Critical reinvestigation of the four presently recognised species of the green macroalgal genus Chamaedoris (C. auriculata, C. delphinii, C. peniculum and C. orientalis) based on morphological and molecular data reveals that at least one species, C. orientalis, is actually a member of the genus Struvea and is herein transferred to that genus as S. okamurae nom. nov. This has also necessitated a revised circumscription of the genus Struvea. Morphological features traditionally used to delimit the three other species of Chamaedoris (shape of capitulum and number of cells split off from the distal pole of the stipe) are not diagnostic, and the traditional species delineations need to be reassessed. Detailed morphological and morphometric analyses reveal that more subtle differences exist among the three species, including cell dimensions and crystalline cell inclusions. Observations and molecular phylogenetic analyses of new collections over the past 27 years allow us to update knowledge of their biogeographic distributions and determine their relationships with species of the closely related genera Apjohnia, Boodlea, Cladophoropsis, Phyllodictyon and Struvea
