Of the eleven thousand extant inscriptions only thirteen hundred and seventy-four bear dates. The period of the others can be only approximately determined by a comparison with those whose ages are known; by a careful examination of the execution, language, and general sentiment, those of earlier date being less florid and more classical in style; by the presence or absence of certain symbols, as the sacred monogram, of which no example is known before the period of Constantine; and by the position in the Catacombs, those in the lower _piani_ being of later date. Judging by these criteria, De Rossi has arrived at the following conclusions: About six thousand of the epitaphs belong to the first four centuries, and are from the Catacombs; the rest were found above ground. Of these six thousand, about four thousand are before the year 324 A. D., when Constantine became sole emperor. Only one of the _dated_ inscriptions belongs to the first century, (A. D. 71,) two are of the second, (A. D. 107 and 111,) and 409 twenty-three of the third; the fourth century is represented by over five hundred; the fifth by nearly as many; the sixth by about three hundred, principally in its earlier half; and the seventh by only seven. Of these dated inscriptions, all before the year 313 A. D., when the edict of Milan gave peace to the church, are from the Catacombs. After that event subterranean sepulture rapidly decreased. Of the epitaphs bearing dates between the years 313 A. D. and 337 A. D., two thirds are from the Catacombs, and one third from the basilicas and other places of burial above ground. From A. D. 337 to the time of Julian the proportion of each was about equal. Of the dated inscriptions of the last quarter of this century, about one fourth are subterranean. Of those between the years A. D. 400 and A. D. 410, not one in ten is from the Catacombs, and after that period not one subterranean example occurs.[680] Sometimes, in epitaphs of late date, the name of the church and the position of the tomb are mentioned, as in the following: DEPOSITVS IN BASILICA SANCTORVM NASARI ET NABORIS SECVNDV ARCV IVXTA FENESTRA, (A. D. 404,)--“Buried in the basilica of Sts. Nasarius and Nabor, in the second arch near the window;” DEPOSITA IN CONTRA COLONNA VII, (A. D. 452,)--“Buried in the space opposite the seventh column.” The Christian era was not adopted as a note of time till after the sixth century. The dates of the Roman inscriptions were therefore indicated by the names of the consuls for the year, generally written in an abbreviated form.[681] Frequently the addition VC., for _Vir 410 Clarissimus_--“An illustrious man”--or, in the case of imperial consuls, DN., for _Dominus Noster_--“Our Lord”--also occurs.[682] In one instance the epithet DIVVS--“Divine”--assumed by the emperors, is employed in a Christian epitaph, in unthinking imitation of a heathen formula.