Thallus crustose, verruculose, ashy glau-cescent, white or brownish glaucescent, more or less continuous. Apothecia 0.7-2.0 mm broad, flattened, brown-black to black, shining, epruinose; margin soon disappearing; disk minutely rugose; exciple pale or red-brown, radiate, the lower side of apothecium appearing as palisade plecten-chymatous; hypothecium hyaline to light brown, not as dark brown as in Micarea melaena; epihymenium pale or brown; hymenium hyaline to brownish, outer part brownish, 90-120 ¡xm, 1+ blue turning purplish; paraphyses 1-2 μm, tips thickened, not branched, gelatinous, very coherent; asci clavate; spores biseriate, ellipsoid with acute tips, 3-septate, 16-34 x 6-8 μm.

Reactions: K—, C—, P—; when margin is reddish, KOH turns it violet.

This species grows on soil, humus, old wood, and occasionally bark. It is circumpolar arctic to boreal.

Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: crustose, continuous, rather thick surface: gray, coarsely granular or warted Apothecia: single or in groups, 0.4-1.4 mm in diam., at first almost flat but soon becoming convex and ±globose disc: gray-brown, orange-brown, or red-brown margin: concolorous with disc or paler, at first distinct, level with disc, soon excluded and reflexed exciple: irregularly pale yellow (K+ intensifying), pale brown, and red-brown (K+ slowly purplish) in upper part, darkest in parathecial crown, merging with hypothecium pigmentation, fading below, laterally c. 90 µm wide hymenium: colorless below, upper part diffusely pale brown to red-brown (K+ slowly purplish), 60-90 µm tall paraphyses: 1.5-2 µm wide in mid-hymenium; apices: ±clavate or not at all thickened, 2-5 µm wide hypothecium: colorless, pale yellow (K+ intensifying), or partly brown to red-brown (K+ slowly purplish) asci: clavate, Biatora-type, 8-spored ascospores: hyaline, 3-septate, fusiform, straight, 16-28 x 5-8 µm Spot tests: all negative Secondary metabolites: none detected. Habitat and ecology: on bryophytes or soil at c. 3500 m World distribution: arctic and alpine areas as well as temperate mountain forests in North America and Europe Sonoran distribution: known from a single locality on Mount Humphrey in central Arizona. Notes: Mycobilimbia tetramera is very similar to M. carneoalbida and differs from this species mainly in the richer apothecial pigmentation and slightly longer ascospores.