Historians of late Roman Christianity, especially those of a Gibbonian stripe, take delight from this extraordinary account of the no-holds-barred contest for the papacy in 366, and the resulting massacre in the Liberian basilica of the supporters of Ursinus. But they rarely take heed of their source. The text stands at the opening of the Collectio Avellana, a mid-sixth-century collection of nearly 250 documents relating to the bishopric of Rome in the fourth, fifth, and sixth centuries. While its account of Damasus is frequently cited, the Collectio as a whole is something of a backwater, in both medieval and modern scholarship. This obscurity is surely undeserved, and it obtains only because we have asked the wrong question. As an early medieval canon law collection the Collectio is indeed a virtual dead end – far less successful and important than the near-contemporary collection of Dionysius Exiguus.