The Pencil urchin lives on the reef which surrounds the islands of Tahiti.

It is composed of long spines on the upper part of the urchin shell with spines of diminishing size towards the undersize, around its beak, becoming flatter as they become smaller.

The longer and pointed spines are its protective armour and the smaller and flatter spines are used for movement.

Colours vary from olive greens through several shades of purple.