egg case

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A protective capsule that contains eggs, produced by certain insects, mollusks, and elasmobranch fishes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A protective capsule that contains the eggs of some insects and molluscs
• noun The leathery egg of certain marine animals such as sharks and skate