Streptophyllopsis kuroshioensis (SEGAWA) gen. et comb. nov. is described herein on the basis of the detailed observations on the abundant materials collected from deep-waters in the Oki Islands, Shimane Prefecture, in the past seven years since 1974. The frond of the new taxon has a shortly stipitate simple annual blade arising singly from each terminal of the dichotomously branched perennial prostrate branch which has perennial haptera on its ventral surface. Mucilage-canals are present in the blade, stipe and the prostrate branch. Sporangial sori are formed on both surfaces of the blade and the stipe. The paraphysis has a short mucilaginous appendage.