Assertion: sponge's skeleton | /r/HasProperty | tetraxonic siliceous spicules
Facets:
value: with four equal rays
type: OTHER
value: with derivatives
type: OTHER
Source sentences:
text: The skeleton, if present, is composed of tetraxonic siliceous spicules with four equal rays (called calthrops) and derivatives showing reduced (diods, triods) or proliferated rays (lophocalthrops).