It cannot be said that all the species of the Phyllodocidæ have yet been satisfactorily defined, much difference of opinion existing as to the separation of varieties and species. In the accompanying key the nomenclature of Professor Mclntosh has been followed, but those Annelids, which are classed by him as varieties, but which have been hitherto generally accepted as distinct species, are shown separately. The true specific value of the arrangement and nature of the papillæ on the proboscis can only be settled by the examination of numerous individuals from various localities; in the meantime it appears best to consider Annelids differing in these particulars as at least varieties worthy of a name.