Typification of Agaricus cespitosus, Ag. oniscus, and Ag. sphagnicola and their synonymy with Lichenomphalia umbellifera

Protologue descriptions and original material of Agaricus cespitosus, Ag. oniscus, and Ag. sphagnicola were studied to determine the intended species concept for each. Agaricus cespitosus fits the second most common presentation of the current Lichenomphalia umbellifera and is placed in synonymy with it. Agaricus oniscus was created as a synonym of Ag. cespitosus, confirmed by its original material; therefore, it is also placed in synonymy with L. umbellifera, resolving problems noted with past attempts trying to apply the epithet to darker sphagnicolous species of Arrhenia. Careful analysis of the protologue for Ag. sphagnicola revealed a good fit with L. umbellifera but serious conflict if applied to species of sphagnicolous Arrhenia ; it was, therefore, also synonymized with L. umbellifera. Agaricus cespitosus and Ag. oniscus are lectotypified with illustrations from their original material, Ag. oniscus is epitypified with a modern sequenced collection from Sweden, and Ag. sphagnicola neotypified with a K collection made by Berkeley, both identified as L. umbellifera.