The Echinoid Directory

Key to Genera of Echinocyamidae

1a.Two radial struts internally (bordering periproct); periproct larger than peristome.

Mortonia

1b.Ten radial struts internally; periproct smaller than peristome.

Go to 2

2a.Tuberculation on oral surface without strong bilateral symmetry.

Echinocyamus - Go to 3

2b.Tuberculation on oral surface arranged with strong bilateral symmetry.

Leniechinus
3a. Conspicuous sunken oral region present
Echinocyamus (Lepidocyamus)
3b. No conspicuous sunken oral area
Echinocyamus s.s.