Kelly was a male Human Starfleet crewman who lived during the mid-23rd century. He served in the operations division aboard the USS Enterprise under Captain James T. Kirk, as one of the ship's security guards.
In 2267, Kelly served on a security team ordered by Lieutenant Commander Giotto to hunt for the Horta on Janus VI. He was scouting on his own when the mother Horta attacked him. By the time help arrived, he had been completely dissolved by acid. (TOS: "The Devil in the Dark")