INTERNAL ANATOMY

From The Fishery Biology of Sea Urchins in the Family Strongylocentrotidae, Washington Department of Fisheries, 1976

If you cut the sea urchin along the equator you will see the following:

Am and Im are the ambulacral and interambulacral areas respectively.

A is the "top" and B is the bottom or mouth side.

Gonads are usually yellow to orange in color [about the same color as the eggs]

Stomach and Intestines are usually olive drab to brown in color.