Similar to Naetrocymbe punctiformis, but with an extensive dark brown subperidermal hyphal network that extends from the clypeus (involucrellum) which blackens the surrounding bark. Some populations of N. punctiformis have a narrow fringe of dark hyphae surrounding the clypeus, and the two taxa may intergrade. There does not appear to be a link with the tree species involved. As with N. punctiformis, the species does not appear to be lichenized.
Naetrocymbe laburni is an unpublished name, based on Arthopyrenia laburni Leight. ex Arnold (1861).