Sea urchins (Echinoidea) is an animal that usually lives in one. coastal regions 2. the rocks 3. seabed 4. in mud 5. coastal wells wells-6. estuary of the river (to immerse yourself in clay or rock below)
The animals belonging to this class sleeveless round, but have the thorns that can be driven.
Examples of Echonoidea
Diadema antillarum
Strongylocentrotus (ball shaped)
Spatangus (oval)
Echinarachnius (shaped like a coin) which is often called sand dollars.
