A "chiliarch" [xili/arxos] is literally a leader [a)rxo/s] of one thousand [xilia/s] men; an officer often given command of a garrison, as in e.g. Xenophon, Cyropaedia 8.1.14. But it is also used as the equivalent of the Latin tribunus militum (see LSJ s.v.), and in the present instance actually refers to the tribuni plebis, whose constitutional importance is here dated to the year 315 AUC = 438 BCE. (Eutropius, Breviarium 2.1 has a later dating: 365 years AUC.)