A confusing duo: Calocybe cerina and Callistosporium pinicola (Agaricales)

The name <em>Calocybe cerina</em> has recently been applied for two different species of agarics. After studying collections from different European countries it is concluded that the true <em>Calocybe cerina</em> is very close to <em>C. chrysenteron</em> and best regarded as a variety. The new combination <em>Calocybe chrysenteron</em> var. cerina is proposed and a full description of that taxon is given. The majority of collections, identified as <em>C. cerina</em>, appear to belong to a fungus, provisionally described by Bon as <em>Callistosporium luteoolivaceum</em> fo. <em>minor</em>. It is described here as a new species: <em>Callistosporium pinicola. Calocybe juncicola</em> is another species that might be confused with the two species mentioned before and therefore a full description is provided. The status of the genera <em>Rugosomyces</em> and <em>Calocybe</em> is discussed. The new combinations <em>Calocybe obscurata</em> and <em>Calocybe pudica</em> are made.