Thallus: foliose, loosely adnate to partially free growing, pulvinate, forming intact rosettes, 4-8 cm in diam., irregularly lobate lobes: sublinear to subirregular, short, plane to +convolute, separate and strongly imbricate (together with the lobulae several layers thick), 1-3 mm wide, becoming lobulate centrally lobules: convex, rarely sub-terete, 0.1-0.4(-0.8) mm wide, subascending; main apices: subtruncate, smooth to crenate, eciliate upper surface: yellow-green, smooth, shiny, epruinose and emaculate, without soralia, isidia, or pustulae medulla: white, with continuous algal layer lower surface: pale to dark brown, moderately to densely rhizinate; rhizines: brown, simple, often projecting beyond the lobe margin, 0.2-1 mm long Apothecia: common, substipitate, 1-3 mm wide, laminal on thallus; disc: cinnamon-brown to dark brown; margin: smooth, pruina absent asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 7-8 x 4-5 µm Pycnidia: common, immersed conidia: bifusiform, 5-6 x 0.5 µm Spot tests: upper cortex K-, C-, KC-, P-; medulla K+ yellow to dark red, C-, KC-, P+ orange Secondary metabolites: upper cortex with usnic acid (major); medulla with salazinic acid (major) consalazinic acid (minor), and usually norstictic and protocetraric acids (trace). Notes: Typically X. wyomingica is an alpine species of the intermountain west in North America. To a degree there Substrate and ecology: on acidic is near morphological convergence with the salazinic acid pebbles and soil, often in open, alpine containing populations of coastal California and Baja Cali-habitats World distribution: western fornia, but these populations are not as strongly imbricate North America Sonoran distribution: as X. wyomingica. The coastal populations often occur on occasional in alpine and subalpine in soil, but the alpine X. wyomingica almost always is at-Arizona, coastal in southern California atached to pebbles. and Baja California.