From The Collaborative International Dictionary of English v.0.48 [gcide]:
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]