Life habit: lichenized Thallus: crustose, immersed, evanescent, rimose, warted, areolate, or granular, effuse (rarely with effigurate margins), attached by hyphal rhizoids surface: white, gray, green, brown or black, lacking soredia and isidia anatomy: poorly differentiated, upper cortex either absent or rudimentary, without a lower cortex; medulla I- photobiont: primary one a chlorococcoid (e.g., Trebouxia, Myrmecia, Dictyochloropsis) green alga, secondary one absent, mostly in small groups dispersed throughout thallus Ascomata: apothecial, immersed to sessile, solitary or clustered, small (0.3-1.5 mm in diam.) disc: pale to dark, variously colored, dull or glossy, round, ±concave to plane or moderately or strongly convex, usually epruinose; thalline exciple: absent exciple: well developed in most species, usually evident and swollen at least when young, persistent or disappearing, composed of coherent (in K), branched, radiating hyphae epihymenium: hyaline to black hymenium: hyaline, (30-)40-60(-75) µm tall; paraphyses: simple or sparingly branched (more branched towards tips), free, septate, the apices abruptly swollen (up to 5-8 µm wide) and with a dark brown apical cap (Catillaria s. str.), or the apices swollen or not and either hyaline or surrounded by a pigmented hood; hypothecium: pale or dark asci: clavate-cylindrical, unitunicate, rather thick-walled, tholus I+ blue, with a blue outer coat in K/I and uniformly blue apical dome (Catillaria-type) or with a K/I- conical apical cushion (Bacidia- or Biatora-types) ascospores: hyaline, 1-septate, oblong-ellipsoid, ovoid or bean-shaped, with rounded or pointed ends, thin-walled, 6-16 x 2-6 m, 8(-16)-spored Conidiomata: pycnidial, usually immersed and inconspicuous; conidiogenous cells enteroblastic, arranged in chains with conidia borne terminally and laterally, or in a single layer and broadly ampulliform, acrogenous or pleurogenous conidia: hyaline, simple, ellipsoid to bacilliform Secondary metabolites: mostly no substances; some species with usnic acid or atranorin Substrate: on bark, rock, or soil Geography: best developed in the tropics (according to Galloway), but also well represented in temperate to boreal areas. Notes: Catillaria in the broadest sense is characterized by lecideine to biatorine apothecia with small to moderate-sized, hyaline, 1-septate spores usually 8/ascus. It is still heterogeneous, and its relationships to other genera have not yet been fully clarified. Catillaria s. str. is characterized by asci with uniformly K/I+ blue apical dome, the abruptly swollen paraphysis tips with a dark brown cap, non-halonate ascospores, and the conidogenous cells in chains. Coppins (1992) lists Kiliasia as a synonym, but Timdal synonymizes it under Toninia. Genera that can be confused with Catillaria include: Catinaria, which has thick-walled halonate ascospores and contains Trentepohlia as the photobiont; Megalaria, which has an apical cushion in the ascus tips, mostly branched paraphyses, and thick-walled ascospores; Micarea, which has small, thin-walled photobiont cells often in pairs and asci with an axial mass; and Cliostomum, Toninia, and Lecania, all of which have asci with an axial mass and ocular chamber; Cliostomum has conspicuous pycnidia and the thallus usually contains lichen substances; Toninia usually has a squamulose thallus; Lecania usually has lecanorine apothecia at least when young, and both of the latter genera have filiform conidia. The lichenicolous genus Scutula has asci with a diffuse axial mass. In addition to the species reported below, there is a literature report of Catillaria endochlora (Fée) Zahlbr (Fink 1935) from California (location unknown) based on earlier reports, which in fact do not mention the species from California. Therefore, it is deleted from the descriptions as a probable mistake. Catillaria globulosa (Flörke) Th. Fr., a species reported from Arizona, is treated under Biatora (Vol. II) and therefore is not treated here. The treatment of this genus is problematic for at least two major reasons. First, it is in urgent need of monographic analysis and is widely recognized as being polyphyletic, but the proper boundaries for revising the plethora of species called Catillaria are not yet clear. Second, we have been hampered by inadequate material, both because of a very limited collection base and because a significant fraction of those limited collections has apparently been misplaced in Graz, and hence were not available for analysis. Consequently, we have been forced to accept literature reports for several species, some of which are doubtlessly incorrect. Descriptions below for C. chalybeia, C. lenticularis and C. subviridis are primarily based on Kilias (1981); the others are primarily based on Fink (1935) and Hasse (1913).