Pseudothecia: black, immersed, 0.14-0.2 mm in diam. ascomatal wall: brown, somewhat paler towards the base, laterally c. 20 µm thick, composed of tangentially flattened cells, in the upper part darker brown, up to 40 µm thick and cells subspherical paraphysoids: absent in mature ascomata periphyses: simple or branched, 7-15 x 1.5 µm asci: 50-65 x 10-15 µm, 8-spored; wall: thickened in about the upper third ascospores: pale to medium brown (pigment appearing relatively late), 1-septate, with transverse septum (both cells more or less equal in shape and size), +constricted at the septum, 16-20 x 5-7 µm; wall: thin and smooth, without visible perispore Pycnidia: not seen. Host: on the thallus of Dimelaena oreina World distribution: North America (U.S.A. and Mexico) Sonoran distribution: Sonora and Chihuahua. Notes: The material of Endococcus on Dimelaena oreina was treated by Triebel et al. (1991) as belonging to E. perpusillus Nyl. using a wider species concept. Hafellner et al. (2002) distinguished Endococcus oreinae from E. perpusillus s. str. by its larger pseudothecia, larger ascospores and a different host selection (E. perpusillus s. str. grows on Schaereria fuscocinerea).