Illustrated catalogue of types of species historically assigned to Lessonia (Laminariales, Phaeophyceae) preserved at PC, including a taxonomic study of three South-American species with a description of L. searlesiana sp. nov. and a ne...

Specimens of Lessonia from Fuegia and types housed at PC, as well as specimens from Kerguelen Islands were examined with special reference to anatomical features. When separating L. flavicans from L. vadosa (Searles, 1978), the name L. flavicans had been assigned to a deep water species without cortical lacunae because the lacunae present in Bory de Saint-Vincent's type material had been overlooked. Actually, lacunae of the cortex are present in type material of both L. flavicans Bory de Saint-Vincent in Dumont d'Urville and L. vadosa Searles. On this basis and considering the other morphological features as well, Bory's type material corresponds actually to the species currently named L. vadosa and not to the one named L. flavicans. L. vadosa becomes thus a taxonomic synonym of L. flavicans and L. flavicans sensu Searles (1978) has no name anymore; the new species L. searlesiana is thus proposed for it and a holotype is designated among Searles' original material. Furthermore, the specimen previously designated as the lectotype of L. flavicans among the material collected during the Coquille expedition was actually not eligible as possible syntype and a new lectotype is therefore designated here. Type material of taxa historically assigned to the genus Lessonia and preserved at PC is illustrated.