The Echinoid Directory

Key to genera of Pedinidae (1)


1a. Apical disc less than 25 % test diameter; genital plates not projecting strongly. Primary tubercles present on adapical plates.

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1b. Apical disc approximately half the test diameter; genital plates strongly projecting. Primary tubercles absent from aboral plates.


2a. Ambulacra with pore-pairs forming a single, slightly sinuous, vertical series.

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2b. Pore-pairs in strongly offset lines of three so as to form a wide adradial poriferous zone.

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3a. Ambulacra with primary tubercle only on every second or third compound plate

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3b. Primary ambulacral tubercle on every compound plate

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4a. Apical disc small in proportion to test diameter; aboral interambulacral primary tubercles displaced towards adradial suture. Ambulacra expanded into phyllodes adorally.


4b. Apical disc more than half test diameter; aboral interambulacral tubercles positioned subcentrally on plates. No phyllodes adorally.