Mostaganem corresponds to the ancient Punic port of Murustaga. After becoming part of the Roman Empire, it was, according to some sources, officially renamed Cartennae under the emperor Gallienus (253–268). However, according to more weighty sources, Cartennae (or Cartenna or Cartennas) corresponds instead to modern Ténès, 50 km to the east. In any case, Murustaga is the name by which the town was known when it became a Christian bishopric, and by which it is referred to in the Catholic Church's list of episcopal sees. It also underlies the modern name of Mostaganem.