Description contributed by Graham Kinsey, CABI, based on Wehmeyer (1933).
Anamorph: Phomopsis aquifolii (Brunaud) Keissl. (1913). Conidiomata to 300 µm diam, rarely to 800 µm diam. Conidiophores 12-20 µm x 1-3 µm. Alpha-conidia 6-12.5 x 2.5-5 µm; beta-conidia 20 x 1 µm.
Teleomorph: stromata on host surface as conical, pustulate, circular, blackened discs, 1-1.5 mm diam., or 2-4 mm diam. when on leaves and then sometimes confluent, erumpent through the closely adherent periderm and containing the ostioles either in a dense cluster or ± scattered. Ascomata 320-560 µm diam., spherical to irregular from crowding, clustered beneath the ectostroma, ostioles stout-cylindrical. Asci (50-)60-80 x 9-12 µm, clavate, with a refractive apical ring. Ascospores (12-)14-16 x 4.5-5.5 µm, later to 17 x 7 µm, cylindric-ellipsoidal to fusiform-ellipsoidal, obtuse, scarcely constricted when young, later more strongly constricted.