subsp. nov. Diagnosis: Subspecies non lichenosa; a subspeciei typica lichenosa, Arthoniae phlyctiformis subsp. phlyctiformis, etiam differt ascosporis latioribus, 23-30 x 13-18 µm. Life habit: lichenized Thallus: inconspicuous, pale, endophloeodic photobiont: absent (scattered clusters of coccale algae present, without clear indication of lichenization) Ascomata: ± round, maculiform to elongate, 0.1-0.5 x 0.3-2 mm disc: black, with rough surface epihymenium: olivaceous brown to brown (towards the surface), 10-15 µm thick hymenium: hyaline, 40-60 µm tall; paraphysoids: branched and anasomosed, 2 µm wide; subhymenium: hyaline, 10-20 µm thick asci: subglobose, 40-50 x 25-32 µm, 8-spored, with slightly thickened lateral walls ascospores: hyaline, muriform (with 6-8 straight transverse septa and 1-3 longitudinal septa in each transverse segment, ovoid to almost ellipsoid, 25-30 x 12-17 µm, with a thick (1-1.5µm) gelatinous epispore Pycnidia: globose, black (in section olivaceous brown to broan, 0.06-0.08 mm in diam. conidia: bacilliform, 5-6.5 x 1 µm Chemical reactions: ascomatal gels I+ blue, KI+ blue; asci with KI+ blue tholus ring-structure; epispore I+ red, KI-. Substrate and ecology: so far known from oak twigs World distribution: known only from the type in central California (San Benito Co.) but expected further south. Notes: Arthonia phlyctiformis subsp. californica is distinguished by its thick gelatinous sheath around the spores. The European type subspecies differs by having narrower ascospores and a distinctly lichenized habit. Subspecies phlyctiformis is found on the Iberian Peninsula of Europe.