Thallus ± closely attached, forming regular or irregular rosettes which may coalesce to form extensive patches, or surrounding small twigs and then irregular or fragmentary, to 10 cm diam., often much less, corticolous, lignicolous or saxicolous. Lobes numerous, often noticeably radiating and contiguous at margins, ± irregular towards centre and there often imbricate, 1-2.5 mm wide, margins sinuous-contorted, sometimes notched, not, or sparingly blackened at apices, apices not suffused-brownish, blunt, hollow, lower side of internal cavity brownish-black. Perforations numerous to somewhat sparse, plane or slightly elevated, 0.5-0.8 mm diam. Upper surface pale grey or greyish-white, dull, matt, often minutely pruinose in parts, occasionally shining in parts, smooth or frequently ± corrugate-ridged (×10 lens), sorediate. Soredia numerous, laminal, not associated with perforations, often in groups or widely dispersed on the lobes, sometimes confluent, convex from the first, sometimes eventually globose, coarsely granular, white, soralia < 2 mm diam. Apothecia occasional to rare, discrete or sometimes clustered, sessile to subpedicellate, 2-4(-6) mm diam., disc concave at first, becoming plane, red-brown, epruinose, margins thin, becoming sorediate. Epithecium red-brown, 35-50 µm tall, not granular. Asci 2-spored, 90-100 × 35 µm. Ascospores 48-60 × 25-30 µm. Chemistry: Stictic, norstictic (tr.) and menegazziaic acids and accessory substances; medulla K+ yellow → orange, C-, KC+ orange, Pd+ orange.