Buellia spuria, the disc lichen, is a white to light ashy gray crustose areolate lichen that grows on rocks (epilithic) in montane habitats.

[2] It has a black edge from the conspicuous, more or less continuous prothallus, which can also be seen in the cracks between the areolas forming a hypothallus, and in sharp contrast with the whitish or ashy colored areolas.

[2] It prefers mafic (siliceous) rock substrates.

[2] In Joshua Tree National Park is can be seen on vertical granite and gneiss faces in washes.

[2] It is similar in appearance to Buellia stellulata, but has a different secondary chemistry, and B. spuria is common throughout the Sonoran Desert region, while B. stellulata is restricted to coastal regions.