Two men collect shells at the beach on Topsail Island, North Carolina, on Sept. 12, 2018. Getty Images/LOGAN CYRUS

North Carolina beachgoers were baffled to see odd-looking objects resembling black pouches washing up on the shores this week. While people thought it to be black, plastic-looking “pouches,” they were not quite what they seemed to be.

Officials with the Cape Hatteras National Seashore clarified these objects were what was known as “mermaid’s purses” or “devil’s pocketbooks” — the egg casings of sea skates.

“No these are not pieces of plastic; they are skate eggs!” the Cape Hatteras National Seashore clarified on Facebook. “Skates are in the shark family but share a flat-like appearance similar to stingrays. These leathery pouches serve as an egg sack and are typically attached to a plant or other stationary object in the water,” the national seashore explained, adding the sacs typically “wash ashore after the skate has hatched.”

Some species of sharks, skates and chimaeras all produce strange leathery, alien-looking egg casings.

According to the New Jersey Division of Fish & Wildlife, a variety of skate species — such as the little skate, the barndoor skate and the winter skate — can be found off the coast of North Carolina.

The winter skate, specifically, reproduces late in life, usually when the creature reaches 11 years in age and roughly 2.5 feet in length, according to National Oceanic and Administration (NOAA). The winter skate “lay eggs year-round but have few offspring.” The eggs of skates incubate inside the hard case for roughly 6 to 12 months, according to NOAA.

​Skates resemble stingrays in appearance but they have contrasting methods of reproduction, according to the Florida Museum.

“Rays are live-bearing (viviparous) while skates are egg-laying (oviparous), releasing their eggs in hard rectangular cases sometimes called ‘mermaid’s purses,’” the museum stated, adding rays have spines on their tails while skates do not. Both rays and skates are “closely related to sharks.”

New Jersey Division of Fish & Wildlife stated: "An interesting fact about these fish is that stingrays have live births while skates lay eggs. You have probably seen the black egg sacks wash up on the beaches. They are commonly known as mermaid purses."