Abstract
Bluish Mycena are rare, but constitute a taxonomically complex group. A total of eight bluish species in four sections have previously been reported from North America, Europe, Oceania and Asia. Two species with a blue pileus, collected in China during our taxonomic study of Mycena s.l., are described here as new to science: Mycenacaeruleogrisea sp. nov. and M.caeruleomarginata sp. nov. Detailed descriptions, line drawings and a morphological comparison with closely-related species, especially herbarium specimens of M.subcaerulea from the USA, are provided. The results of Bayesian Inference and Maximum Likelihood phylogenetic analyses of a dataset of 96 nuclear rDNA ITS and 20 nLSU sequences of 43 Mycena species are also presented. The morphological data and the results of the phylogenetic analyses support the introduction of M.caeruleogrisea and M.caeruleomarginata as new species. A taxonomic key to bluish Mycena species of sections Amictae, Cyanocephalae, Sacchariferae and Viscipelles is provided.