Megalaria laureri

Thallus whitish to grey-green, rimose, thin and smooth, or to 150 μm thick with a granular-warted surface; prothallus fimbriate, white, rarely visable, thallus typically delimited a black antagonism line; photobiont cells 6–14 μm diam. Apothecia 0.4–1.1 mm diam.; disc flat to slightly convex; true exciple shallow, often paler than the disc, colourless or sometimes brownish (concolorous with the epithecium) at the upper outer edge, at base of apothecium often concolorous with the hypothecium, swelling in K, the hyphae distinctly radiating, branched and anastomosing, 1.5–2 μm diam., without swollen ends; epithecium dark purple-brown, K+ purplish, N+ red, sometimes with additional patches of greenish, K+ green, N+ red pigment; hymenium 65–80 μm tall, colourless to pale purple brownish; hypothecium purple-red, K+ purple in the upper part (subhymenium); lower part pale golden-brown, K–; paraphyses 1.3–1.7 μm diam., unbranched, the apices clavate to 3 μm diam., cemented by adhering pigment. Asci Bacidia-type, with a distinct apical cushion. Ascospores 12–18 × 5–7 μm, ellipsoidal to fusiform-ellipsoidal. Pycnidia not found. Thallus C–, K+ pale yellow, Pd–, UV–.

Superficially resembles some morphs of the common Lecidella elaeochroma, which can be readily distinguished using chemical reactions. The pale margin contrasting with the darker disk is distinctive when well-developed, but morphs with less contrasting margins exist and are more difficult to pick out.