The Echinoid Directory

Key to genera of Pourtalesiidae

1a. Periproct aboral and with subanal rostrum with ring-like subanal fasciole.
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1b. No subanal rostrum. Periproct marginal or inframarginal.

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2a. Anterior of test (towards top) extended out making the test vase-like.


2b. Anterior of test (towards left) not extended.

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3a. Anterior (to right) broadened and bilobed so that test outline is triangular.


3b. Test cylindrical at anterior (to left).

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4a. Plating in posterior ambulacra continuous.


4b. Posterior ambulacral plating disjunct; separated by plates of interambulacra 1 and 4 meeting along the midline.