Assertion: oyster's shell | /r/MadeOf | valve
Facets:
Source sentences:
text: They have a hard calcareous shell made of two parts or 'valves'.
text: The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves.
text: Gastropods have a shell made of only one valve and it is usually coiled.
text: Oysters are bivalves, which means that its shell is made of two parts, or valves.