The type species of Licmophora, L. flabellata (Carm.) C. Ag., is atypical for the genus in having a row of intercalary rimoportulae along the sternum and four plate-like plastids with pyrenoids. The pattern of rimoportulae is sufficiently unique to have prompted the question of whether this species should be separated from the genus. We report here L. comnavmaria sp. nov., which also has a row of intercalary rimoportulae. Its plastids are numerous small plates with a pyrenoid, different from plastids in both L. flabellata and other Licmophora species. Like L. flabellata, the new species forms extensive colonies on long, branched, multistranded mucilage stalks. The new species is distinguished from L. flabellata also by the delicate silicification and the extremely fine striae (55 vs 30–35 in 10 µm). Only one other species, L. pfannkucheae Giffen, has been described with intercalary rimoportulae (plastids unknown) and that species may not be distinct from L. flabellata. Thus the present species is a significant addition to the genus.
