A reader wrote to us the other day about a unique worm that she found on the beach in Port Aransas, Texas. The worm (or rather, worms – she found several) are covered in what appear to be dozens of small shells. The reader attributed agency to the worm, suggesting that the worm had perhaps “decorated” itself with the shells, much like a decorator crab wraps itself in seaweed to blend in with its surroundings. Many of these strange worms, which were a few inches long on average, were found on the beach, although a few others were found in the water, where they were partially buried in sand. (Presumably, these worms were right by the shore, or else our reader must have been diving to the explore the ocean’s floor.) What are these worms?