So asked Foursquare founder, Dennis Crowley, this weekend. The Hampton-going tech geek apparently spotted "Thousands" of these things on the beach.  Curious too? Find out what's all over the beaches out east below...

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(via Wiki) Mermaid's purses (also known as Devil's Purses) are the egg cases of skates, sharks and rays. They are among the common objects which are washed up by the sea. Because they are lightweight, they are often found at the furthest point of the high tide. The eggcases that wash up on beaches are usually empty, the young fish having already hatched out.

The size of mermaid's purses vary; those of the small-spotted catshark or lesser spotted dogfish, Scyliorhinus canicula, are around 5 centimetres (2.0 in) long, while those of the greater spotted dogfish, S. stellaris, are around 10 centimetres (3.9 in). That excludes the four long tendrils found in each corner, which assist in anchorage. Mermaid's purses from rays vary in that they have points rather than tendrils. The colour and shape of mermaid's purses also varies greatly from species to species.

The young fish would normally gestate between 6 to 12 months, but can be much longer for deep sea catsharks which lay their eggs in very cold water.

If a mermaid's purse is still moist (not dried out) and has no visible hole, it is probably still occupied.