Sentence:  We may, therefore, assume two epochs for the Saturnian verse. In the first epoch, until Livius and Saevius, its measure is yet very unsettled; the rhythm is, however, evidently trochaic. It usually corresponds to two <WSD>ithyphallics</WSD>, sometimes with, sometimes without an anacrusis before the first <WSD>ithyphallic</WSD>. 
Meaning of the word marked with <WSD> tags:  A poem or song in an ithyphallic metre.