The Collaborative International Dictionary of English v.0.48:

Silicoidea \Sil`i*coi"de*a\, n. pl. [NL. See Silex, and
   -oid.] (Zool.)
   An extensive order of Porifera, which includes those that
   have the skeleton composed mainly of siliceous fibers or
   spicules.
   [1913 Webster]