Green Sea Urchin test (also known as Sea Urchin Shell or Test)
Phylum: Echinodermata, Class: Echinoidea, Order: Echinoida, Family: Strongylocentrotidae, Genus: Strongylocentrotus, Species: S. droebachiensis · Strongylocentrotidae (Strongylocentrotid urchins) · Echinoid test (endoskeleton of a marine invertebrate, roughly spherical shape)
Species
Strongylocentrotus droebachiensis (Confidence level: High)
Shell Type
Echinoid test (endoskeleton of a marine invertebrate, roughly spherical shape)
Family
Strongylocentrotidae (Strongylocentrotid urchins)
Size
Approximately 2 to 2.5 inches in diameter, which is average for an adult specimen of this species. Adults typically range between 1.5 and 3 inches.
Color & Pattern
Muted earthy tones featuring a combination of olive green, grayish-brown, and subtle hints of mauve or purple radiating along the ambulacral and interambulacral plates. The colors are natural, showing minor fading consistent with a dried test.
Rarity
Common, frequently found washed ashore or collected in rocky northern coastal regions.
Habitat
Inhabits rocky subtidal and intertidal zones, often found in kelp forests, tide pools, and areas with hard substrates from the low-tide line down to depths of over 100 meters. Marine environment.
Geographic Range
Circumpolar distribution in cold northern waters, including the North Atlantic (down to Cape Cod in the US and the English Channel in Europe) and North Pacific oceans.
Description
A fragile, hemispherical endoskeleton or test of a sea urchin. It exhibits intricate radial symmetry with alternating rows of perforated ambulacral plates and tubercle-bearing interambulacral plates where movable spines were once attached. The apical disk is visible at the top, surrounded by genital and ocular plates.
Key Features
Spherical to slightly flattened shape, distinct rows of small tubercles for spine attachment, five-part radial symmetry, and an intact apical system at the summit.
Collector Value
Low to moderate commercial value. Popular in decorative crafts, shell shops, and educational displays. Typically sold for a few dollars depending on size and condition.
Condition Notes
Good condition. The test appears largely intact with minimal structural damage, though it lacks spines, pedicellariae, and tube feet, which is standard for dried tests. Graded as Fine condition for a beach-combed or dried test.
Interesting Facts
Living sea urchins move using hundreds of tiny, suction-cup-tipped tube feet and graze on algae using a complex five-jawed mouth apparatus known as Aristotle's lantern. Their tests are made of interlocking calcium carbonate plates.
Ecological Role
Key herbivorous grazers in kelp forest ecosystems, helping to control macroalgae populations. They serve as prey for sea otters, large fish, crabs, and gulls. Not currently endangered.
Similar Species
Purple Sea Urchin (Strongylocentrotus purpuratus) which tends to have a more uniform deep purple coloration; and the Red Sea Urchin (Mesocentrotus franciscanus) which grows significantly larger.
Beach Finding Tips
Look along rocky shores, tide pools, and beaches adjacent to kelp beds, especially after heavy storms or rough wave action that dislodges them from the subtidal zone.