|
1b. Ambulacral pores minute and single throughout. |
|
2b. Ambulacral plating uniserial adapically. |
3a. Ambulacra becoming uniserial adapically. |
3b. Ambulacra remain biserial to apex. Go to 4 |
4a. Labral plate relatively short and bearing spines; apical disc with only two large gonopores (sometimes with two smaller anterior gonopores). |
4b. Labral plate relatively long and without spines; apical disc with four large gonopores . |