The Echinoid Directory

1a.Periproct large and longitudinal; ambital or supra-ambital in position.

1b. Periproct small and subcircular; inframarginal in position.

2a. Ambulacral pore-pairs arranged as a single, straight to slightly offset row towards the peristome.

2b. Ambulacral pore-pairs arranged as multiple rows towards the peristome.

3a.Ambulacral plating pyrinoid from apex to peristome.

3b.Ambulacral plating entirely simple above the ambitus but pyrinoid adorally.