This urchin, commonly known as the slate pencil urchin, red slate pencil urchin, or red pencil urchin, is found throughout the tropical waters of the Indo-Pacific region, but is most abundant in Hawai‘i. Specimens from Hawai‘i tend to have bright red spines, while specimens from other parts of the Pacific may have yellowish or brown spines.

Heterocentrotus trigonarius

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 mammillatus is a similar, related species.-References:* *...

is a similar species that has longer and darker spines.