Mollusca
Animals and organisms in the phylum, Mollusca, are also known molluscs. This phylum contains mostly marine organisms. This group of organisms has 85,000 different species, which make up 24% of organisms that are underwater. It is made up of organisms that mostly resemble slugs and snails, known as gastropods, which make up 80% of the phylum. Molluscs have 3 central features that allow them to be identified as mollusks. An important feature that all molluscs have is a nervous system, which allows them to feel and move. Another important feature is a cavity that allows the molluscs to feed and use their tongue. The last major feature that each animal has is the mantle, which a hole that allows the molluscs to breathe. The animals in this phylum do not have skeletal systems, or a system of bones within the body. The closest thing that some organisms have is a shell, which is slightly classified as an exoskeleton.
Snails are apart of the Mollusca phylum, but it doesn't have a definite skeletal structure. There is not a single bone within the body of a snail. They have some small features The only remnants of a skeleton is the snails shell. This shell serves as a type of exoskeleton and provides some structure to the snail's body. They are very small and don't walk, but the slide and slither to move.
An animal that is apart of the Molluscs phylum is the Blue-Ringed Octopus. It is a very poisonous octopus that inhabits the reefs between New Zealand and Australia. This animal, like the snail, does not have a definite skeletal structure. The Blue-Ringed Octopus has tentacles and a body that is completely made up of muscles, like most octopuses.
Another animal in this group is the clam. The inner part of the clam has no skeletal structure. It is mostly made up of muscles. The shell that houses doesn't serve as something that helps the the clam's structure, like other animals.