In the course of the fourth century the city was the chief ecclesiastical centre for the region about the head of the Adriatic, Regio X of the Roman emperor Augustus' eleven regions of Italy, "Venetia et Histria". In 381, St. Valerian appears as Metropolitan bishop of the churches in this territory; his synod of that year, held against the Arians, was attended by 32 (or 24) bishops. Valerian was succeeded by St. Chromatius (388–408), known for his homiletic and exegetical works. He promoted the work of Sts. Jerome and Rufinus and kept contact with Sts. Ambrose of Milan and John Chrysostom.