The Echinoid Directory

Key to the genera of Pygorhytidae

1a. Periproct aboral and in well developed anal sulcus.

1b. No extensive anal sulcus on aboral surface; periproct marginal.

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2a. Ambulacra forming shallow furrows as they approach the depressed peristome. Periproct with distinct subanal furrow.

2b. Ambulacra and peristome flush on oral surface. Periproct also more or less flush.