Saints Marcellinus and Peter the Exorcist were martyred in 304. Today is their memorial and we read in the breviary:
The account of the death of these two martyrs, who died in the persecution of Diocletian, comes from Pope Damasus who in turn obtained it from the executioner. The were beheaded in a wood and then buried in the cemetery called The Two Laurels on the Via Labicana. When peace came to the Church a basilica was erected over their tomb.More info here (Wiki entry) and here (Catholic Encyclopedia).