Caloplaca yorkensis S. Y. Kondr. & Kärnefelt  

Mycobank MB 517748

Thallus (0.3–)1–2 cm wide or aggregated into larger colonies forming grey to greyish brown, somewhat indistinct areas of different thickness, from indistinct, almost endolithic or very thin and immersed in the substrate, cracked together with the substrate forming areoles, 0.4–0.7 mm wide, to rather thick and well-developed, (to 0.3 mm thick), plane or subconvex, immersed to ± exfoliating; areoles grey or greyish white to brownish grey with sparse, often minute, biatorine, dull yellow orange apothecia. Apothecia to 0.3–0.6(–0.7) mm diam., 0.2–0.25 mm thick in section, biatorine, usually scattered and regularly rounded, rarely irregular due to mutual pressure; proper margin pale yellowish or concolorous with disc, becoming excluded; disc plane to subconvex, dull yellow orange to brownish yellow-orange, in section biatorine, true exciple 30–50 µm thick in uppermost lateral part and to 40 µm thick in lower lateral part, 30–70 m thick at the base, pseudoprosoplectenchymatous to somewhat mesodermatous paraplectenchymatous with a well-developed matrix in the centre; hymenium 50–60 µm high; subhymenium 20–25(–70) µm thick; epihymenium bright yellow; paraphyses 1.5–2 µm diam., distinctly swollen to 4–5 µm diam. towards the tips; asci 2–4–6–8-spored, often mature bipolar and simple undeveloped or abortive ascospores present; ascospores small and very narrow, slightly swollen at the septa, 9–11(–12) x 3.5–5(–6) µm in water and (8–)9–12 x (4–)4.5–6(–7) µm in K, with rather thin septum, (1.5–)2–3.5 µm wide in water and 2.5–3.5(–4) µm wide in K. Secondary chemistry: epihymenium K+ purple to crimson purple, becoming brownish crimson on standing.