From Dom Guéranger's The Liturgical Year.
Among the martyrs annually commemorated on this day, the names of Marcellus and Apuleius carry back the mind to apostolic times. They had been disciples of Simon Magus, but were convinced of his lying deceit by the miracles of St. Peter, and shed their blood in testimony of their faith in the true God.
St. Sergius is regarded in the east as one of the most glorious witnesses to our Lord. He suffered in the tenth and last persecution, with his companion St. Bacchus, a soldier like himself of the Roman army in Syria. So illustrious became his sepulchre, that a city sprang up around it, which was called Sergiopolis, and became a metropolitan See. The west soon joined the east in honouring these holy martyrs, and a church was dedicated to them in Rome. Saint-Serge at Angers, founded by Clovis II, testifies to the veneration in which they were held by the Franks.
Prayer
Sanctorum martyrum tuorum nos, Domine, Sergii, Bacchi, Marcelli et Apuleii beata merita prosequantur: et tuo semper faciant amore ferventes. Per Dominum.
May the blessed merits of thy holy martyrs, Sergius, Bacchus, Marcellus, and Apuleius accompany us, O Lord, and make us ever fervent in thy love. Through our Lord.