From the martyrology (for August 6):
"At Rome, on the Appian Way, in the cemetery of Callistus, the birthday of blessed Sixtus II, pope and martyr, who received the crown of martyrdom in the persecution of Valerian by being put to the sword. Also, the holy martyrs Felicissimus and Agapitus, deacons of blessed Sixtus; Januarius, Magnus, Vincent, and Stephen, subdeacons, all of whom were beheaded with him and buried in the cemetery of Praetextatus. With them suffered also blessed Quartus, as is related by St. Cyprian."