The Gallamites were a spacefaring humanoid species. They had "toothy smiles," and transparent skulls through which brains twice the size of a Human's were visible. (DS9: "The Maquis, Part I")
In 2375, during the Dominion War, the Gallamites contributed duranium to the Federation Alliance. (DS9: "Penumbra")
This species was only mentioned in dialogue.
The Gallamites were mentioned in the pronunciation guide of the script of "Paradise", but not in the script itself. It is possible that the references were removed in an early draft.
According to StarTrek.com, the apparent home star and/or homeworld of the Gallamites was called Gallam.
A Gallamite man called Dabisch is the communications officer on Pike's Enterprise in Where Sea Meets Sky and other works.