 Complete the following phrase:  The numbering of the legions is confusing, due to duplicated and inconsistent numeration by various emperors. Several legions shared the same serial number with others. Augustus numbered the legions he founded himself from I, but at the same retained the serial numbers of those legions he inherited from his predecessors. This policy was generally followed by those of his successors who also founded new legions there were thus many legions numbered I. However, even this practice was not consistently followed. For example, Vespasian formed two new legions out of units disbanded in disgrace after the Civil War of 689, but gave them the same serial numbers but different titles as the disbanded ones. Trajan numbered the first legion he founded XXX because there were 29 other legions in existence at that time; but the second Trajanic legion was given the serial number II. XVII, XVIII and XIX, the numbers of the legions annihilated in the 