Shells are a form of virtual currency within Hatchlings. You can use them to buy particularly difficult eggs to finish a collection, open new collections with Turtle Keys, or lock bunnies in the Bunny Cage for an extended period of time. You can also use your shells to buy a Premium Membership.
How do I know how many shells I have?
At the top of the game, look for the picture of shells with a number next to it. That number is how many shells you have.
How do I get more shells?
You can earn shells in game by completing challenges, as a reward for leveling up, or sometimes as a prize for an event. If you need more shells, you have the option to purchase more in the Marketplace. There are also gift cards for shells that you can redeem if you are lucky enough to receive one for a friend!