periostracum

[per-ee-os-truh-kuhm]

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

Word History and Origins

Origin of periostracum¹

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

Example Sentences

For example, the researchers write that "the name highlights the ‘hardcore’ nature of Alviniconcha snails," and that "the spiky periostracum resembles the fashion of punk rock bands."

From The Verge

In some shells the periostracum is very thick and coarse, and must be removed before the shell itself can be seen; but it is always well to keep at least one specimen in its rough state as an example.

From Project Gutenberg