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