Life habit: lichenized Thallus: absent or crustose, compact or tomentose, endo- or epiphloedal, or occasionally epilithic, thin, continuous, scurfy or cracked, to irregularly areolate or verrucose, rarely leprose, effuse or delimited by a dark brown prothallus surface: smooth to slightly granulose, or sometimes verrucose-rugose cortex: absent or poorly differentiated medulla: usually present (except when thallus very thin), chalky, usually with a layer of loosely intertwined, light brown hyphae close to the substrate photobiont: primary one a Trentepohlia green alga, secondary one absent Ascomata: apothecioid, usually +round, sessile, scattered to aggregated, lacking a thalline margin disc: dark brown to black, plane or slightly convex, very often with dense whitish, grayish or yellowish pruina, sometimes also with tomentum (composed of independently prolonged, epithecial hyphae giving the surface of the disc a tomentose or almost pubescent appearance) margin: often intensely black, sometimes white-pruinose, usually persistent, raised, exciple: well developed, dark brown internally, laterally becoming paler brown; composed of usually brown, intertwined hyphae pseudothecium: pale to dark brown or dirty brown, in a gelatinous, granular matrix with hyphae usually richly branched or more rarely reticulate or sparsely reticulate hymenium: hyaline, amyloid or hemi-amyloid; paraphysoids: septate, 1-2(-2.5) µm wide, strongly branched and anastomosed, hypothecium: dark brown asci: narrowly clavate to cylindrical, slightly stipitate, with a thick, strongly amyloid band in the endoascus, with a ring structure and a small ocular chamber without apical nasse, 8-spored ascospores: hyaline, sometimes brown when old, transversely 3-7-or more septate, fusiform or acicular-fusiform Conidiomata: pycnidial, usually prominent, immersed to sessile, sometimes with a dense whitish pruina conidia: hyaline, simple, filiform Secondary metabolites: thallus usually containing phenolic substances, including orcinol depsides or ß-orcinol depsidones Substrate: mostly on humid, yet dry, shaded rocks and dry recesses of bark Geography: temperate to subtropical areas, especially in oceanic influenced localities. Notes: Lecanactis may be confused with various other genera in the Arthoniales (see notes under Bactrospora, Cresponea, and Lecanographa). Sigridea and Schismatomma (Roccellaceae) differ in having a thalline margin on the apothecia and a poorly developed exciple Lecanactis abietina (Ach.) Körb., that is also P- and has spores up to 40 µm long, was reported by Hasse (1898a) and Orcutt (1907) from southern California (respectively the San Gabriel Mountains and Torrey Pines), but we have not seen authentic material. Because Hasse (1913) does not mention the latter species in his flora, we assume that the specimens were annotated to the species treated below.