During the studies of amoebae from the rare and highly productive soil of Chernevaya taiga (West Siberia, Russia) we have found an isolate of a leptomyxid amoeba showing 18s rDNA sequence significantly different from those of other known species of the order Leptomyxida. Here we describe this isolate as a new species, Leptomyxa silvatica n.sp. This species has both morphological and sequence differences from related ones. This finding confirms that reliable morphological differentiation and identification of leptomyxid amoebae is possible only for several remarkable species, while others require molecular data to be correctly labeled or described.