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