This order of shelled, and slug-like opisthobranchs contains species that mostly live on marine algae and are usually criptically colored. Their name (sacoglossans) comes from the sac used to catch their discarded worn teeth.
One peculiar family in this order contains snails with bivalved shells. The species were placed with the Bivalvia until the living animal was finally found and discovered to be a gastropod.
- 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