The Dachlyds were a space-faring civilization and neighbors of the Gemarians. They were described as "incredibly stubborn" by Counselor Troi.
In 2366, over a period of two weeks, Jean-Luc Picard successfully mediated a trade dispute between them and the Gemarians. The resulting agreement benefited both groups. (TNG: "Captain's Holiday")
This species was only mentioned in dialogue.