plural periostraca
: a chitinous layer covering the exterior of the shell in many mollusks, being usually well developed in freshwater forms, and serving to protect the shell from corrosion

Word History


New Latin, from peri- + Greek ostrakon shell

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Dictionary Entries Near periostracum

Cite this Entry

“Periostracum.” Dictionary, Merriam-Webster, Accessed 22 May. 2024.

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