[ per-ee-os-truh-kuhm ]
/ ˌpɛr iˈɒs trə kəm /
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noun, plural per·i·os·tra·ca [per-ee-os-truh-kuh]. /ˌpɛr iˈɒs trə kə/.
the external, chitinlike covering of the shell of certain mollusks that protects the limy portion from acids.
Were you ready for a quiz on this topic? Well, here it is! See how well you can differentiate between the uses of "was" vs. "were" in this quiz.
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“Was” is used for the indicative past tense of “to be,” and “were” is only used for the subjunctive past tense.

Origin of periostracum

1830–40; <New Latin, equivalent to peri-peri- + ostracum a shell <Greek óstrakon.See oyster

OTHER WORDS FROM periostracum

per·i·os·tra·cal, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use periostracum in a sentence

  • 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