glass-rope

from The Century Dictionary.

• noun The stem of a glass-sponge, as Hyalonema.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A remarkable vitreous sponge, of the genus Hyalonema, first brought from Japan. It has a long stem, consisting of a bundle of long and large, glassy, siliceous fibers, twisted together.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A vitreous sponge of the genus Hyalonema, with a long stem, consisting of a bundle of long glassy siliceous fibres twisted together.