X. The appointment of bishops over too small places is inexpedient and must be discontinued.
That of course which pertains to the priestly dignity we wish to be observed in common with all the statutes of the canons, viz., that bishops be not consecrated in any place nor in any hamlet, nor where they have not been consecrated before; for where the flocks are small and the congregations small, the care of the presbyters may suffice, whereas the episcopal authority ought to preside only over larger flocks and more crowded cities, lest contrary to the divinely-inspired decrees of the holy Fathers the priestly office be assigned over villages and rural estates or obscure and thinly-populated townships, and the position of honour, to which only the more important charges should be given, be held cheap from the very number of these that hold it.
And this bishop Restitutus has reported to have been done in his own diocese, and he has with good reason requested that when the bishops of those places where they ought not to have been ordained die in the natural course, the places themselves should revert to the jurisdiction of the same prelate to whom they formerly belonged and were attached. It is indeed useless for the priestly dignity to be diminished by the superfluous multiplications of the office through the inconsiderate complaisance of the ordainer.
Source: Letters (New Advent)