These animals have a globular or flattened skeleton called a test covered with hundreds of moveable spines, tube feet and tiny pincer-like organs called pedicellaria. The 2 basic groups are the Regulars, the sea urchins and the Irregulars, the heart urchins, sand dollars, etc. We will concern ourselves here with the Regulars. These have spherical tests, a fragile body shell, with either sharp, slender spines or massive blunt ones that radiate from the pores on the test's surface. Five sections, like hollow orange slices, from the underside mouth to the anus form this test. Their mouths are equipped with a complex 5-part radial set of jaws, called Aristotle's lantern, controlled by 60 separate muscles. These jaws can be used to scrape algae, attack and eat other prey, or drill into solid rock.

Pencil Urchin
(Heterocentrotus mamillatus)

It has solid, bright red, cube-like spines and short stubby spines that may be white to very dark red. The long red spines turn chalky white at night and used to be used in place of chalk when blackboards were made of slate.

To continue to the Sea Stars