PLATONIA. — From *platona* or *platomum*: a slab of marble.
The term is found used in the *Liber Pontificalis*, in the biography of Liberius, of whom it is said that he «ornavit de platonis marmoreis sepulcrum sanctae Agnetis» (Lib. Pont., I, p. 208); in the biography of Pope Damasus, who dedicated a «platomam in catacumbas» (ibid., I, pp. cv and 214, nn. 9 and 10); in the biography of Sixtus III it is said that he clad with «platomas» of porphyry the enclosure around the tomb of St. Lawrence and placed in the cemetery of Callistus a «platomam» to record the names of the bishops buried there. This slab was reconstructed by G. B. De Rossi (Roma sotterr., II, Roma 1867, pp. 33 ff.) using the laterculus transcribed in the *Turonense* collection (id., Inscr. Christ., II, 1888, p. 66, n. 25 a). In the Middle Ages the apostolic memorial «in catacumbas» was gradually localized to the west of the Basilica itself and this mausoleum, erected by the Prefect of Rome Vincent, a friend and supporter of Damasus, where later the martyr Quirinus, Bishop of Siscia, was buried, came to be called *p.*