Eleven species of Tetrastemma are described from the Russian Far East seas. T. tridentatum is nomen dubium. T. papilliformes, T. quasioculata, and T. dilutebasisae belong to the genus Antarctonemertes, T. commensalis belongs to Asteronemertes. Tetrastemma viride Kulikova (= T. kulikovae Gibson, nora invalide) should be transferred to a separate genus. T. bicolor was collected from coastal waters of the Commander Islands and eastern Kamchatka. Prostoma coronatum sensu Yamaoka is redescribed as Tetrastemma pseudocoronatum sp. n. The new species T. appendiculatum, T. olgarum, and T. pimaculatum from Peter the Great Bay (the Sea of Japan) are described. A key to species from the Russian Far East seas is given.
