1a.No lunules at any size. |
1b.Ambulacral notches or lunules present from a small size. |
2a. Anal lunule always present in posterior interambulacrum. |
2b. Anal lunule absent, ambulacral lunules or notches only. |
3a.Radial water canals and associated tube-feet extending far onto interambulacral areas; interambulacral zones at ambitus rarely less than 50% width of ambulacral zones. |
3b.Food grooves and pores for tube-feet confined to ambulacral areas; interambulacral zones tapering towards ambitus where they are usually less than 20% the width of ambulacral zones. |
4a.Lunules or notches festooned in construction; absent from posterior ambulacra. Interambulacral zones only ca. 20% width of ambulacral zones at ambitus. |
4b. Lunules or notches cross-linked in construction; always present in posterior ambulacra. Interambulacral zones almost as wide as ambulacral zones at ambitus. |