Nomenclature of the seagrass Halophila baillonis Ascherson

The name Halophila baillonis Asch. was published by J.D. Hooker based on Ascherson's comment on Moseley's Halophila collection from St. Thomas. Ascherson's subsequent species descriptions under either H. baillonii or H. baillonis referred to Hahn's collection from Martinique and the Holm's publication; both of these are now known to belong to H. decipiens Ostenf., not to H. baillonis. Because den Hartog selected the Moseley specimen at the Kew Herbarium as the lectotype of H. baillonis the names H. baillonii or H. baillonis as used in all of Ascherson's post-1874 publications are synonyms of H. decipiens. The correct nomenclature of the species based on the Mosley collection should be H. baillonis Asch. in Hook. f. which is abbreviated as H. baillonis Asch.; it is not to be treated as an orthographic error for H. baillonii. The species should not be cited as either H. baillonis Asch. ex Hook. f. or as H. baillonis Asch. ex Dickie in Hook. f. More importantly, the illegitimate name H. baillonii Asch. is considered to refer to a different species, H. decipiens.