Thallus: squamulose, composed of minute, discrete or contiguous, erect or appressed, 0.1-0.2 mm wide squamules, when fully developed, deeply dissected into slightly flattened or almost cylindrical terminal segments (15-30 µm wide), scarcely covering the substrate surface: green to brown-green, not dissolving into soredia Apothecia: at first flat, later becoming slightly convex, 0.25-0.45 mm in diam. disc: orange-brown, red-brown, or black, epruinose margin: distinct, level with or raised above disc, persistent, upper part dark red-brown to black, concolorous with disc or darker, lower part paler, ±pale brown exciple: laterally c. 30 µm wide, without crystals, ±red-brown (K+ purplish, N+ orange), fading below, darkest along the edge and in uppermost part epithecium: diffusely orange-brown to red-brown in upper part (K+ purplish, N+ orange), without crystals hymenium: colorless below except for occasional vertical streaks of brown pigment, c. 60 µm tall; paraphyses: 1.5-2 µm wide in mid-hymenium; apices: ±clavate, 3-5 µm wide hypothecium: pale yellow (K+ intensifying) asci: clavate, 8-spored ascospores: hyaline, indistinctly septate or with up to 7 thin septa acicular, straight, curved or sigmoid, 32-48 x 1.5-2 µm Pycnidia: not seen Spot tests: all negative Secondary metabolites: not investigated. Habitat and ecology: on decaying Peltigera on the ground at approximately 2000 m World distribution: unknown Sonoran distribution: a single collection from the Santa Rita Mountains in southern Arizona. Notes: Bacidina "dissecta" is readily identified by the combination of minute, deeply dissected thallus squamules with extremely thin terminal segments and +brown apothecia. The thallus is reminiscent of B. squamellosa S. Ekman, but that species has pale pink apothecia and is known only from tree bark in Florida (Ekman 1996a). Bacidina neosquamulosa is also similar in being composed of squamules. However, the thallus of that species covers the substrate, often rather large surfaces, and the squamules are wider and less incised. The terminal segments of the squamules are shaped like globose granules, which are wider than the terminal segments in B. "dissecta". Bacidina "dissecta" is not described here formally due to the sparse material available.