The Echinoid Directory

Key to genera of Echinoida (1)

The suprageneric grouping of the Echinoida is based almost exclusively on the structure of the globiferous pedicellariae. Here an artifical key is provided to the identification of genera based on test characters alone. Although not entirely secure, it should be possible to place most species correctly using this.

1a.Peristome margin with shallow, unpronounced buccal notches.

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1b.Peristome margin with sharp and deep buccal notches.

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2a.Test slightly to strongly oval in plan view; peristome always large (>40% test diameter).

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2b.Test circular; peristome generally small in adults (<35% test diameter) - but can be larger in small species.

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3a.3 pore-pairs to each compound plate.

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3b.4 or more pore-pairs to each compound plate.

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4a.Strictly 4 pore-pairs to each compound plate.

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4b.5-18 pore-pairs to each compound plate.

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