Dictionary of Ichthyology  

ganoid scale = a non-overlapping or partially-overlapping scale, often rhomboidal in shape, with thick outer ganoine layer (enamel-like substance), a middle layer of dentine and an inner dermal, cosmine bony layer. Grows by addition of material above and below, e.g. in Lepisosteidae, Amiidae and Polypteridae. Lepisosteidae have lost the dentine layer. The scales of Lepisosteidae are called lepisosteoid scales as distinct from paleaoniscoid scales of Brachiopterygii.

Dried specimen, Lepisosteus osseus, Shirley's Bay, Ottawa. Photograph by Brian W. Coad.

Canadian Museum of Nature
www.briancoad.com