Lacuna vincta, commonly known as the northern lacuna, the wide lacuna, the northern chink shell, or the banded chink shell, is a species of sea snail, a marine gastropod mollusk in the family Littorinidae, the winkles or periwinkles. It is found intertidally and in shallow waters in both the northern Atlantic Ocean and the northern Pacific Ocean. It is a herbivore, feeding on seaweed and diatoms with its toothed radula. Description The shell of Lacuna vincta is conical, with five to six smooth whorls and a pointed apex. The aperture is about half the height of the shell or slightly larger. The umbilicus has a prominent groove between two white ridges of columella. The exterior of the shell is pale brown with a broad spiral of white and a glossy periostracum. The interior of the shell is not white and pearly and the aperture can be closed by an operculum. The maximum recorded shell length is . Distribution and habitat The distribution of L. vincta is circumboreal, extending as far south in the Atlantic Ocean as the British Isles and France, and the eastern coast of North America. In the northeastern Pacific its range extends from Alaska to California, but it is seldom found further south than Washington state. It is present on algae on rocky shores, intertidally and down to about . In the British Isles, the larvae settle preferentially on brown seaweed such as Fucus serratus and Laminaria spp. and on short red seaweed such as Lomentaria articulata, as well as on the seagrass Zostera spp. In the Pacific they settle mainly on kelp, eelgrass and surfgrass. Ecology L. vincta is a herbivore, grazing on seaweed and on diatoms living on the surface of seagrasses. The radula has 45 to 95 rows of tiny teeth, with about three new rows being formed each day. Two separate types of teeth are produced; if the snail is grazing on seaweed, these newly formed teeth are sharply pointed and are used to tear deeply into the algal frond; if on the other hand, the snail is currently feeding on diatoms growing on seagrass, the new teeth are much blunter and are used to scrape diatoms off the leaves. The new teeth are formed at the back of the radula and work their way forward as the older teeth wear away and are discarded, so it takes some time for the snail's