Xanthagaricus caeruleus, a new species with ink-blue lamellae from southeast China

Xanthagaricus caeruleus, a new species of Agaricaceae from southeast China is described and illustrated. It is characterized by its small basidiomata with a pileus covered by grayish lilac to grayish violet squamules, pallid white lamellae when young becoming pastel blue to ink-blue or blackish blue with age, greenish gray to grayish brown basidiospores, and epithelial pileipellis which is composed of agglutinated globose to subglobose, rarely clavate to ellipsoidal thin-walled cells. Phylogenetic analysis showed that the new species is unique and distinct from other known species within the genus Xanthagaricus. Detailed description, color photos and illustrations of the new species are presented.