What kind of seafood has a hard outer casing but does not have bones or skeletal system?

The seafood you're thinking of is likely crustaceans.

Here's why:

* Hard outer casing: Crustaceans have a hard exoskeleton made of chitin, which provides protection and support.

* No bones or skeletal system: Instead of an internal skeleton, they have this external shell.

Examples of crustaceans include:

* Crabs

* Lobsters

* Shrimp

* Crayfish

* Barnacles

Let me know if you have other questions!