a Christian martyr of the 6th century, was of pious parentage, and was born probably in 515. When only seven years old he was entrusted by his father, the Roman patrician Tertullus, to the care of St. Benedict of Nursia. Placidus, thus religiously trained, grew up in the service of the Church, and in 541 became abbot of a newly founded monastery at Messina. In 546 he was killed, with his companions, by pirates. He is commemorated in the Church of Rome July 11. See Wetzer u. Welte, Kirchen-Lexikon, vol. 12, s.v.; Alzog, Kirchengesch. 2, 22.