Telepathic species
A telepathic species was one that naturally had partial or full telepathic or mental abilities. Telepathic species were able to sense things that non-telepathic species could not, including other telepathic activity. () It was often considered impolite to not speak aloud when among non-telepaths. (; )

Gem's empathic abilities seemed to indicated to Spock that it was an unlikely possibility that she was telepathic. Spock further stated that "over ninety eight percent of the known telepathic species send thoughts as well as receive them." ()

The Cairn were a telepathic species that had no concept of spoken language. ()

The Devore were extremely fearful of telepathic species. According to Inspector Kashyk, Trust was "a concept alien to the telepathic races. Why take someone at their word when you can simply read their mind?" ()

Telepathic species 

de:Liste von telepathischen Spezies
nl:Telepathische rassen
Lifeform classifications