Photos are of specimen while wet. On concrete, east facing side of multi story building, second story. Lower surface with patches of white tomentum, image 5. Attempted thallus cross section, image 7. Spores muriform. Last photo is of a thin slice of cortex, showing jigsaw puzzle piece shaped cells.
Intertidal lichen! That was the theme of the day, of course. Found and pointed out by Shelly. Note the perithecia (little bumps), and the fact that it otherwise looks like every other black encrusting algae (?) in the splash zone.
very wet redwood forest after days of rain. on fallen twig.
Keyed out with the expert help of Shelly Benson at the Hopland Lichen Foray @sbenson