The Echinoid Directory

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Key to the genera of Spatangidae

1a. Irregular peripetalous fasciole, double in places, surrounds the petals Plethotaenia	1b. No aboral fasciole around petals Go to 2
2a. Aboral surface with enlarged tubercles only adjacent to the anterior ambulacrum and along the posterior interambulacrum Granopatagus	2b. Aboral surface with primary tubercles scattered in all interambulacral zones Spatangus