| Family | Scientific Name | Common Name | Habitat | Distribution | Image |
|---|---|---|---|---|---|
| Cymodoceaceae | Ruppia cirrhosa | Spiral Ditch-grass; Widgeongrass | Lakes. | Wisconsin west to Alaska, south to Louisiana, Texas, New Mexico, Arizona, California, and Mexico; Central America, South America; Eurasia. |  (c) Keith, Eric - CC-BY-NC, permission granted to NCBG |
| Cymodoceaceae | Ruppia maritima | Widgeon-grass, Ditch-grass | Brackish estuaries, rivers, marsh pools. | Nearly cosmopolitan. |  (c) Bradley, Keith |