Home > Invertebrates > Sea Urchins > Heterocentrotus mamillatus

Updated 8/7/2025

Family Echinometridae

INDO-PACIFIC / HAWAII

Heterocentrotus mamillatus

Slate Pencil Urchin, Blowhole, 10 feet, 50mm

Blowhole, Oahu, Hawaii, 20 feet

Sea Cave, Oahu, 45 feet

 

Palea Point, Oahu, Hawaii, 25 feet

 

Lanai Lookout, Oahu, 35 feet

Kailua Bay, Hawaii, 20 feet

 

Kapoho tidepool, Hawaii

 

Ahihi Bay, Maui, 4 feet

 

Honokohau, Hawaii, 10 feet

 

Molokini Back Wall, 30 feet

 

Makapu'u, Oahu, 20 feet

 

Juvenile, Makapu'u, Oahu, 15 feet

Sea Cave, Oahu, 45 feet

 

Night, Lana'i Lookout, Oahu, 15 feet


Hanauma Bay, Oahu, 25 feet


Kahe Point, Oahu, 10 feet


Blowhole, Oahu, Hawaii, 20 feet
   

SLATE PENCIL URCHIN

Locally abundant in clear shallow water.  Rare outside the Hawaiian Islands.  Spine shape variable.  Pale brown with light bands at night.  Overall diameter of 10 inches.  Red Sea to Okinawa, Hawaii, and Pitcairn.