While performing vegetation surveys in the southern part of the Lena delta, a new species of Carex from section Phacocystis has been found. Morphologically, Carex delongii sp. nov. is most close to C. cespitosa and C. minuta but differs from the former in smaller inflorescences, shorter pistillate spikes, narrow and soft leaves, oblong-ovoid (vs. ovoid) utricles; from the latter, it is distinguished by having smaller spikes and larger utricles. This relationship is also confirmed by molecular data. A detailed description of Carex delongii, its comparison with related species, illustrations, characteristics of habitat and phylogenetic position are reported.
