Thallus dark grey with brownish tinge, unevenly areolate, smooth to verrucose, orbicular or effuse, sometimes forming concentric rings, very variable in form. Prothallus black. Areoles to 2.5 mm wide, sometimes surrounded by zones where the white, necrotic prothallus shines through, with a cortex 25-35 µm thick and cells 3-5 µm diam. Isidia and soredia absent.
Anamorph: conidiomata pycnidial, with straight or rarely curved conidia (7-) 7.5-10 (-12.5) µm in length.
Teleomorph: ascomata apothecia, to 1.2 mm diam., often numerous and strongly crowded, level with the thallus or somewhat raised, with a well-defined rim that is concolorous with the disc. Exciple to 50 µm thick, J+ pale to dark blue. Hymenium 85-95 µm thick, gelatinous, with paraphyses that are somewhat swollen (submoniliform) at the apex with the upper two or three cells rounded. Epihymenium dark green (caesiocinerea-green or aspicilia-green) , N+ emerald green, K+ brownish. Ascospores (14.5-) 17-20.5 (-22.5) x (7-) 8.5-11.5 (-13.5) µm in size, hyaline, aseptate.
Not formally assessed. The species has few distinctive morphological features and may be overlooked. The only confirmed GB&I record is based on a sterile specimen that was identified using molecular methods.
The only diagnostic differential character separating Sagedia from Aspicilia species is the shorter conidia, apart from molecular data.
In GB&I, recorded from a single locality in Wales (Caernarvonshire). Historical records from Kent and Sussex are unlikely to be correct; they probably refer to Aspicilia caesiocinerea. Reported throughout Scandinavia, and also from montane areas of Austria and Italy.
In GB&I, on siliceous rocks close to the water level. In Sweden it is not restricted to streams and lakesides, but can be found also in agricultural areas, on epilittoral seashore rocks and in subalpine and alpine areas.