Thallus orbicular, to 15 cm diam., but generally much smaller, the older central lobes and true marginal lobes which adhere to substrate are generally crowded or contiguous, broad, 3-7(-10) mm wide, commonly with peripheral and secondary lobes which are linear, suberect, elongated, narrow (1-2 mm wide) and lack lateral contacts, occasionally these cartilaginous, repeatedly dichotomously branching linear lobes become dominant and accentuate the loosely ramified character of such plants. Upper surface grey, with laminal wrinkles, upper cortex erupting and becoming sorediate, ultimately extensively covered with granular soredia commonly occurring in confluent glomerulae 3-5 mm wide. Medulla solid for the most part, white. Lower surface black, sometimes blanching in older, highly sorediate specimens, pale brown or whitish at apices, strongly wrinkled. Apothecia relatively rare, subpedicellate, with a sorediate, funnel-shaped exciple, disc red-brown, 3-7(-12) mm diam., concave at first, becoming flat with age, margins entire at first, becoming sorediate. Ascospores ellipsoid, 6-9 × 4-5 µm. Chemistry: Cortex K+ yellow; medulla K-, C-, KC+ red, Pd+ red. This species has two distinct chemodemes. (i) Atranorin, chloroatranorin, physodic, 3-hydroxyphysodic, 2'-O-methylphysodic and alectoronic ± acids. (ii) with physodalic and protocetraric acids in addition to the above compounds.