Complex sentence: For a few days, Primus was virtually ruler of Rome, and the Senate bestowed upon him the rank and insignia of a consul, but on the arrival of Licinius Mucianus, he left Rome.
Split into simpler sentences: For a few days, Primus was virtually ruler of Rome, and the Senate bestowed upon him the rank and insignia of a consul. But on the arrival of Licinius Mucianus, he left Rome.