Dolium

Webster's Dictionary

(n.) A genus of large univalve mollusks, including the partridge shell and tun shells.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature

a convenient generic term for the various representations of casks and large vessels which occur frequently in early Christian art, and have svmbolic meaning very generally attributed to them. As they are usually found on tombs, they are taken as empty, representing the body when the soul has fled from it. The close juncture of the staves in some of the casks has been thought to indicate Christian unity.