Mermaid’s Purse - Catshark Egg Case
Many species of catshark (family: Scyliorhinidae) lay eggs in tough egg cases known as mermaid’s purses. These cases have curly tendrils that tangle around objects to prevent them from floating away.
The gestation period of the egg can range from a few months to over a year, depending on the species and water temperature. If held against a light source, the developing embryo can easily be seem.
Sander van der Wel via Flickr