The Halanans were a telepathic humanoid species. Their telepathy was a form of psychoprojective telepathy.
Halanans had double-pointed ears and appeared almost identical to the later discovered Ramurans of the Delta Quadrant.
In Halanan culture, one chose a companion for life and would not leave them.
Sometime in the 24th century, the species moved to New Halana, a planet that was terraformed by Gideon Seyetik. (DS9: "Second Sight")
According to StarTrek.com, the Halanans were from the planet Halana. This planet was the namesake for New Halana.