The animals listed below do not have a backbone or vertebra:
Snails, muscles, and abalone have a thick exoskeleton on the outside of their bodies.
Shrimp, crab, crayfish, and lobsters are also known as water insects. These arthropods swim in water instead of flying in the air.
Sharks and lampreys are not considered to be true fish as they lack a backbone. Their spine is made of cartilage instead of bone.
Note that these lowly animals used to be considered the poor man's food. Because most of these animal dishes are usually smothered with butter, and are now very expensive, some priests and bishops are suggesting or even mandating that people not eat these foods during Great Lent or during times of fasting.