Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/209

 relations of Fishes; the scales forming a kind of external skeleton, analogous to the crustaceous or horny coverings of Insects, to the feathers of Birds, and the fur of Quadrupeds, which shows more directly than the internal bones, their adaptation to the medium in which they lived.

A further advantage arises from the fact that the enamelled condition of the scales of most Fishes, which existed during the earlier geological epochs, rendered them much less destructible than their internal skeleton; and cases frequently occur where the entire scales and figures of the Fish are perfectly preserved, whilst the bones within these scales have altogether disappeared; the enamel of the scales being less soluble than the more calcareous material of the bone. VOL. I