Glass-sponge

from The Collaborative International Dictionary of English v.0.48

Glass-sponge \Glass"-sponge`\, n. (Zool.)
   A siliceous sponge, of the genus {Hyalonema}, and allied
   genera; -- so called from their glassy fibers or spicules; --
   called also {vitreous sponge}. See {Glass-rope}, and
   {Euplectella}.
   [1913 Webster]