Lecanora muralis (Protoparmeliopsis muralis) is a waxy looking, pale yellowish green crustose lichen that usually grows in rosettes radiating from a center (placodioid) filled with disc-like yellowish-tan fruiting bodies (apothecia).

[1] In California, it may be the most common member of the Lecanora genus found growing on rocks (saxicolous).

[1] It grows on rock including basalt, pumice, rhyolite, granite, sandstone, and limestone.

[2] In California, it may be the most common member of the Lecanora genus found growing on rocks (saxicolous).

[2] The usually 1.5–3.5 cm (or more) wide nonvegetative body (thallus) is made up of parts separated by cracks (areolate) that may lift at their edges (squamulose), usually growing in a neat rosette radiating from the center (placodioid in lobes.

[2] Contiguous or widely separated lobes radiate outward, but may be randomly oriented.

[2] The center of the apothecia is orange to red-brown, sometimes greenish gray to black near the margins.

[2] The fungal filaments (hyphae) of the upper cortex are either randomly oriented to becoming anticlinal, and are 3–5 μm in diameter.

[2] The algal layer is thickened and divided into a lower surface that is white or pale to deep-yellow or brown.