Thallus: caespitose, soft, highly variable in shape, but always bushy branches: pliable to rigid, thicker and lacunose in inland populations intergrading to thinner populations in coastal areas, up to 3 mm in diam. (usually less), 2-5 cm in length, with either pointed or blunt branch tips surface: pale yellow to green, wrinkled to smooth, often with black stippled maculation cortex: usually a sheath of prosoplectenchymatous tissue in a gelatinous matrix lacking supportive tissue, but variable, becoming rigid and thicker with supportive tissue in some forms; branches varying from rigid and breaking when bent to softer and flexible (not breaking) medulla: medulla white, cottony, hyphal aggregates of N. homalea absent, but a few hyphae occasionally adherent Apothecia: common, present on most thalli, terminal or subterminal, sometimes with a spur, solitary or in clumps, 2-5 mm in diam. disc: pale buff or the color of the cortex, concave or flat; margin: frequently black rimmed asci: clavate, 8-spored ascospores: hyaline, 1-septate, fusiform to oblong, curved, 4.5-15.5 x 2.5-5 µm Pycnidia: variably present, black, immersed conidia: straight, rod-shaped Spot tests: either all negative or K+ yellow to orange or deep red or P+ orange if salazinic or norstictic acids present Secondary metabolites: triterpenes, zeorin, (-)-16α-hydroxykaurane, +salazinic acid, usnic acid, T3 triterpene fide Spjut (1996) and +norstictic acid; or no acids but usnic acid in synonymized taxa fide Spjut (1996). Substrate and ecology: a common, caespitose species on shrubs, trees and cacti, rarely on rock, often with N. cephalota; extirpated in much of its historic range in southern California World distribution: western North America from central coastal California, the California Channel Islands, to the Vizcaíno Peninsula and islands adjacent Baja California Sur, and South America from central Peru to central Chile Sonoran distribution: central coastal California to Baja California Sur, the Channel Islands and the islands off the western coast of Baja California. Notes: Niebla ceruchis is the most common species in the genus occurring on shrubs and trees; the only other Niebla on bark substrates being the sorediate N. cephalota. It is a highly variable and polymorphic taxon, ranging from thalli with wrinkled surfaces to more thinly branched and smoother morphologies, with a complete range of intergrades between them. The color is also variable, from yellowish green to green with black stippling. The degree of maculation varies from conspicuous to inconspicuous. Apothecia are common, and are either solitary or in clumps on the terminal areas of branches. Black pycnidia are also common. In lacunose morphologies the pycnidia occur along the ridges of the cortical wrinkles. A white, cottony exudate is exuded from thallus cracks in herbarium specimens. The extremes in morphology from the wrinkled, more yellow inland forms grading into thinner branched, stipled coastal forms are present in both North and South America and are not of taxonomic significance.