The Echinoid Directory

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Key to the genera of Pygorhytidae

1a. Periproct aboral and in well developed anal sulcus. Spatoclypus	1b. No extensive anal sulcus on aboral surface; periproct marginal. Go to 2
2a. Ambulacra forming shallow furrows as they approach the depressed peristome. Periproct with distinct subanal furrow. Pygorhytis	2b. Ambulacra and peristome flush on oral surface. Periproct also more or less flush. Pygomalus