Definitions of pallium:

noun: cloak or mantle worn by men in ancient Rome
noun: (Roman Catholic Church) vestment consisting of a band encircling the shoulders with two lappets hanging in front and back
noun: (zoology) a protective layer of epidermis in mollusks or brachiopods that secretes a substance forming the shell
noun: the layer of unmyelinated neurons (the gray matter) forming the cortex of the cerebrum