Meanings
nounperiostracum (plural periostraca or periostracums)
plural periostraca · plural periostracums
- biologyThe proteinaceous outer sheath of many molluscan shells.
Origin
Literally "surrounding shell", from peri- + ostracum.
Full word history & related roots →Cite this entry
APA
periostracum. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/periostracum
MLA
“periostracum.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/periostracum. Accessed November 4, 2026.
Chicago
WatkinsX Dictionary, s.v. “periostracum,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/periostracum.
Source: periostracum on Wiktionary, CC BY-SA 4.0.