Species: Megalaria grossa
Photos: The Burren, Co. Clare, Glengarriff woods, Co. Cork, Ireland
Thallus pale green-grey or whitish, +/- smooth, often with black prothallus. Large matt-black apothecia, the thick shiny margins excluded as disc becomes convex. The asci are 8-spored, the spores 1-septate, 20-30 x 10-15 Ám. Isidia and soredia are absent. Microscope photographs below.
Thallus: Chemical reactions negative. Hypothecium dark blue-green, K+ green.
Found in old, humid woodlands in West and SW Ireland on nutrient-rich bark of Ash, Field Maple and Hazel.
Similar: M. pulverea Thallus K+ yellow, P+ red, yellow or negative