marsupium
From ZooTerms (Dictionary of Invertebrate Zoology)
pouch.
marsupium (noun; Latin marsupium, bag): 1. Brood
2. (Arthropoda: Crustacea) The oostegite in Peracarida, or brood chamber or pouch in others.
3. (Arthropoda: Insecta) In marsupial coccids, a waxen ovisac, longer than the body, filled with eggs that hatch while the insect is still mobile.
5. (Cnidaria: Hydrozoa) In some, the internal pouch borne by the blastostyle.
6. (Echinodermata) a. In some, the cardiac stomach. b. In Viviparous Crinoidea, present on the base of the pinnules adjacent to the gonad and having an external opening; a brood chamber.