The Echinoid Directory

1a. Apical disc with three gonopores.

1b. Apical disc with four gonopores.

2a. Apetaloid.

2b. Petals developed.

3a. Anterior convex without the slightest sign of a sulcus.

3b. Anterior ambulacrum forming weak to modest sulcus at ambitus.

4a. Petals closing distally. Labral plate extending to fourth ambulacral plate.

4b. Petals parallel and open-ended. Labral plate extending to second or third ambulacral plate.

5a.Tubercles not noticeably enlarged inside the peripetalous fasciole and not arranged in lines.

5b. Bands of coarse, aligned tubercles inside the peripetalous fasciole.

6a. Petals flush. Peristome small and ovate.

6b. Petals weakly depressed. Peristome D-shaped and relatively large.

7a. Large bilobed subanal fasciole. Peristome anterior and labral plate projecting.

7b. Subanal fasciole ovate. Peristome small, without protruding labral plate.