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keyhole urchin

noun
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Definition of keyhole urchin

: a flat sea urchin of the order Exocycloida with long narrow apertures occurring near the margin of the test

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“Keyhole urchin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keyhole%20urchin. Accessed 22 Jan. 2021.

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