Among the materials with which De Rossi worked may be cited: Acta Martyrum of S. Jerome, Liber Pontificalis, the “Pilgrim Itineraries,” and the “Monza” Catalogue, which is specially described--Decoration of certain crypts--Basilica (ruins) above ground--Luminaria--Graffiti of pilgrims--Inscriptions of Pope Damasus _in situ_, and also preserved in ancient syllogæ 226 Certain of his more important discoveries in the cemeteries of SS. Domitilla, Priscilla, Callistus--The yet later discoveries of Marucchi and others 230 III GENERAL ACCOUNT OF THE VASTNESS AND SITUATION OF THE CATACOMBS (1) The Vatican cemetery and the groups of catacombs on the right bank of the Tiber 232 IV (2) On the Via Ostiensis--Basilica of S. Paul--Cemeteries on the Via Ardeatina--Grandeur of cemetery of S. Domitilla--The small basilica of S. Petronilla 236 V (3) Groups of cemeteries on the Via Appia--S. Sebastian (_ad Catacumbas_)--Group of S. Callistus--The Papal crypt--S. Soteris--Catacomb of Prætextatus on left hand of the Via Appia--Tomb of S. Januarius in this catacomb 242 VI (4) Cemeteries on the Via Latina and Via Tiburtina--S. Hippolytus--S. Laurence--S. Agnes’ cemetery on the Via Nomentana 248 VII (5) Cemeteries on the Via Salaria Nova--S. Felicitas; the great cemetery of S. Priscilla, and the ancient Roman churches connected with it--Legends--Remains of basilica of S. Sylvester over the cemetery of S. Priscilla--Memories of S. Peter in this cemetery--Its waters--Recent discoveries--Popes buried in the basilica of S. Sylvester 258 VIII (6) Unimportant cemeteries on the Via Salaria Vetus--S. Pamphylus--S. Hermes--S. Valentinus, etc. 274 APPENDIX I.--S. PETRONILLA Suggested derivation of Petronilla--De Rossi and other scholars still hold to the ancient Petrine tradition--Reasons for maintaining it--Early mediæval testimony here--Traces of the early cult of this Saint 277 APPENDIX II.--TOMB OF S. PETER Probable situation of the tomb in present basilica of S. Peter--Account of what was found in the course of the excavations in the seventeenth century, by Ubaldi, Canon of S. Peter’s, who was an eye-witness of the discoveries made in A.D. 1626, when the works required for the great bronze Baldacchino of Bernini were being carried out 279 PART II