a man of Senatorial rank, connected by marriage with the family of Vespasian, and an intimate friend of Domitian, was appointed by Mucianus praefect of the praetorian guards in A. D. 70, a dignity which his father had formerly held under Caligula. (Tac. Ann. 4.68
.) Clemens probably did not hold this command long, and the appointment of Mucianus may have been regarded as altogether void, as Suetonius says (Tib.
6), that Titus was the first senator who was praefect of the praetorians, the office being up to that time filled by a knight. Notwithstanding, however, the friendship of Domitian with Clemens, he was one of the victims of the cruelty of this emperor when he ascended the throne. (Suet. Dom. 11