probably 1st husband of Scribonia.

3rd praetorian prefect of Syria under Pompey (59-57 BCE)
consul of Rome in 56 BCE.

References: Suetonius, Life of Augustus 62.
                   Appian, Syrian Wars 8.51.

Other resources on line:

• Gnaeus Cornelius Lentulus Marcellinus -  entry in the Wikipedia web.