Coccocarpia erythroxyli

Apothecia are hemispherical granular domes adhering tightly to the cortex of the thallus. They progress from reddish-brown to brownish-black with age. Instead of green algae, this lichen forms a symbiotic partnership with a cyanobacteria (Scytonema).

The lower surface forms a thick, dense layer of black tomentum that frequently overlaps the margins of the lichen, sometimes greatly so. The upper surface of the thallus (cortex) is gray with a slight bluish tint.