Pope Siricius was the bishop of Rome from December 384 to his death. In response to inquiries from Bishop Himerius of Tarragona, Siricius issued the Directa decretal, containing decrees of baptism, church discipline and other matters. His are the oldest completely preserved papal decretals. He is sometimes said to have been the first bishop of Rome to call himself pope.
Siricius depicted on a medallion
Decretals are letters of a pope that formulate decisions in ecclesiastical law of the Catholic Church.
Breviarium extravagantium by Bernardus Papiensis, the first of the five collections called Compilationes Antiquae.
Collection of the Decretals. Illustration: Boniface VIII and his cardinals