Eurythenes gryllus is redescribed based on the holotype of Gammarus gryllus Lichtenstein in Mandt, 1822; the holotype of Lysianassa magellanica H. Milne Edwards, 1848; and one of the specimens used by Lilljeborg (1865a) when establishing the genus Eurythenes. Eurythenes obesus (Chevreux, 1905), is redescribed and a neotype is established. New material of E. gryllus and E. obesus is recorded from Australasian waters. Eurythenes thurstoni n. sp. is described and Eurytheneidae n. fam. is established for this genus within the Lysianassoidea.
Crustacea, Amphipoda, Eurytheneidae n. fam., Eurythenes, deep-sea, new family, new species.