Bivalves such as these shells are the prey of carnivorous snails. These snails have a tooth-studded tongue called a radula, which the snail uses as a drill to gain access to the tender parts inside. The radula is used to scrape and scrape, leaving a round hole. If you’ve ever picked up shells on the beach featuring neat round holes, you can figure out how that clam died-—clamicide. While reading this article, the first thing I thought was that someone collected shells with pre-drilled holes to string them from, courtesy of a predatory snail.
Wow, that is some strange stuff.