Ga·noi·de·i n. pl.  Zool. One of the subclasses of fishes. They have an arterial cone and bulb, spiral intestinal valve, and the optic nerves united by a chiasma. Many of the species are covered with bony plates, or with ganoid scales; others have cycloid scales.
  Note: ☞ They were numerous, and some of them of large size, in early geological periods; but they are represented by comparatively few living species, most of which inhabit fresh waters, as the bowfin, gar pike, bichir, Ceratodus, paddle fish, and sturgeon.
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  Ganoidei
       n : a group of mostly extinct primitive bony fishes
           characterized by armor-like bony scales [syn: order
           Ganoidei]