a horny covering, secreted as the outermost layer of most mollusk shells, that protects the underlying shell from erosion
Origin of periostracumModern Latin from Classical Greek peri-, around (see peri-) + ostrakon, a shell: see ostracize
The tough horny or fibrous outer covering of the shell of many mollusks and brachiopods.
Origin of periostracumNew Latin peri- Greek ostrakon shell ; see ost- in Indo-European roots.
- (malacology) The proteinaceous outer sheath of many molluscan shells.
Literally "surrounding shell," from peri- +"Ž ostracum.