Lit·to·ri·na n.  Zool. A genus of small pectinibranch mollusks, having thick spiral shells, abundant between tides on nearly all rocky seacoasts. They feed on seaweeds. The common periwinkle is a well-known example. See Periwinkle.
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  Littorina
       n : type genus of the family Littorinidae: periwinkles [syn: genus
           Littorina]