Sea Urchins belong to Class Echinoidea (Phylum Echinodermata).
This is easily the most common sea urchin found on Axial. It is often observed hiding among the lobed basalt lavas. Its size is only 10-15 cm in diameter.
This urchin has only been observed on a few occassions and is not common at Axial. This specimen was seen at the base of Axial Seamount.