| Name | Antithamnion cruciatum var. radicans (J. Agardh) Collins |
| Authorship | (J. Agardh) Collins |
| Rank | Variety |
| Placed in | Antithamnion cruciatum (C. Agardh) Nägeli |
| Holdings | 2 Specimens held in the Harvard University Herbaria identified as Antithamnion cruciatum var. radicans (J. Agardh) Collins |
| Identification made in | [no date] (2) |