| Title | Periwinkle |
| Caption | Periwinkle refers to any number of littoral marine snails. Often Edible |
| Source | NOAA Photo Library |
| URL | http://www.photolib.noaa.gov/htmls/figb0525.htm |
| Creator | NOAA |
| Origin | Internet |
The OED defines "Periwinkle" as: "Any of numerous herbivorous gastropod molluscs of the family Littorinidae, which have a spiral shell and are abundant in the intertidal zone of rocky coasts."