A council of bishops of Byzacena gathered on 24 February 418 in an otherwise unknown place. The council is transmitted in various codices as "Thelense", "Theleptense", "Zelense" and others. The only preserved part of the acts of the council is the letter ("tractatoria") of Pope Siricius, written and accepted at the Council of Rome on 6 January 386 ("Data Roma in concilio episcoporum lxxx sub die viii idus ianuarias post consulatum Arcadi Augusti et Bautonis uu. cc. consulum"), and destined firstly to the bishops of southern Italy. The tractatoria of Siricius was read and accepted at the council of 418 in Byzacena.

The text of the tractatoria of Siricius is also edited as his Letter 5 (CPL 1637, PL 13, 1158-9).