Many tunicates are much smaller. This opening is about 1 1/2 wide and the whole tunicate was about 5 inches in length. I like the design within this "mouth" where food plankton in the water enter the tunicate and pass by ciliate cells to the esophagus. See Blue Tunicates and Red Sponge for a smaller type of Tunicate. They have a central nervous system so are classified as a chordata.
This image is available up to 7 x 10.