| Name | Porphyra umbilicalis f. linearis (Greville) Rosenvinge |
| Authorship | (Greville) Rosenvinge |
| Rank | Forma |
| Placed in | Porphyra umbilicalis Kützing |
| Holdings | 1 Specimen held in the Harvard University Herbaria identified as Porphyra umbilicalis f. linearis (Greville) Rosenvinge |
| Identification made in | [no date] (1) |