We compared the morphology of all four members of Pelvetia and Silvetia (Fucaceae, Phaeophyta), with an emphasis on phylogenetic relationships. Silvetia is segregated from Pelvetia because it has two, longitudinally divided eggs in the oogonium. In contrast, the eggs of the genus Pelvetia are transversally divided. A cladistic analysis, based on 17 morphological features, shows that Pelvetia is closely related to Hesperophycus and Pelvetiopsis, as are three species of Silvetia. We ran infer from the cladistic tree and biogeographic information that some silvetian ancestor populations from the northern Pacific region likely evolved to S. babingtonii in northern Japan and then moved to Korea and California (USA), where S. siliquosa and S. compressa, respectively, diverged. Our morphological study corroborates the DNA-based phylogeny and the ensuing taxonomy for the two genera. These results demonstrate the necessity for systematically revising the family Fucaceae to emphasize egg development, rather than egg number in the oogonlum, as a diagnostic character.