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The Echinoid Directory

Key to the genera of Cidarinae
1a. Genital plates in females with deep brood pits.
Almucidaris

1b. Genital plates unmodified.

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2a. Spines with long collar, tuberculate on one side; distal part of spine with fine longitudinal striae.

Acanthocidaris

2b. Spines with short collar; either smooth or ornamented.

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3a. Primary spines with three or four prominent whorls.

Plococidaris

3b. Primary spine without whorls.

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4a. Primary spines with flange-like spines and ribs. Secondary spines small and scale-like.
Chondrocidaris

4b. Primary spines without flanges.

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5a. Primary spines with smooth, glabrous shaft, with only faint ribs distally.
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5b. Primary spines with ribbed or beaded shaft.

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6a. Ambulacra 40-50% width of interambulacra; genital plates radially elongate and widely in contact.
Centrocidaris

6b. Ambulacra about 30-35% width of interambulacra; genital plates only just in contact - not radially elongate.

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7a. Primary spines completely devoid of cortical hairs
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 7b. Shaft of primary spines with cortical spines that coalesce to form a smooth outer layer.
8a. Granulation moderately well developed outside the scrobicular circle on interambulacral plates.

 8b. Sparse granulation outside scrobicular circles on interambulacral plates.