The alder's necklace shell is a predator snail, which digs itself into the sea floor. Once washed ashore, it looks a lot like the common necklace shell, only much smaller. Live specimen hardly ever wash ashore. Sometimes, the empty shells wash ashore by the thousands, often between Den Helder and the Hook of Holland. Alder's necklace shells used to be a very rare find. Thanks to sand nourishments nowadays, you seem them much more often on the beach.