On the first day of the Conference, the Donatists challenged the list of the signatures of the Catholic bishops on the document in which they had assigned their representatives. A roll call followed, in which the tribune Marcellinus, who presided, called the Catholic bishops one by one, and their Donatist counterparts were to identify them.

In this case, there was no Donatist bishop at Usula, but only a presbyter. S. Lancel suggests in his note that either the see was temporarily vacant, or there were no Donatist bishops there at all, and a presbyter from a neighbouring see ministered to the faithful.