This is probably the most commonly encountered large, hemispherical Annulohypoxylon in North America. It has large (from about 0.5 cm up to about 5 cm diameter; typically 1-2 cm) hemispherical to spherical stromata with mostly inconspicuous perithecial mounds, and is black or dark brown in colour with very dark granules immediately beneath the hard outer crust (visible with dissecting microscope). The interior tissues have a vaguely zoned appearance, with radial structure from the attachment point, and are woody or hard-corky in texture; the interior has much the same feeling as well a piece of charcoal. There are dull green pigments extractable with 10% KOH.
The perithecia are obvoid or sub-globose, 0.3-0.7 mm diam x 0.5-1.3 mm high. The ostioles are slightly papillate, with an obvious annular (truncatum-type) disc, about 0.2-0.5 mm in diameter.
The ascospores are brown, unicellular, ellipsoid-inequilateral (like a flattened football), with narrowly rounded ends. The measure 14-24 × 4-5.5 µm, with straight, spore-length germ slit on the flattened (less curved) side of the spore. The also have a perispore (clear layer around the spore) that does not dehisce in 10% KOH; both the perispore and the epispore are smooth (no noticeable texture).