Ambulacral region

It's the region that separates the pentaradially organized growth sections of the test. We can find the tube feet in this area and pedicellaria.

There are the pore-pairs that connect the tube-feet with the vascular system.

The upper edge of the ambulacral region is on the aboral side and the lower on the oral side.

These species have simple ambulacral plating, which means that the tubercles don't overlap with the adjacent plates.