Definition of periostracum in English:

periostracum

noun

Zoology
  • The outer horny or fibrous organic covering of the shell of a mollusc or brachiopod.

Origin

Mid 19th century; earliest use found in Philosophical Transactions of the Royal Society of London. From scientific Latin periostracum from peri- + ancient Greek ὄστρακον.

Pronunciation

periostracum

/ˌpɛrɪˈɒstrəkəm/