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Echinocystoida

plural noun
Echi·​no·​cys·​toi·​da | \"+sə̇ˈstȯidə\

Definition of Echinocystoida 

: an order of Silurian fossil echinoids having small irregular spheroidal or flattened tests

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History and Etymology for Echinocystoida

New Latin, irregular from Echinocystites, fossil genus of Echinodermata (from echin- + -cystis + -ites -ite) + -oida

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