The present structure dates probably from the time of Liberius, in the middle of the fourth century. The indefatigable Damasus made a marble pavement—fecit platoniam—and seems to refer to the legend in the following rather unclassical metrical inscription:
HIC HABITASSE PRIVS SANCTOS COGNOSCERE DEBES
NOMINA QVISQVE PETRI PARITER PAVLIQVE REQVIRIS
DISCIPVLOS ORIENS MISIT QVOD SPONTE FATEMVR
SANGVINIS OB MERITVM CHRISTVMQVE PER ASTRA SEQVVTI
AETHERIOS PETIERE SINVS ET REGNA PIORVM
ROMA SVOS POTIVS MERVIT DEFENDERE CIVES
HAEC DAMASVS VESTRAS REFERAT NOVA SIDERA LAVDES.
“Here, you must know, that saints once dwelt. If you ask their
names, they were Peter and Paul. The East sent disciples, as we willingly acknowledge. The saints themselves had, by the merit of their bloodshedding, followed Christ to the stars, and sought the home of heaven and the kingdoms of the blest. Rome, however, obtained to defend her own citizens. These things may Damasus be allowed to record for your praise, O new stars of the heavenly host.”