They are close to the top of the list when it comes to unusual objects that could be washed up on the beach.
The objects are sometimes referred to as "mermaid purses".
Sometimes they are also called "devil wallets".
But they are not a bag, purse or even man-made.
Instead, they are sharks.
The bags are often confusing to those who find them.
If you look closely, you can sometimes see a tiny shark puppy.
– Danielle Campbell (@ dani_b77) June 16, 2015
– cathleen clark (@ladyoflarkspur)  Purses "are made of collagen protein and feel soft and a little leathery.
Usually they have exits where the shark puppies have swum out. If not, the cubs did not survive.
Some have different shapes, including spirals.
Among the nine shark orders, oviposition can only be found in three shark varieties.
"About 43 percent of sharks and rays – including skates, most cat sharks, and the nine types of horn sharks – lay eggs rather than live young. California Horned Sharks are about every 10 to 14 days in spring and summer (the statistics are mainly based on aquarium research) and each contains a small embryo, "Science Daily writes in a report.
"It's unclear how this shape actually develops," said Christopher Lowe, a professor of marine biology responsible for the Shark Lab at Long Beach's California State University.
The report found that The "wrapping" of the egg from a material is similar to fingernails or hair.