In zoology, any marine snail of the family Littorinidae, found on the shores of Europe and eastern North America. Periwinkles have a conical spiral shell, and feed on algae.
Red stands for hardiness and valour. White signifies purity and innocence. Blue represents vigilance, perseverance, and justice. The latest star, representing Hawaii, was added in 1960. Effective date: 4 July 1960.