Source : Webster's Revised Unabridged Dictionary (1913)

Placoganoidei \Plac`o*ga*noi"de*i\, n. pl. [NL., fr. Gr. ?, ?, a
   tablet + NL. ganoidei. See {Ganoidei}.] (Zo["o]l.)
   A division of ganoid fishes including those that have large
   external bony plates and a cartilaginous skeleton.