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Not for all the ganoid fish that ever swam, would a discreet historian dare to hazard even in secret an opinion about the value of Natural Selection by Minute Changes under Uniform Conditions, for he could know no more about it than most of his neighbors who knew nothing; but natural selection that did not select evolution finished before it began minute changes that refused to change anything during the whole geological record survival of the highest order in a fauna which had no origin uniformity under conditions which had disturbed everything else in creation to an honest-meaning though ignorant student who needed to prove Natural Selection and not assume it, such sequence brought no peace.
A drab colour like that of the skin of the common toad is given to them by the iron salts present in many oolitic rocks; those found in the wealden of the Isle of Wight are black. That the "toad-stones" mounted in ancient rings are really the teeth of a fish has been already recorded by the Rev. They undoubtedly are the palatal teeth of the fossil extinct ganoid fish Lepidotus.
Again, vast as is the number of undoubtedly Ganoid fossil Fishes, and great as is their range in time, a large mass of evidence has recently been adduced to show that almost all those respecting which we possess sufficient information, are referable to the same sub-ordinal groups as the existing Lepidosteus, Polypterus, and Sturgeon; and that a singular relation obtains between the older and the younger Fishes; the former, the Devonian Ganoids, being almost all members of the same sub-order as Polypterus, while the Mesozoic Ganoids are almost all similarly allied to Lepidosteus.
A few thousand feet, more or less, of limestone were the liveliest amusement to the ganoid, but they buried the uniformitarian alive, under the weight of his own uniformity.
They were of the Labyrinthodont family, and their association with the fish of the coal, of which so large a proportion are ganoids, reminds us that the living perennibranchiate amphibia of America frequent the same rivers as the ganoid Lepidostei or bony pikes. Slab of sandstone from the coal-measures of Pennsylvania, with footprints of air-breathing reptile and casts of cracks.
But the fishermen, the real fishermen, know better. The mud-fish, more properly the bowfin, is a small, dark-colored, ganoid fish which is so tough and will live under such discouraging circumstances that it would make ideal pickerel bait if the pickerel would have anything to do with it, but they will not.
There, unable in the narrow compass to turn, even to shift a numbing muscle of his lean old body, in all the constraint of a standing posture, he was held in the flexure of the rock like some of its fossils, as unsuspected as a ganoid of the days of eld that had once been imprisoned thus in the sediment of seas that had long ebbed hence, or the fern vestiges in a later formation finding a witness in the imprint in the stone of the symmetry of its fronds.
Owen was an accomplished lecturer; but one's attention to him depended on two things a primary interest in the subject, and some elementary acquaintance with it. If, for example, his subject were the comparative anatomy of the cycloid and ganoid fishes, the difference in their scales was scarcely of vital importance to one's general culture.
The Lepidosiren is also so closely allied to amphibians and fishes, that naturalists long disputed in which of these two classes to rank it; it, and also some few Ganoid fishes, have been preserved from utter extinction by inhabiting rivers, which are harbours of refuge, and are related to the great waters of the ocean in the same way that islands are to continents.
For instance, a single species of Trigonia, a great genus of shells in the secondary formations, survives in the Australian seas; and a few members of the great and almost extinct group of Ganoid fishes still inhabit our fresh waters. Therefore the utter extinction of a group is generally, as we have seen, a slower process than its production.
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