Rhizomes branched, rooting at nodes. Leaves 2-7 together on short erect shoots, flattened, linear, 7-17-veined, margin entire or dentate; sheaths auriculate, ligulate. Flowers solitary and terminal. Perianth absent. Male flowers pedunculate; anthers 2; pollen filiform. Female flowers sessile or subsessile; styles divided into 2 filiform stigmas. Fruitlets laterally subcompressed, with bony pericarp, beaked.

An additional species probably in China and so requiring further research is Cymodocea serrulata (R. Brown) Ascherson & Magnus (Sitzungsber. Ges. Naturf. Freunde Berlin, 84. 1870; Caulinia serrulata R. Brown, Prodr. 339. 1810; 齿叶丝粉藻 chi ye si fen zao).

About seven species: tropical to subtropical regions of the E Hemisphere; one species in China.