Assertion: sea urchin's shell | /r/AtLocation | beach
Facets:
Source sentences:
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.
text: Apart from mollusk shells, other shells that can be found on beaches are those of barnacles, horseshoe crabs and brachiopods.