This planet was only mentioned in dialogue.
- According to The Worlds of the Federation, Medusa is the fourth planet in the Xi Hydrae system. It is called Visalayan by its natives.
- The Star Fleet Medical Reference Manual described it as the fifth planet in the Xi Hydrae system.
- FASA's The Federation sourcebook described it as the fifth planet in the Rhys system.
- Star Trek: The Original Series - Core Game Book referred to the planet as Medusa III.
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