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[per-ee-os-truh-kuh m] /ˌpɛr iˈɒs trə kəm/
noun, plural periostraca
[per-ee-os-truh-kuh] /ˌpɛr iˈɒs trə kə/ (Show IPA)
the external, chitinlike covering of the shell of certain mollusks that protects the limy portion from acids.
Origin of periostracum
1830-40; < New Latin, equivalent to peri- peri- + ostracum a shell < Greek óstrakon. See oyster
Related forms
periostracal, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2016.
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Examples from the Web for periostracum
Historical Examples
  • Gray calls it the periostracum, from the membranous skin covering the bones of quadrupeds.

    A Conchological Manual George Brettingham Sowerby
  • The periostracum, or epidermis, is heavy and often velvety or even hairy.

    The Sea-beach at Ebb-tide Augusta Foote Arnold

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