Ostracodermi

from The Century Dictionary.

• A sub order of plectognath fishes, represented only by the ostracionts or trunk-fishes, having the body covered with a solid coat of mail, no spinous dorsal fin, and teeth in the jaws. It contains only the family Ostraciontidæ, thus contrasted with the Sclerodermi and the Gymnodontes. See cut under cow-fish.
• Same as Ostracophori, but in that sense preoccupied.

from the GNU version of the Collaborative International Dictionary of English.

• proper noun plural (Zoöl.) A suborder of fishes of which Ostracion is the type.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun extinct group of armored jawless vertebrates; taxonomy is not clear