A revision of the genus Orchestia Leach, 1814 with the reinstatement of O. inaequalipes (K.H. Barnard, 1951), the designation of a neotype for Orchestia gammarellus (Pallas, 1776) and the description of three new species (Crustacea: Amphipoda: Talitridae: Talitrinae)

The amphipod genus Orchestia is revised. It now includes 10 species of which three are new: O. forchuensis sp. nov. from north-eastern North America and Iceland., O. perezi sp. nov. from Chile and O. tabladoi sp. nov. from Argentina. Orchestia inaequalipes (K.H. Barnard 1951) is reinstated. The type species of the genus, O. gammarellus is redescribed based on material from Fountainstown, Ireland and a neotype is established to stabilize the species. The species was originally described from a garden in Leiden, far from the sea. Its true identity is unknown and no type material exists. Orchestia gammarellus (Pallas, 1776) is shown to be a sibling species group with members in both hemispheres of the temperate Atlantic as well along the Pacific coast of South America. A hypothesis for the establishment of the current distribution of Orchestia species is presented that extends back to the Cretaceous.