PRAEFECTUS URBI, praefect or warden of the city, was originally
called _Custos Urbis_. The name _praefectus urbi_ does not seem to
have been used till after the time of the decemvirs. The dignity of
_custos urbis_, being combined with that of _princeps senatus_, was
conferred by the king, as he had to appoint one of the decem primi as
princeps senatus. The functions of the _custos urbis_, however, were
not exercised except in the absence of the king from Rome; and then
he acted as the representative of the king: he convoked the senate,
held the comitia, if necessary, and on any emergency, might take
such measures as he thought proper; in short, he had the imperium in
the city. During the kingly period, the office of _custos urbis_ was
probably for life. Under the republic, the office, and its name of
_custos urbis_, remained unaltered; but in B.C. 487 it was elevated
into a magistracy, to be bestowed by election. The _custos urbis_
was, in all probability, elected by the curiae. Persons of consular
rank were alone eligible. In the early period of the republic the
_custos urbis_ exercised within the city all the powers of the
consuls, if they were absent: he convoked the senate, held the
comitia, and, in times of war, even levied civic legions, which were
commanded by him. When the office of praetor urbanus was instituted,
the wardenship of the city was swallowed up in it; but as the Romans
were at all times averse to dropping altogether any of their old
institutions, a praefectus urbi, though a mere shadow of the former
office, was henceforth appointed every year, only for the time that
the consuls were absent from Rome for the purpose of celebrating the
Feriae Latinae. This praefectus had neither the power of convoking
the senate nor the right of speaking in it; in most cases he was a
person below the senatorial age, and was not appointed by the people,
but by the consuls. An office very different from this, though
bearing the same name, was instituted by Augustus on the suggestion
of Maecenas. This new praefectus urbi was a regular and permanent
magistrate, whom Augustus invested with all the powers necessary to
maintain peace and order in the city. He had the superintendence of
butchers, bankers, guardians, theatres, &c.; and to enable him to
exercise his power, he had distributed throughout the city a number
of milites stationarii, whom we may compare to a modern police. His
jurisdiction, however, became gradually extended; and as the powers
of the ancient republican praefectus urbi had been swallowed up by
the office of the praetor urbanus, so now the power of the praetor
urbanus was gradually absorbed by that of the praefectus urbi; and at
last there was no appeal from his sentence, except to the person of
the princeps himself, while any body might appeal from the sentence
of any other city magistrate, and, at a later period, even from that
of a governor of a province, to the tribunal of the praefectus urbi.