National Park Service’s Post

“Thats’s my purse. I don’t know you!” - Bobby Hill Ever stumbled across a black, leathery, palm-sized pouch washed up on the beach? Often called a “mermaid’s purse,” these aren’t treasures from Ariel’s collection of "whozits and whatzits” but egg cases of certain sharks and skates—close cousins to rays with flattened bodies and broad pectoral fins. Each egg case has four “horns” in total, one on each corner, which help anchor the case to seaweed on the bottom of the sea floor. When the embryo has finished developing, the pouch opens and the young one emerges. Most of the time, the egg cases you find washed up on shore are empty. Image: Is there a black purse in here? Four leathery looking egg cases lying in the sand at Gateway National Recreation Area.