Michael Barrier played Lieutenant DeSalle in three episodes of The Original Series, first as a navigator and later as the assistant chief engineer left in command in Catspaw.
Michael Barrier appeared as Lieutenant Vincent DeSalle in The Squire of Gothos, This Side of Paradise and Catspaw.
In The Squire of Gothos DeSalle is the navigator who joins the landing party on Trelane's world and tries, unsuccessfully, to take the alien by surprise with a phaser. In This Side of Paradise he is among the crew who fall under the influence of the spores on Omicron Ceti III.
By Catspaw, in the second season, the character has moved to a red uniform and is described as assistant chief engineer. With Kirk, Spock, McCoy, Scott and Sulu all on Pyris VII he commands the Enterprise, working with Chekov to break the force field that Sylvia and Korob have thrown around the ship.