one and a quarter miles from the Porta S. Sebastiana (Porta Appia).
It is composed of several groups of cemeteries of different periods from the first century to the fourth. These groups are so united by corridors that they may be considered as one vast catacomb. The Cemetery of Callistus in part dates from the first century, but it only obtained the designation of "Callistus" in the last years of the second or in the first years of the third century, when Callistus the deacon was appointed by Zephyrinus the Bishop of Rome as superintendent of The Cemetery. Subsequently Callistus succeeded Zephyrinus as bishop, and greatly enlarged the original area, one chamber of which he set apart as the official burying-place of the bishops or popes of Rome. Before the time of Callistus the official burying-place of the bishops was the cemetery on the Vatican Hill, immediately contiguous to the sepulchre of S. Peter. At the end of the second century the limited space on the Vatican Hill was completely occupied—hence the necessity for arranging a new papal crypt.
The oldest portion of the "Callistus" group is the so-called Crypt of Lucina (first and second century). It was evidently in the first instance excavated in the property of the noble family of the Cæcilii, and was used as the burying-place of Christian members of that great House. De Rossi believes that the "Lucina" in whose land the crypt was originally arranged was no other than the well-known Pomponia Græcina, wife of Plautius, the famous general in the days of Nero, whose conversion to Christianity about the year of grace 58 is alluded to in scarcely veiled language by Tacitus. If this be the case, the name "Lucina" was assumed by the great lady in question, and by which she was generally known in Christian circles. The assuming of such an "agnomen" was not uncommon among Roman ladies. The original area of the Cemetery of Lucina was greatly enlarged in the days of the Emperor Marcus and in the last years of the second century. The chapel of the popes, above alluded to, and other important funereal chambers, are included in this enlarged area.
It was in the course of the third century, no doubt after the construction of the new crypt or chapel of the
