What are lower invertebrates?

Shrimp are one example of bottom feeding invertebrates. If you simply mean invertebrates that live on the sea floor, crabs, lobsters, and giant Pacific octopus would be examples. More examples would include sea slugs, sea snails, sea cucumbers (another bottom feeder), and bivalves (seashells like clams and oysters that have two shells that are attached to each other and can open and close like a hinge).