Griffithsia okiensis sp. nov, is described herein from the material collected in the Oki Islands, Shimane Prefecture. The new species is considered to be unique in the following 3 characters : 1 , the female fertile segment has 1-2 fertile axes ; 2, the female fertile axis consisting of 1-2 axial cells is provided with 3 pericentral cells on the apical cell ; and 3, the procarp has a pair of carpogonial branches arised from the supporting cell.