This image is of a muffin crab fossil aka Avitelmessus grapsoideus (Rathbun, 1923) on display at Mace Brown Museum of Natural History (August 2017). It was found in North Carolina USA and dates to the Cretaceous Period (80 million years ago).
The
Mace Brown Museum of Natural History is located at the College of
Charleston, 202 Calhoun Street, 2nd Floor, Charleston, South Carolina
29424.
Learn more at their blog: http://blogs.cofc.edu/macebrownmuseum/