Thallus: thin, superficial, membranous to rimose upper surface: greenish to olive-gray, smooth prothallus: absent Perithecia: immersed, dispersed, 0.3 to 0.5 mm diam.; ostiole: dark brown; involucrellum: absent; exciple: colorless below, brownish above; hamathecium: composed of persistent paraphyses, richly branched and anastomosed; periphysoids towards the inner side of the ostiole; periphyses absent asci: cylindrical, 4- to 8-spored ascospores: brown, muriform, with 6-8 lateral and 2-3 longitudinal septa, ellipsoid to narrowly ellipsoid, 25-40 x 10-17 µm Pycnidia: not seen Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on bark (Juglans californica and Prunus ilicifolia) World distribution: southern California and Mediterranean Europe Sonoran distribution: the Santa Monica Range and Catalina Island in southern California. Notes: This species is characterized by its relatively thin thallus and brown ascospores. In contrast, Thelenella modesta has colorless ascospores.