These specimens are the egg cases of the Knobbed Whelk. The Knobbed Whelk is a species of large predatory sea snail. The egg cases of a Knobbed Whelk are commonly called a "Mermaid's Necklace." The egg cases are stringed together and the strings range in size from 5.5 cm - 12 cm long and 1.5 - 2 cm wide. The individual egg case ranges in size from approximately 1.5 - 2 cm long and 1 - 1.5 cm wide.