The Gentons were a civilization that fought the Gentonian trade wars some time ago. They were one of the races visited by a group of Ullians in the mid-24th century for their memory archive project.
A Genton contingent met with Jev and Tarmin for the telepathic memory retrieval project. (TNG: "Violations")
This species was only mentioned in dialogue.
According to StarTrek.com, the Gentons hailed from the planet Genton (pronounced "JEN-tawn"). The trade wars were dated to a generation or two before the 2360s. [1](X)