11.   The ventral interradial area is covered by similar spinelets to the dorsal side.

12.   The ventral interradial areas are also covered by low granules.

13.   The ventral interradial areas are also covered by naked skin.

14.   The ventral interradial areas are also covered with spinelets although the extent and density of covering varies.

15.   The ventral interradial areas are also covered with spinelets which are more nearly granular than those of the dorsal side.

16.   The ventral interradial areas are covered by plates and granules like those of the dorsal side.

17.   The ventral interradial areas are covered by plates similar to those on the dorsal surface.

18.   The ventral interradial areas are covered by scales like those of the dorsal surface but the rod-like spinelets are usually smaller.

19.   The ventral interradial areas are covered with large plates sometimes bearing a spinelet.

20.   The ventral interradial areas are covered with small plates armed with simple rods like those of the dorsal surface.