Genus Littorina refers to a group of small marine snails known as periwinkles. These snails are commonly found along rocky shores, and several different species are recognized within this genus. Some of the synonyms for Genus Littorina include the common periwinkle, black snail, rough periwinkle, and the flat periwinkle. Each of these names may refer to a specific species within Genus Littorina, or to the group as a whole. These snails play an important role in the marine ecosystem, serving as a food source for many predators and helping to maintain the balance of coastal ecosystems.