- Phylum Mollusca is the second largest animal phylum.
- They are bilaterally symmetrical, triploblastic and coelomate animal.
- Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump.
- A soft and spongy layer of skin forms a mantle over the visceral hump, the space between the hump and the mantle is called the mantle cavity in which feather like gills are present.
- The anterior head region has sensory tentacles and the mouth contains a file-like rasping organ for feeding, called
- They are usually dioecious and oviparous with indirect development.
Examples- Pila (Apple snail), Pinctada (Pearl oyster).