- This boss is from Sonic Rivals. You may be looking for Egg Turtle (Sonic Rush).
The battle takes place upon a circular field. Players will run around the field as the head of the turtle chases them. At random instances, it will pop out both its head and its tail. Jumping on the head gains the player a hit, while jumping on the tails sends out a shockwave that will damage the other player. After a certain amount of hits, the Egg Turtle will spin faster.
The first player to accumulate six hits wins the battle, and the boss is destroyed.