Canon CXXIII.
Canons of Local Councils Received in Trullo (Sardica, Carthage) · The Seven Holy Ecumenical Councils
If in the mother cathedrals a bishop should have been negligent against the heretics, let a meeting be held of the neighbouring diligent bishops, and let his negligence be pointed out to him, so that he can have no excuse. But if within six months after this meeting, if an execution was in his own province, and he had taken no care to convert them to Catholic unity, no one shall communicate with him till he does his duty. But if no executor shall have come to the places, then the fault shall not be laid to the bishop.
LocalT 2.127.3
A bishop who spurns the care of heretics, and if after being warned he continues for six months in his contempt, and has no care for their conversion, is to be excommunicated.
LocalT 2.127.6
So [i.e. “Metropoles”] I turn matrices cathedræ. I know indeed there were no fixed ecclesiastical metropoles, in Africa; but they had civil metropoles called by that name, can. 86, (89) which see.
LocalT 2.127.9