Devil’s Purse

Colored pencil drawing of a clearness skate egg case by Mike Palmer (2023). Original hand-colored art and art prints available here.

The wrack line forms where high tide drops the floating ocean debris - both organic and man-made. Mixed in among the seaweed, eel grass, and bits of crustacean one can often find black leathery pouches known as a “devil’s purse”. These pouches have a distinctive flattened, rectangular shape with tendrils or horns at the corners, resembling purse strings or devil's horns, hence the name.

These odd pouches are actually egg cases produced by a type of fish called skate. Among the most common egg cases found along Cape Cod beaches are those of the clearnose and little skates. The pouch of each species differ slightly, and can be easily identified by size and shape. The tendrils on the case are useful for anchoring the case to the sea floor until the skate hatches.

Colored pencil drawing of a little skate by Mike Palmer (2023). Original hand-colored art and art prints available here.

These egg cases play a crucial role in the reproduction and life cycle of skates, with the cases forming a protective case for the developing embryo. The embryos incubate inside the case for about 3 months. Eventually, the embryo grows too big and it will break free when it reaches about 5 to 6 inches in length.

While the terms "devil's purse" may not have scientific significance, it provides a way for people to describe and engage with the natural world, linking folklore and natural history.