In carefully examining, for purposes of restoration, some of the earliest ganoidal fishes, I was not a little impressed by the peculiar mechanical contrivances exhibited in their largely developed dermal skeletons. In some cases these contrivances were sufficiently simple, resembling those which we find exemplified in the humbler trades, originated in comparatively unenlightened ages; and yet their simplicity had but the effect of rendering the peculiarly _human_ cast of the mind exhibited in their production all the more obvious. The bony scales which covered fishes such as the Osteolepis and Diplopterus of the Old Red Sandstone, or the Megalichthys of the Coal Measures, were of considerable mass and thickness. They could not, compatibly with much nicety of finish, be laid over each other, like the thin horny scales of the salmon or herring; and so we find them curiously fitted together, not like slates on a modern roof, but like hewn stones on an ancient one. There ran on the upper surface of each, along the anterior side and higher end, a groove of a depth equal to half the thickness of the scale; and along the posterior side and lower end, on the under surface, a sort of bevelled chamfer, which, fitting into the grooves of the scales immediately behind and beneath it, brought their surfaces to the same line, and rendered the shining coverings of these strongly armed ganoids as smooth and even as those of the most delicately coated fishes of the present day. In the scales of the Celacanth family the arrangement was different. Though exceedingly massive in some of the genera, they were imbricated, like those of the Pangolins; and were chiefly remarkable for the combination of contrivances which they exhibited for securing the greatest possible amount of strength from the least possible amount of thickness. The scales of _Holoptychius giganteus_ may be selected as representative of those of the family to which it belonged. It consisted of three plates, or rather, like the human skull, of two solid plates, with a _diploe_ or spongy layer between. The outer surface was curiously fretted into alternate ridges and furrows; and hence the name of the genus,--_wrinkled scale_; and these imparted to the exterior plate on which they occurred, and which was formed of solid bone, the strength which results from a corrugated or fluted surface. Cromwell, in commissioning a friend to send him a helmet, shrewdly stipulated that it should be a "fluted pot;" and we find that the Holoptychius had got the principle of the fluted pot exemplified in the outer plate of each of its scales, untold ages before. The spongy middle plate must, like the diploe of the skull, have served to deaden the vibrations of a blow dealt from the outside. It was a stratum of sand bags piled up in the middle of a plank rampart. Their innermost table was formed, like the outer, of solid bone, but had a different arrangement. It was properly not one, but several tables, in