes Apothecia: not seen Pycnidia: scattered, at or near margins, immersed, ostiole red-brown to brown-black conidia: hyaline, bacilliform with slightly swollen apices, 4-5 x 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on bark, still very poorly known and understood World distribution: West Indies (Jamaica, Cuba) and Mexico Sonoran distribution: south side of Mt. Evermann at 700 m on Isla Socorro in the Islas Revillagigedo south of the tip of Baja California Sur. Notes: Palaeotropical and South American specimens referred to this name belong in other taxa, e.g. Sticta dichotoma for narrow-lobed species from Indian Ocean islands, and S. ainoae for collections from temperate South America (Galloway 1994b: 38). Hafellner (1995) synonymized the S. damaecornis with S. canariensis, but the former was described in 1788 and the latter in 1809, and as a consequence the name S. damaecornis takes precedence (Galloway 1994b & 1995). In addition, the two taxa appear distinct and are not given as synonyms here. Technically Isla Socorro lies south of the Sonoran region, but the species may eventually be found within the area.