Thallus: thin or lacking, indistinctly areolate, white, esorediate; prothallus: not developed or very indistinct areoles: flat, irregular and indistinct medulla: white, I+ intensely violet Apothecia: black, sessile, with markedly or strong constricted base, up to 2.5(-4) mm in diam. disc: black, flat to moderately convex, epruinose or slightly pruinose margin: black, persistent, dull to shiny exciple: blackish green to black in a thin rim peripherally, 60-150 µm wide epihymenium: dark green, or green-brown 12-18 µm thick hymenium: hyaline or faintly green, (40-)45-55(60) µm tall; paraphyses: simple, occasionally branched, especially towards the apical ends subhymenium: hyaline, 14-45 µm thick hypothecium: dark brown below, hyaline above asci: clavate, Lecidea-type, 40-50 x 1317 µm, 8-spored ascospores: hyaline, simple, oblong to oblong-ellipsoid, (7-)8.5-12(-14.5) x (2.5-)2.9-4.4(-5) µm Pycnidia: semi-immersed; 90-150 µm in diam. conidia: bacilliform to filiform, +straight, 9.5-14(-15.5) x 1-1.3 µm [studied in 4 specimens] Spot tests: cortex and medulla K-, C-, KC-, P- Secondary metabolites: confluentic acid syndrome. Substrate and ecology: in open habitats on granites, schist and other acidic rocks World distribution: bipolar and extending into the tropics in alpine areas Sonoran distribution: rare in subalpine and upper montane belts of Arizona. Notes: Lecidea promiscens is a close relative of Lecidea auriculata, differing in having slightly larger ascospores and a less pronounced exciple. Poorly developed and ill-treated specimens may be difficult to determine. Lecidea auriculata is more an alpine-arctic element of more humid climates, while L. promiscens occurs in mountain ranges with a more arid climate. The etymology is not yet clear. The epitheton seems to be derived from Latin 'promiscuous', which means 'intermingled' as well as 'ordinary' or 'common'.