It is uncommon to find whole Pacific Sand Dollar (Dendraster excentricus)
shells, called tests, washed up on the beach, so we were amazed to see many of them in one area. This is a true Sand Dollar, it does not have the 5 holes found in Key Hole Urchins. These echinoderms are related to sea urchins, sea cucumbers, and sea stars (a.k.a. "starfish"). The "doves" found in the inside of sand dollars are actually their "teeth"! Inside the living animal, they are arranged in the shape of a star in an organ called "Aristotle's Lantern". The live animals have a grayish-brown fuzz on the outside of the shell. The "flower" shape on the top of the test where the animals breathes. The little lines (channels) on the under side of the test funnel to a hole in the center, the mouth. Tiny feet move small pieces of food along these channels to the mouth. A second, smaller hole at the edge of the shell is the anus.
The living animals should never be collected and removed from the water, dead urchins stink! I've seen stacks of dead urchins left on picnic tables at eastern beaches because parents wouldn't let their kids take them. I don't buy shells from shell shops, most likely the animals were taken from the ocean alive and then killed, "perfect" seashells are seldom found on the beach.