Thallus: squamulose squamules: contiguous or slightly overlapping, 1-3 mm wide, 0.15-0.3 mm thick, ± deeply lobate, closely adnate upper surface: pale to dark brown, smooth, dull upper cortex: 30-50 µm thick, composed of angular cells (4-9 µm wide), in ± vertical columns, with a thin amorphous, epinecral layer medulla: white, subparaplectenchymatous, composed of roundish cells (6-11 µm in diam.); algal layer: c. 50-100 µm thick; algal cells: 6-11 µm in diam., in vertical rows lower cortex: paraplectenchymatous, brown-black, 30-40 µm thick lower surface: black, bare, without rhizohyphae or rhizines; squamules attached by folds of their undersides Perithecia: subglobose, up to 0.4 mm broad; exciple: dark brown to black, c. 25 µm thick; periphyses: 40-60 µm long, simple or sparingly branched; hymenial algal cells: globose, 4-5 µm in diam. or ellipsoid and 5-7 x 3-4 µm asci: oblong-clavate, 2-spored ascospores: muriform, hyaline to pale brown, broadly ellipsoid to oblong-subcylindrical; 30-50 x 14-25/ 40-60 x 13-18 µm (distal/proximal spores) Pycnidia: immersed, ovoid, up to 0.2 mm wide conidia: bacilliform, 5-7 x 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate: soil World and Sonoran distribution: uncertain, only known from NW Mexico, probably to be found elsewhere. Notes: The type specimen of Endocarpon subnitescens has conspicuous black rhizines and agrees also in all other details with E. pusillum, however, the name E. Subnitescens has long been erroneously used for an erhizinate taxon (c. Poelt 1974). Accordingly, a new name is required. Endocarpon pseudosubnitescens is clearly distinct from E. pusillum in having neither rhizines nor rhizohyphae. Its squamules are fastened to the substrate by folds or knobs of their naked lower side, which is clearly set off the substrate, whereas E. pusillum has a more or less thick dark basal layer that merges into a weft of rhizohyphae penetrating the substrate though the squamules are mainly anchored by ± conspicuous black rhizines. Moreover, the conidia of E. pseudosubnitescens are longer, and the ascospores tend to be paler.