[Illustration: SEPVLCRVM FLAVIORVM] "the tomb of the Flavian family," namely, of those relatives of Domitilla who had embraced the Christian faith. Under the pavement of the nave, aisles, and presbytery, are numberless graves, some of which belong to the original catacombs, before they were cut and disarranged by the building of the basilica; others are built in accordance with the architectural lines of the basilica itself. A grave belonging to the first series, that is, to a gallery of the catacombs which had been blocked by the foundations of the left aisle, bears the date of the year 390; while a sarcophagus placed at the foot of the altar is dated Monday, May 12, 395. It is evident, therefore, that the basilica was built between 390 and 395, during the pontificate of Siricius. No memorial of Petronilla, the third saint for whom the building was named, has been found within the sacred enclosure,--a fact not wholly unexpected, because the coffin in which her remains were placed is known to have been removed to the Vatican by Paul I. (755-756), at the request of the king of France. In November, 1875, a cubiculum was found at the back of the apse, connected with it by a corridor which opens near the episcopal chair. The walls of this passage are covered with _graffiti_ and other records of pilgrims. The cubiculum contains two graves: one empty, in the arcosolium, the place of honor; the other, in front of it, of a much later date. The front of the arcosolium is closed by a wall, on the surface of which is an interesting fresco, which is here reproduced. [Illustration: Petronilla and Veneranda.] The younger figure, on the right, is Petronilla Martyr; the elder is a matron named Veneranda, buried January 7 (DEP_osita_ VI. IDVS. IANVARIAS), in the sarcophagus below the picture. There is no doubt that Petronilla was buried in close proximity to this cubiculum. The story of her relationship to S. Peter has no foundation whatever; it rests on an etymological mistake, by which the name Petronilla is treated as a diminutive of Petrus, as is Plautilla of Plautius or Plautia, and Domitilla of Domitius or Domitia. Petrus is not a Latin name; it came into use with the spreading of the gospel, and only in rare and exceptional cases. The young martyr was named after a member of the same Flavian family to which this cemetery belonged, Titus Flavius Petron, an uncle of Vespasian. Her kinship with the apostle must consequently be taken in a spiritual sense. Towards the end of 1881 another remarkable discovery took place in these catacombs: that of a cubiculum which in style of decoration is unique. It looks more like the room of a Pompeian house than a Christian crypt. Its architectural paintings with groups of frail columns supporting fantastic friezes, and enclosing pastoral landscapes, might be compared to the frescoes of the Golden House of Nero, or those of the house of Germanicus on the Palatine; but they find no parallel in "subterranean Rome."