Both intertidal area and subtidal areas
On the beach
Intertidal area only
Subtidal area only
Porcupine
Dome
Toothpick
Pentamerous
Small fish
Sea cucumbers
Algae
Other sea urchins
Strongylocentrotus
Animalia
Echinoderms
Purpuratus
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
Because sea urchins have large numbers of eggs
Feet
Spine
Mouth
Nose