At left is a 5th century fresco in what is now the bookstore of St. Paul Outside the Walls, Rome. As the inscription at the bottom shows, the female saint on the left is St. Marcianilla and the one on the right is St. Basilissa. The boy with the halo is St. Celsus, son of St. Marcianilla. (His inscription reads, "S[ANCTUS] CELS[US] PVER" -- St. Celsus the Boy.) Mother and son were martyred in Egypt on the same day during the persecution of Diocletian, along with St. Julian, the husband of St. Basilissa.
Basilissa's husband is called St. Julian the Hospitaller in Butler's Lives of the Saints but is not the same person as the hospitable St. Julian of medieval legend. In the story Butler relates, the husband and wife pledged themselves to chastity in marriage and devoted all their energies to caring for the sick and the poor in their home, whence the epithet "hospitaller."
Feast day: January 9
A separate image of Basilissa:
Menu6th-century mosaic in Croatia