epth 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
each of which the osseous fibres, spread out in the general plane of
the scale, lay at a diverse angle from those of the table immediately in
contact with it. The principle was evidently that of the double-woven
cloth, or cloth of two incorporated layers, such as _moleskin_, in
which, from the arrangement of the threads, what a draper would term the
_tear_ of the one layer or fold lies at a different angle in the general
fabric from that of the other. We are thus presented, in a single fossil
scale little more than the eighth part of an inch in