Strongylocentrotidae

Family: Strongylocentrotidae

Group: Marine Invertebrate, Species

Scientific Name	Common Name	Summary
Strongylocentrotus droebachiensis	Green sea-urchin	This is the common species of harbors, calm bays, and tidal flats. Compared to Strongylocentrotus purpuratus, this species is pretty "wimpy," with slender spines and a more fragile look and feel overall.The real identification problem comes from White sea urchin (Strongylocentrotus pallidus), which is a subtidal species which tends to be paler and not as tall proportionately as this species. If you have a test or a particularly perplexing specimen, look closely at the pores: in this species they are arranged in sets of five pairs, as opposed to six or seven pairs in White sea urchin (Strongylocentrotus pallidus).
Strongylocentrotus franciscanus	Red sea urchin	This sea urchin is commercially important, and a prize find for the intertidal beachcomber. It is much more common subtidally, and is sometimes so tightly wedged in its space that prying it off is near impossible without breaking the fragile test. It is distinguished from Strongylocentrus purpuratus by its long and red, rather than short and purple, spines. Some specimens have purple spines, but they are still quite a bit longer than those of the purple sea urchin. Some hybrids are reported.
Strongylocentrotus pallidus	White sea urchin	Less common than the green sea urchin, to which is is similar. Also found in shallow waters.