Saint Marcellinus was a priest and Saint Peter an exorcist (one of the minor orders), who both lived in Rome and laboured there under the cruel Emperor Diocletian. They were martyred together. So great was the veneration of the Catholics for them that a basilica was built over their tomb in Rome. Their names are mentioned in the Roman Canon of the Mass.
If “the law of praying is the law of believing,” we may know from this simple recognition how great and heroic these two martyrs were, and how much they should be remembered and invoked.