The Collaborative International Dictionary of English v.0.48:

Hyalospongia \Hy`a*lo*spon"gi*a\, n. pl. [NL., fr. Gr. "y`alos
   glass + ? a sponge.] (Zool.)
   An order of vitreous sponges, having glassy six-rayed,
   siliceous spicules; -- called also Hexactinellin[ae].
   [1913 Webster]