Mouth
Feet
Nose
Spine
Porcupine
Pentamerous
Toothpick
Dome
Because sea urchins have large numbers of eggs
Because the eggs make great omlettes
Because a sea urchin's egg is relatively big
Because sea urchins have large numbers of relatively big eggs
Sea cucumbers
Other sea urchins
Small fish
Algae
Subtidal area only
Both intertidal area and subtidal areas
On the beach
Intertidal area only
Animalia
Purpuratus
Strongylocentrotus
Echinoderms