pallium
From ZooTerms (Dictionary of Invertebrate Zoology)
bivalve Mollusca or a Brachiopoda.
pallium (noun; Latin pallium, mantle): 1. The mantle of a
2. (Arthropoda: Insecta) In certain Orthoptera (Caelifera), a membrane from the free margin of the subgenital plate covering the retracted phallus.