Species of the genus Galaxaura are unusual in having gametophyte and tetrasporophyte phases that, while somewhat similar in stature, display markedly different cortical morphologies.These differences have, in the past, led to many species being erected that represent no more than life-history phases of a single species. This paper discusses the identity of the tetrasporophyte phase of G. rugosa, the type of the genus, and concludes that it, at least, includes G. subverticillata, a species regarded as independent in several recent publications. Evidence for this conclusion resides in a comparison of large subunit rDNA sequence data from G. rugosa and “G. subverticillata” collected in Hawaii, in situ observations, plus a review of historical and recent morphological studies. In addition, evidence is presented to support the inclusion of plants with both flattened and subterete branch morphologies in Dichotomaria marginata (Ellis et Solander) Lamarck.