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