The common name for members of the genus Littorina and its relatives is periwinkle. This is a marine snail, living on hard surfaces in the littoral zone. Periwinkles serve as human food in various places. Note the eyes placed on protuberances next to the tentacles. Also note the snout, characteristic of many prosobranch groups.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature