Red slate pencil urchin

''Heterocentrotus mamillatus'', 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'' is a similar species that has longer and darker spines.