∞ generated and posted on 2016.09.03 ∞
Bivalves, snails, squids, octopi, and a number of other animals that either possess shells or, as is true among the squids and octopi, possess either degenerate shells or no shells at all.
These are all members of the animal phylum, Mollusca. Mollusks include among them filter feeders, herbivores, and carnivores. The majority of their diversity is seen in marine environments, less in freshwater environments, and even less so in terrestrial environments where mollusks are represented by the snails and slugs (the latter which are either shell-less snails or snails that possess a substantially reduced shell).
Figure legend: Slug, a shell-less snail, as photographed August of 2011 in Olympia, Washington, at the Phage Meeting salmon bake!
Mollusks have true coeloms but lack segmentation. The cephalopods, including lobsters and squids, are among the most sophisticated and intelligent of invertebrate animals.