OSTIA, os'-fi-a, a town built by King Ancus Martins at the mouth of the Tiber, sixteen miles by land from Rome, of which it became the port ; it also rose to importance from its salt-works.
OsTaacismos, os-trri-cis'-mos, a peculiar mode of exile introduced at Athens by Clisthe'nes, sto n.c., and intended to enable the government to order out of the country for ten (afterwards five) years, without any special accusation or trial, any individual who was considered from his power or designs to be dangerous to it. This exile carried with it no other punishment ; the octracised person re tained his property, and at the end of the period, or before, if the vote were annulled, resumed all his political rights and duties. To guard against its abuse, the Ostracism was surrounded with formalities ; the Senate and Assembly had to determine whether the step was necessary, and if so. a day was fixed for the voting, which was made by means of oyster-shells (jorporni), and at least 6,000 votes had to be recorded against a person before he could be ordered to withdraw. The Ostra cism was practised in several other demo cratical Greek states, and was called Pita/is sues (from rri:roxoo). It must be particularly noticed that Ostracism was a precautionary measure, not a punishment. In all the Greek states voluntary exile (4n7,() was common for homicide, sentence being then passed : and the frequent changes of government and the violent antagonism of the oligarchs and demo.
crats led to frequent expulsions of one party, or a portion of it, by the other : so that from nearly every state there was always a body of exiles (o7 or o7 oe6voi-tec, called ui on their return).—The ancient Roman republican form of banishment was the iiquce et iglu's interdictio within the city, or, later, within a certain distance from it, a ban pronounced by the people or a magistrate on any offender, who was thus cut off from the first necessaries of life and liable to be killed by any one if he remained at Rome ; but he did not cease to be a Roman citizen, unless he became a member of another state, and, if the ban was removed, he might return and resume the exercise of his rights. But under the Empire two special forms of banishment were introduced,—Ellegzitio, when the offender was sent to some place more or less distant, and obliged there to remain, but he still retained his personal liberty and the Roman civitas, e.g., Ovid at Tomi ; and Deiortatio, when the offender was conveyed to one of the rocky islets off Italy or in the tEgean, which were in reality state prisons : Exsiliusn was applied to both these forms (as well as to the earlier republican banishment), but was especially used for the more ignominious de,6ortatio.