When saltmarsh periwinkles (Littoraria irrorata) and saltmarsh coffeebean snails (Melampus bidentatus) are juveniles, their shells can be more colorful than those of adults. The upper image below is of a baby periwinkle (about 4 mm shell height), and the lower one is a coffeebean baby (about 3 mm shell height). Juvenile periwinkles smaller than about 5 mm hide inside furled leaf blades of smooth cordgrass, at least during the day. The more colorful shells of the hiding juveniles has caused at least one investigator to misidentify the juveniles as another species (Temkin, M.H. 1983. Elevational variations in sex ratio, growth rate and density of the marsh periwinkle, Littorina irrorata. MSc Thesis, American University, Washington, DC). No one knows how the periwinkles go from planktonic veliger larvae to settled minute juveniles inside furled leaves.