Heterocentrotus trigonarius
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. Heterocentrotus mamillatus is a similar, related species. Heterocentrotus trigonarius can grow to in diameter (spine-to-spine). The spines are potentially harmful to humans if trodden on. References Heterocentrotus Fauna of the Indian Ocean Fauna of the Pacific Ocean Animals described in 1816 Taxa named by Jean-Baptiste Lamarck