Assertion: snail's shell | /r/MadeOf | chitin
Facets:
Source sentences:
text: This has a single, "limpet-like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate.
text: This has a single, "limpet-like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate, and is secreted by a mantle covering the whole upper surface.
text: Most shells that are found on beaches are the shells of marine mollusks, partly because these shells are usually made of calcium carbonate, and endure better than shells made of chitin.