Thallus: decumbent (prostrate) to ascendent and shrubby, 1-7 cm in diam., loosely adnate, not attached at the apices, usually forming loose to dense, rather thin (1-2 mm) mats branching: frequent, divergent, regularly isotomic-dichotomous, often interwoven branches: up to 1 cm long, usually ± terete throughout (to slightly compressed towards base), ± evenly thin (0.1-0.2 mm near base, 0.05-0.1 mm near tips); internodal distance generally long, (0.5-) 1-3 (-5) mm, giving a loose hairy appearance to the thallus surface: dark brown to black, shiny to satiny, sometimes paler at base Apothecia: usually very rare, up to 5.5 mm diam.; disc: gray-black or brown ascospores: broadly ellipsoid, c. 7-12 x 6-8 µm Pycnidia: on tubercles, abundant and conspicuous, especially near the axils, up to 0.5 mm diam., black conidia: bifusiform, 5-7 x 1 µm Spot tests: K-, C-, KC-, P-, UV- Secondary metabolites: none detected. Substrate and ecology: on acidic rock faces and boulders (especially igneous rocks, sometimes shale), rarely on wood; usually on exposed rocky ridges or boulders in wind-swept sites, usually in regions with a continental climate, but in somewhat moister areas than P. minuscula; also reported from dry, sandy, or stony ground World distribution: circumpolar in both the Southern and Northern Hemispheres; low to high Arctic and temperate regions in subalpine to alpine sites Sonoran distribution: southern California and from Baja California (Guadalupe Island) as the type collection of Alectoria pacifica (Brodo and Hawksworth 1977). Notes: It is not likely to be confused with other lichens, other than slender morphs of P. minuscula. The description based on the North American literature on the species in general. It has apparently not been collected in the Sonoran region since the late 19th century.