Latin diminutive of locus, "place"; a small grave or chamber cut out of the rock sides of a gallery, usually in a catacomb. Loculus is the term used to distinguish a small individual grave from the larger and more imposing ones, called arcosolia, which were large enough to receive a coffin or sarcophagus. The loculus was a horizontal niche scooped out of the soft rock of the tunnels running through the catacombs. In Roman law, all cemeteries and burial places were certified as loci religiosi and, like churches and temples, were inviolable. The term loculus, thus, came to be applied to any small grave sacred to the dead. The term was also applied to the small cavity prepared in an altar stone to receive the relics of martyrs as required for the celebration of Mass. The term sepulcher is also used for loculus in this sense.
Bibliography: h. leclercq, Dictionnaire d'archéologie chrétienne et de liturgie (Paris 1934–43) 9.2. e. diehl, Inscriptiones Christianae latinae veteres, 3 v. (Berlin 1925–31) 222–232.
[e. e. malone]