The Echinoid Directory

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Key to the Pedinoida 1a. Ambulacral plating simple throughout. Go to 2 1b. Ambulacral plating compound in triads. Pedinidae 2a. Primary tubercle small and with broad granular zones; mamelon small. Orthocidaris 2b. Primary tubercle dominating interambulacral plate; with massive mamelon. Zardinechinus