What is a "periwinkle"?

A periwinkle is a small, marine gastropod mollusk with a spiral-shaped shell. They are commonly found in intertidal zones, clinging to rocks or other hard surfaces. Periwinkles have cone-shaped shells with small openings at one end. They are known for their ability to withstand exposure to air during low tides by tightly sealing their shells to retain moisture. Periwinkles feed on algae and other organic matter, scraping it off surfaces with their radula, a specialized feeding structure. They play an important role in coastal ecosystems by contributing to nutrient cycling and serving as a food source for other organisms. In some cultures, periwinkles are consumed as a seafood delicacy, often boiled or steamed and served with butter or other seasonings.