Rhizocarpon intersitum  

Resembles Rhizocarpon distinctum, but the ascospores are 3- (to 4-) septate or submuriform, soon blackish green, 20–24 × 8–10 μm; epithecium greenish in K; exciple purplish in K; medulla J–. The GB&I material has ascospores with 3–4 transsepta and 1–2 longisepta, measuring 24–29 (–33) × 9.5–12 μm.