A parmularius was any of the various types of Roman gladiator who used a small shield called a parma. Due to having a large small shield parmularii would wear shin armour (ocreae) on both shins. This armour would be larger than the single ocrea worn on the right shin by a scutarius who carried a larger shield. Scutarii and parmularii are mentioned by Marcus Aurelius in his Meditations as two factions at the gladiator fights.
References
Parmularius (gladiator type) Wikipedia(Text) CC BY-SA