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1a. Apical disc includes complemental plates separating genital plates 1 and 4.
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1b. Apical disc compact
Go to 2 |
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2a.Periproct opening in direct contact with the apical disc.
Pygopyrina |
2b.Periproct opening separated from the apical disc by several interambulacral plates.
Go to 3 |
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3a.Ambulacra with simple plating throughout.
Galeritidae |
3b. Ambulacra with occluded plates (pyrinoid plating).
Go to 4 |
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4a.Periproct marginal to inframarginal. Pore-pairs becone crowded into offset triads towards the peristome.
Conulidae |
4b.Periproct oral. Pore-pairs uniserial to the peristome.
Echinoneidae |
