A six-person Starfleet science vessel that disappeared while surveying Lactra VII, whose surviving crew were found by the Enterprise living as exhibits in an alien zoo.
The USS Ariel is a small Starfleet science ship with a crew of six, commanded by Lieutenant Commander Tom Markel. It appears in the animated episode The Eye of the Beholder.
The Ariel goes silent after reaching the unexplored planet Lactra VII, and the Enterprise finds it empty in orbit. Its log shows that the crew beamed down in groups, each going to look for the one before.
Kirk, Spock and McCoy follow and are captured by the Lactrans, huge slug-like beings of enormous intelligence, who put them in a zoo. There they find Markel and the other survivors of the Ariel. Spock, helped by a Lactran child, persuades the keepers that humans are intelligent, and all are released.