Life habit: lichenized Thallus: placodioid, up to 3-5 cm or more across, 0.5 mm or more thick, +attached over the whole lower surface, usually distinctly rimose-areolate, areolate or verrucose-areolate, without papillae, not chalky; +clearly lobate at margin lobes: plane to convex, broadly and tightly attached to almost free and becoming stipitate, crowded and squamule-like upper surface: continuous to rimose, pure gray to white, brown, or black, or yellowish brown to clay colored, without asexual propagules upper cortex: eucortical and paraplectenchymatous, or phenocortical with few to many dead algal cells; hyphae thin-walled, unoriented to anticlinal photobiont: primary one a Trebouxia green alga, secondary one absent; scattered to grouped or becoming distributed in areas of optimal exposure to light; penetrated by bundles of anticlinal hyphae medulla: dense to +loose, with or without hyphal bundles; hyphae: elongated, +anticlinal, mostly 2.5-4 Ám wide, +thin-walled; walls: mostly very little swollen, the outer boundary well delimited lower cortex: absent, or eucortical and paraplectenchymatous Ascomata: apothecial, lecanorine or aspicilioid, borne laminally on the central areoles, +round to irregular, up to 2.5 mm in diam., immersed to appressed or constricted sessile, sometimes aggregated or confluent disc: reddish brown to brown or black, plane or convex, pruinose or not margin: persistent, in section appearing +swollen; parathecial crown: often present, dark; cortex: diffuse brown, without special structure or texture, eucortical and paraplectenchymatous on upper and lower sides; or absent to phenocortical; algal layer: scattered or grouped, abundant in the margin, present or absent below hypothecium; medulla: paraplectenchymatous parathecium: composed of parallel hyphae with distinct, +round, thin-walled cells, the apical ones brown-capped epihymenium: diffuse pale yellowish to reddish brown, 10-15(-30) Ám thick, N- or N+ slightly greenish (without "Aspicilia-green") hymenium: hyaline, c. 75 Ám tall, I- or + pale blue to greenish, yellowish, or reddish brown; paraphyses: c. 2.5 Ám wide, septate, mostly lax, almost always unbranched, the top 3-4 cells sometimes convex and constricted at the septum (submonilliform); apical cells: short-clavate to globose, hyaline to brown; subhymenium: thin, hyaline to slightly gray, yellow or brown; hypothecium: hyaline to pale gray, yellow, or brown; hyphae: unoriented, thick-walled, gelatinized asci: oblong to oblong-elipsoid (or somewhat clavate); apical cap: I-, mostly over 10 Ám high; 8-spored, the spores irregularly biseriate ascospores: hyaline, simple, subglobose to short ellipsoid or long ellipsoid or ovoid, obtuse at the poles, 916 x 5-11 Ám, +granular and deformed in the ascus; wall: +thin, smooth, without distinct endospore thickening, not amyloid Conidiomata: pycnidial, laminal, immersed; ostioles: blackish brown, scarcely prominent; conidiophores: type IV of Vobis (1980) conidia: straight, bacilliform or short-cylindrical, 5-9 Ám long Secondary metabolites: absent, or ▀-orcinol depsidones Substrate: calcareous to siliceous rocks Geography: Eurasia; Asia; North Africa, Central America, western North America, and Australia. Notes: Lobothallia is a segregate from Aspicilia, characterized by the distinctly lobed thallus, simple (and always non-monilliform) paraphyses, usually brown (N-) epihymenium, and small spores. Although some species presently retained under Aspicilia have some of the same features, none of them are distinctly lobate, and the species of Aspicilia that are distinctly lobate have a green, N+ green epihymenium and branched, often monilliform paraphyses. Some specimens of Lobothallia might be confused with species of Protoparmelia, but Lobothallia differs in color, chemistry, and characteristics of the apothecia and spores. The taxonomy of the species of Lobothallia is poorly known; in Eurasia a large number of specific or infraspecific taxa belonging to or similar to Lobothallia have been described by Gyelnik (1931a & b, 1932) or other authors (see Kopaczevskaja, et al., 1971); although I have investigated some of these, much further and broader studies are needed to determine the taxonomic significance and positions of these taxa. The taxon described from Baja California (on sandy soil) as Lecanora castaniza Nyl. may well belong to Lobothallia, but the type (H-Nyl!) is a small, scrappy specimen mostly covered by transparent glue, and I have not made detailed investigation of it. The thallus is squamulose to short-lobed, dark brown and K-; the apothecia, immersed when young; the discs, dark brown to black; the hymenium gelatin I+ wine red; the spores 11-13 x 7-8 Ám; and the conidia 5-6 x 0.7 um.