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periostracum

American  
[per-ee-os-truh-kuhm] / ˌpɛr iˈɒs trə kəm /

noun

plural

periostraca

  1. the external, chitinlike covering of the shell of certain mollusks that protects the limy portion from acids.

Other Word Forms

  • periostracal adjective

Etymology

Origin of periostracum

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

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.