Key to the species of Chaetomorpha
| 1 | Filaments with distinct basal cell. longer (to 9 mm) than cells above; filaments mostly more than 400 µm wide | C. antennina |
| 1 | Filaments attached or free-floating in tufts or strands, basal cell, if present less than 1 mm long | 2 |
| 2 | Cells in upper portion 250 - 600 µm diam., tending to be isodiametric | C. aerea |
| 2 | Cells mostly (65) 80 - 100 µm diam., tending to be longer than wide | C. capillaris |