Carapace very large, membranous. No pleural plate on abdominal somites.
Antennal scale with 2 segments. Endopods of 2nd to 4th pereopods relatively short, developed as gnathopods; those of 5th to 7th very long, slender, subchelate; that of 8th normal. Exopod of uropods with distal suture.
Only one genus, Eucopia, whose species are poorly defined and difficult to distinguish. Eucopia is most common below 1000 m in the World Ocean. Body and appendages red.