Ionaspis lacustris  

Thallus to 400 µm thick, epilithic, smooth, even, continuous or irregularly cracked (especially around the apothecia), usually deep orange-brown, becoming white-cream in shade, effuse or mosaic forming and then delimited by a red-brown prothallus. Soredia and isidia absent. Photobiont Trebouxia.
Anamorph: conidiomata pycnidia 50-80 μm diam., red-brown. Conidia 4.5-6.5 × ca 1 μm.
Teleomorph: ascomata apothecia, 150-400 (-600) µm diam., sometimes clustered, immersed but often developing a slightly raised proper margin, usually rounded and regular, the disc pale orange to rusty red-brown, but paler when wet. True exciple internally hyaline, the uppermost and outer parts pale brown to red-brown, the outer edge granular, without included photobiont cells. Epithecium pale orange to dark red-brown, interspersed with minute brown granules not dissolving in K. Hymenium 90-105(-200) μm high, K–, N–. Hypothecium ± hyaline. Interascal tissue of robust thick-walled unbranched paraphyses, not swollen at the apex. Asci clavate to cylindrical, the outer coat K/I+ blue, the inner walls and apical dome K/I–,  8-spored. Ascospores arranged biseriately, 13-20 × 6-11 μm, broadly ellipsoidal to subglobose or broadly ovoid, hyaline, aseptate, fairly thick-walled, sometimes with a distinct perispore.