A taxonomic revision helps to clarify differences between the Atlantic invasive and the Mediterranean endemic (Crustacea, Amphipoda).

(formerly ), described by Arresti (1989), can be considered to be a synonym of west-Atlantic (Stimpson, 1853), based on morphological observations of paratypes and specimens recently collected in the type locality of . The first collections of , from the eastern Atlantic were from the port of Rotterdam (The Netherlands) in 2009 and later in Wimereux, Opal Coast (France) in 2014; however, the synonymy of with backdates to the first European record of in 1985 at La Vigne, Bay of Arcachon (France). This indicates that has been established along European Atlantic coast for many years. An assessment of the nominal valid species belonging to the genus was carried out and a comparison between the Atlantic and the very similar Mediterranean hyalid species, , is presented based on morphological features and distribution. Due to the invasive ability of , a comparison between the two species is necessary.