The Echinoid Directory

Key to the genera of Echinocystitidae

1a. Ambulacral pore-pairs arranged as a single perradial column in each half ambulacrum.
Gotlandechinus

1b. Ambulacral pore-pairs forming a biserial adradial band in each half ambulacrum.

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2a. Interambulacral zones composed of plates that are somewhat variable in size and shape.
Echinocystites

2b. Interambulacral zones composed of plates that are usually hexagonal, and of similar size.

Rhenechinus