| Heteroradulum Lloyd ex Spirin & Malysheva, 2017 |
| Heteroradulum adnatum Spirin & Malysheva, 2017 |
| Heteroradulum lividofuscum (Pat.) Spirin & Malysheva, 2017 |
| Hobsonia Berk. ex Massee, 1891 |
| Hobsonia mirabilis (Peck) Linder, 1929 |
| Hyaloraphidium Pascher & Korshikov, 1931 |
| Hyaloraphidium contortum Pascher & Korshikov, 1931 |
| Hyalosynnema Matsush., 1975 |
| Hyalosynnema multiseptatum Matsush., 1975 |
| Hydnogloea Curr., 1871 |
| Hydnogloea gelatinosa (Scop.) Curr. ex Berk., 1873 |
| Hyphodiscosia Lodha & K. R. C. Reddy, 1974 |
| Hyphodiscosia jaipurensis Lodha & K. R. C. Reddy, 1974 |
| Imicles Shoemaker & Hambl., 2001 |
| Imicles aquatica (Cabello, Mengasc. & Aramb.) Shoemaker & Hambl., 2001 |
| Incertae sedis |
| Incertae sedis |
| Incertae sedis |
| Incertae sedis |
| Incertae sedis |