Complex sentence: Year 343 BC was a year of the pre-Julian Roman calendar.In the Roman Empire it was known as the Year of the Consulship of Corvus and Arvina (or, less frequently, year 411 "Ab urbe condita").
Split into simpler sentences: Year 343 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Corvus and Arvina (or, less frequently, year 411 "Ab urbe condita").