opossum shrimp

from The Century Dictionary.

• noun A schizopodous crustacean or shrimp of the family Mysidæ: so called because the females carry their eggs in pouches between the thoracic legs. See Mysis.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun shrimp-like crustaceans whose females carry eggs and young in a pouch between the legs