White crustose lichen on concrete slab.
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
Probably an Aspicilia but its not possible to be certain which.
Ochrolechia parella has a very different appearance and is found on rock rather than concrete: http://www.irishlichens.ie/pages-lichen/l-109.html
Lat/Lng: 49.6, 11.1