Five new species of the genus Polymeridium are described from Brazil. All exhibit at least one character that was previously unknown in the genus: P. corticatum has a corticate thallus and 2 ascospores per ascus, P. immersum has the ascomata deeply immersed in the bark under the thallus, P. isohypocrellinum has a red, KOH+ green pigment (iso-hypocrellin) in the ostiole, P. julelloides has short and broad muriform (Julella-like) ascospores, and P. paraproponens has ascomata in groups of two to three. Brazil is clearly the centre of diversity of the genus. Iso-hypocrellin is a new substance for the genus.

Twenty-three species of Pyrenula from Latin America are treated here. Several species show characters that were not previously reported in the genus and are rare or new to lichenized fungi, viz. yellow, orange or red (KOH+ green) oil inspersion in the hymenium, yellow oil in young ascospores or longitudinal ridges on the ascospore wall. Two taxonomically significant types of over-mature spores are illustrated. The following new species are described: Pyrenula aggregataspistea Aptroot & M. Cáceres, P. aurantioinspersa Aptroot & Sipman, P. cornutispora Aptroot & M. Cáceres, P. flavoinspersa Aptroot & Sipman, P. guyanensis Sipman & Aptroot, P. infraleucotrypa Aptroot & M. Cáceres, P. inframamillana Aptroot & M. Cáceres, P. infrastroidea Aptroot & Sipman, P. maritima Sipman & Aptroot, P. mattickiana Sipman & Aptroot, P. minoides Aptroot & Sipman, P. monospora Aptroot & Sipman, P. paraminarum Aptroot & M. Cáceres, P. perfecta Aptroot & Sipman, P. plicata Sipman & Aptroot, P. rubroinspersa Aptroot & Sipman, P. rubronitidula Aptroot & M. Cáceres, P. rubrostigma Aptroot & M. Cáceres, P. tetraspora Aptroot & Sipman, P. triangularis Aptroot & Sipman, P. viridipyrgilla Aptroot & M. Cáceres. Pyrenula seminuda (Müll. Arg.) Sipman & Aptroot is a new combination.