How to Use My Fossil in "Pokemon Yellow"by Cynthia Chen ; Updated September 22, 2017
The Dome Fossil and Helix Fossil are key items introduced in Pokemon Red, Blue, and Yellow. In "Pokemon Yellow," the player obtains his choice of one or the other upon defeating the Super Nerd in Mt. Moon and subsequently defeating Jessie and James. The Dome Fossil yields Kabuto, while the Helix Fossil yields Omanyte. The player is able to revive his or her fossil of choice at the Pokemon Laboratory on Cinnabar Island.
Surf or Fly to Cinnabar Island and enter the Pokemon Laboratory to the left of the Pokemon Center. Go right and enter the third room.
Ignore the scientist offering to trade you a Muk for a Kangaskhan. Speak to the other scientist and give him the fossil of your choice from Mt. Moon. Exit the laboratory.
Deposit a Pokemon in a box if necessary to ensure you have a vacancy in your party. Return to the Pokemon Laboratory and speak with the scientist to whom you handed the fossil to obtain either Kabuto or Omanyte.