The Echinoid Directory

Salenioida: Key to major taxa

1a. Ambulacral plating trigeminate adorally, unigeminate aborally. Adapical interambulacral tubercles perforate.

Go to 2

1b.Ambulacral plating bigeminate or (rarely) unigeminate adorally. Interambulacral tubercles always imperforate.


2a. Apical disc without sutural pitting; periproct displaced towards genital plate 5.

Go to 3

2b. Apical disc with obvious sutural pitting - those pits having small tubercles. Periproct displaced towards ocular plate I.

Go to 4

3a. Ambulacra with every third tubercle enlarged; ambital and adoral ambulacral tubercles perforate and crenulate.


3b. Ambulacra narrow with simple plating except close to the peristome; ambulacral tubercles imperforate.


4a. Ambulacral plating trigeminate below the ambitus and bigeminate above. Ambital and adapical tubercles obviously perforate.

Go to 5

4b. Ambulacral plating polygeminate with well developed phyllodes adorally and trigeminate aborally. Adapical interambulacral tubercles with rudimentary perforations only.


5a. Primary tubercles on all adapical interambulacral plates.


5b. Adapical interambulacral plates lacking a primary tubercle.