Each of the invertebrate groups has its own subpage(s), and a few representative pictures to help you figure out what that group looks like.

Group	Sample Photos
Abalones
Anemones A-L Anemones M-Z
Arthropods
Barnacles
Bivalves
Brittle Stars
Bryozoans
Chitons
Corals and Gorgonians (and other colonial cnidarians, including sea pens)
Crabs
Hermit Crabs
Hydroids
Jellyfish (and comb jellies)
Limpets
Nudibranchs A-L Nudibranchs M-R Nudibranchs S-Z
Octopuses and Squids
Salps
Sea Cucumbers
Sea Slugs (other than nudibranchs)
Sea Snails A-H Sea Snails I-Z (other than abalones)
Sea Stars
Shrimps and Lobsters
Sponges
Tube Worms
Tunicates (other than salps)
Worms (other than tube worms)