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1b. Apetaloid aborally or with weakly differentiated pore pairs. |
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2a. Apical disc with four gonopores. |
2b. Apical disc with 3 gonopores (no opening in genital plate 2). |
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3b. Pore-pairs in frontal groove small with an interporal node and differentiated from those in other ambulacra. |
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4b. Peristome opening faces downwards; opening clearly visible in oral view. |
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5a.Petals short and narrow. |
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6a.Periproct opens below mid-height on short posterior face. |
6b.Periproct opens above mid-height. |