Sonic X-treme

Sonic X-treme was a platform game developed by Sega Technical Institute. It was being developed from 1994 until Sega cancelled it in 1997. It was meant to be the first 3D "Sonic the Hedgehog" game. It was also meant to be the first new "Sonic" game for the Sega Saturn. 
Background.
When Nintendo released Super Mario 64, it was a popular 3D platformer, so Sega wanted to compete with Nintendo with their own 3D Sonic game.
Development.
Sonic X-treme was developed for the Sega 32x, but then development moved to the Sega Saturn.
Story.
The story of the game was that Robotnik was trying to steal six magic rings from Tiara Boobowski and her father, so Sonic wants to stop him.
Cancelation.
Sonic X-treme was canceled in 1997 because of development issues and crunch time. To make up for this, SEGA put Sonic 3D Blast on the SEGA Saturn instead.