Assertion: mollusk's shell | /r/MadeOf | middle prismatic layer
Facets:
Source sentences:
text: The two shells, which consist of an outer organic layer, a middle prismatic layer, and a very smooth nacreous layer, are joined at the oldest part of the shell called the umbo.
text: The two shells, which consist of an outer organic layer, a middle prismatic layer, and a very smooth nacreous layer, are joined at the oldest part of the shell called the umbo.