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Pencil Sea Urchin

Heterocentrotus trigonarius, commonly known as the slate pencil urchin or red slate pencil urchin, is found in the tropical waters of the Indo-Pacific region including China, the Philippines, southern Japan, and South Pacific Islands. Pencil urchins get their name because of their unusually large spines that resemble pencils. This species can grow to a diameter of 3 inches (8 cm) in diameter, with spikes up to 4 inches (10cm) in length.