Assertion: sand dollar's skeleton | /r/HasProperty | rigid
Facets:
Source sentences:
text: All sand dollars have a rigid skeleton known as a test.
text: All sand dollars have a rigid skeleton known as a test.
text: All sand dollars have a rigid skeleton known as a test.
text: Sand dollars has a rigid skeleton known as a "test", but these are not backbones
text: All sand dollars have a rigid skeleton called a “test” (no, not the kind you find in a classroom) and are covered in a skin of velvet-like spines, which help move them along the seabed.