Several mentions of a saint or saints named Hippolytus occur in the Roman Martyrology. Some must be identified with Hippolytus of Rome, but at least one (a "Greek martyr") cannot possibly be the same person as the Roman presbyter.
The Roman Martyrology includes for 18 August Roman martyrs Hermas, Serapion, and Polyaenus. Ten days later a Roman martyr Hermes and Alexandrian martyrs Polienus and Serapion are commemorated. Perhaps they are the same.