The genus Skyttea is characterized by urceolate ascomata, with a narrow pore when young, a greenish or brownish, rarely reddish exciple of conglutinate hyphae with subglobose to ± cylindrical lumina, bordered near the margin by hyaline to greenish or brownish, usually smooth, straight hairs, the absence of periphyses, rarely branched and apically hardly thickened paraphyses, asci and a hymenium that are entirely I — and KI —, a thin lateral and a very thick apical ascus wall with a small ocular chamber, and normally aseptate ascospores. It is considered to belong to the Leotiales and not to the Ostropales. It comprises at least 17 species, including S. caesii sp. nov., S. carboneae sp. nov., S. lecanorae sp. nov., S. mayrhoferi sp. nov., S. pyrenulae sp. nov., S. radiatilis comb, nov., S. tavaresae. sp. nov. and S. thelotrematis sp. nov. Rhymbocarpus is shown to be a distinct leotialean genus, distinguished from Llimoniella by a different excipular structure, different pigments and the presence of excipular hairs, which, in some species, are embedded in the excipular gel and thus not visible macroscopically. In addition to the type species, R. geographici, of which a neotype is designated, it includes R. boomii sp. nov.,R. cruciatus comb, nov., R. fuscoatrae comb, nov.,R. makarovae sp. nov.,R. neglectus comb, nov., R. pertusariae sp. nov.,R. pubescens comb. nov. and R. stereocaulorum comb. nov. Llimoniella s. str. comprises at least 6 species, including the type, L. scabridula, L. adnata, L. pertusariae sp. nov., L. pyrenulae sp. nov., L. ramalinae comb. nov. and L. vinosa comb. nov. Several species formerly assigned to Skyttea or Llimoniella are now included in the leotialean genus Unguiculariopsis, and the following new combinations are proposed: Unguiculariopsis acrocordiae comb, nov., U. groenlandiae comb. nov. and U. lesdainii comb. nov. A lectotype is chosen for Lichen stictoceros, which is shown to be a synonym of Evemia prunastri. Keys are given for the species of Skyttea, Llimoniella and Rhymbocarpus, and for the lichenicolous genera of Leotiales and Ostropales.