The Echinoid Directory

Key to the major groups of Cidaroidea (2)

12a. Pore-pairs wide and conjugate, the two pores linked by a groove.
Rhabdocidaridae

12b. Pore-pairs separated by a raised interporal partition which may be quite wide.

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13a. Pore-pairs offset alternately in each column.

Diplocidaridae

13b. Pore-pairs uniserial in each column.

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14a. Spines fusiform or clavate; mamelons massive with reduced perforation.

Psychocidaridae

14b. Spines long, thin and cylindrical; mamelons relatively small with well developed perforation.

Polycidaridae