Thallus: foliose but almost crustose, closely appressed to agglutinated up to the lobe tips, 3-6 cm in diam., pinnately or subpinnately lobate lobes: radiating, slightly disjunct or merely adjacent, flat or convex but sometimes concave towards the apex, 0.5-1.2 mm wide, plicate and rugose centrally, not or hardly flabellate towards the lobe tips upper surface: yellowish gray, greenish gray, gray, lead gray, bluish gray, darker at the apex, with a punctiform, rarely patchy white pruina, without soralia, isidia or polysidiangia pseudocyphellae: often distinct, marginal and laminal, usually restricted to the peripheral parts of the lobes, sometimes reticulately confluent medulla: white, the lowest part sometimes orange, especially towards the lobe tips lower surface: black in center, paler towards lobe tips, erhizinate Apothecia: very common, laminal on thallus, 0.5-1 mm wide disc: black, usually not or only slightly gray pruinose ascospores: brown, 1-septate, ellipsoid, 10-15 x 4.5-6 µm Pycnidia: immersed in warts conidia: bacilliform, 4-5 x 1 µm Spot tests: upper cortex K+ yellow, C-, KC-, P+ yellow; medulla upper and lower part K-, C-, KC-, P- Secondary metabolites: upper cortex with atranorin; medulla with divaricatic acid and few terpenes in low concentration. Substrate and ecology: on rocks, from sea level to the edges of montane rain forests World distribution: in tropical and subtropical regions of North and South America Sonoran distribution: ranging from arid transition areas to oak-conifer forests of Arizona, Baja California Sur, Chihuahua and Sonora. Notes: Dirinaria neotropica is similar to D. confluens, but is easily separated by its smaller ascospores. The holotype (from Uruguay) of D. confusa var. saxicola is gray, but two paratypes from Mexico (M, UPS) show a yellowish tinge of the lobes which is typical for many specimens cited above. Dirinaria confusa contains sekikaic acid and ramalinolic acid in addition to atranorin, but contrary to the statement of Awasthi (1975), who found no divaricatic acid in his var. saxicola, this substance could be verified in the holotype as well as in the investigated paratypes by TLC. Nevertheless, D. neotropica as circumscribed here seems still variable, e.g. the color of the lower cortex can vary from jet-black to light brown. In an earlier state of the preparation of the manuscript for this paper, the specimens with a bright lower surface were treated as Dirinaria complicata, but that species has still bigger ascospores than Dirinaria confluens. A close relationship of D. neotropica with D. adscensionis must also be considered. Genetic methods should be sought to solve these problems.