A locket containing an amulet or charm to ward off evil and protect a young Ancient Roman boy from harm. The bulla is first placed around the boy's neck soon after birth, and is worn until the boy comes of age. When he does come of age, he shaves off the beginings of his first beard, and dedicates them, and the bulla, to the household gods. Only the boys got bullas. (Ecce Romani I, Prentice Hall, page 17)
Marcus took off his bulla, and set it down on the small shrine to the household Gods.