Echinodermata
Enchinodermata are a phylum of marine animals. The animals in this phylum are marine animals usually with five points such as a starfish and sand dollars. There are no fresh water animals in this phylum only salt water. This phylum contains about 70,000 different species.
Starfish
Starfish do not exactly have a circulatory system they have what is called a hemal system. The hemal system channels form rings around the mouth closer to the top of the starfish. Circulation occurs in three places: the perivisceral coelom, the water vascular, and the hemal system.
Sand Dollar/Sea Urchin
Sand Dollars and Sea uchin do not have circulatory systems, they have a network of water filler canals called the water vascular system to help them move and feed. They also have three largely independent fluid systems. The large filled coelom that surrounds the internal organs constitutes the major medium for internal transport. Circulatory currents set up by the ciliated cells of the coelomic lining distribute nutrients from the stomach to the body wall.