The sand-bat was a species of animal indigenous to Manark IV that had the curious evolutionary property of appearing as inanimate rock crystals, until they attacked their prey.
In 2268, after Leonard McCoy noted that Gem seemed harmless, Spock cited these creatures as an example of a similarly safe-looking lifeform. (TOS: "The Empath")
External link[]
- Sand bat at Memory Beta, the wiki for licensed Star Trek works