Gallia Lugdunensis
The Cotentin, conquered by Quintus Titurius Sabinus in 56 BC, was divided between the "pagus constantiensis" ("County of Coutances") and the "pagus coriovallensis" ("County of Coriallo"), within Gallia Lugdunensis. Coriallo housed a small garrison and a castrum was built on the left bank of the Divette as an element of the "Litus saxonicum", after Saxon raids at the beginning of the 4th century.