Buellia peregrina

Buellia peregrina is a species of saxicolous (rock-dwelling), crustose lichen in the family Caliciaceae. It is found in the Namib desert in Namibia.

Taxonomy
The lichen was formally described as a new species in 2007 by lichenologists Frank Bungartz and Volkmar Wirth. The type specimen was collected between Swakopmund and Hentiesbai in the Namib (a coastal desert in Southern Africa). The species name originates from the Latin word peregrinus, ("foreign"). This signifies that all specimens were discovered on allochthonous limestone, meaning stones not originally part of the sediment layer in that specific region. It is the only species in genus Buellia that grows euendolithically, i.e., with its thallus entirely within its rock substratum.

Description
The thallus of this crustose lichen has a pale beige to rose surface that changes the colour of the white limestone it inhabits. A is present but barely distinguishable from the. The apothecia are and initially immersed in cavities; they typically measure 0.2–0.4 mm in diameter. They emerge at maturity with a black, plane, and epruinose to faintly pruinose that becomes convex.

The of the apothecia is thin and black, with a narrow, poorly differentiated  containing deep blue and reddish-brown pigmentation. The hymenium is hyaline, and the are simple to moderately branched with a deep blue pigmented cap. The is deep blue (a distinctive  of this species), while the  is reddish-brown. The asci are 8-spored and, with oblong to ellipsoid, one-septate that do not display any ornamentation. were not observed in this lichen. Collected specimens did not contain any detectable lichen products.