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Among Vertebrates there is no ordinally distinct fossil fish: there is only one extinct order of Amphibia the Labyrinthodonts; but there are at least four distinct orders of Reptilia, viz. the Ichthyosauria, Plesiosauria, Pterosauria, Dinosauria, and perhaps another or two.
Hermann von Meyer, again, to whose luminous researches we are indebted for our present large knowledge of the organization of the older Labyrinthodonts, has proved that the Carboniferous Archegosaurus had very imperfectly developed vertebral centra, while the Triassic Mastodonsaurus had the same parts completely ossified.
Among Vertebrates there is no ordinally distinct fossil fish: there is only one extinct order of Amphibia the Labyrinthodonts; but there are at least four distinct orders of Reptilia, viz. the Ichthyosauria, Plesiosauria, Pterosauria, Dinosauria, and perhaps another or two.
But the most remarkable examples of progressive modification of the vertebral column, in correspondence with geological age, are those afforded by the Pycnodonts among fish, and the Labyrinthodonts among Amphibia.
Now, however, it is considered probable that the soft back-boned Labyrinthodont Archegosaurus, was an immature or larval form, while Labyrinthodonts with completely developed vertebræ have been found to exist amongst the very earliest forms yet discovered.
Does not any such supposition become in the highest degree improbable, when, in the terrestrial or fresh-water Labyrinthodonts, which lived on the land of the Carboniferous epoch, as well as on that of the Trias, we have evidence that one form of terrestrial life persisted, throughout all these ages, with no important modification?
Or, if we go back to the older half of the Mesozoic epoch, how truly surprising it is to find every order of the Reptilia, except the Ophidia, represented; while some groups, such as the Ornithoseclida and the Pterosauria, more specialised than any which now exist, abounded. I refer to the Labyrinthodonts.
Among Vertebrates there is no ordinally distinct fossil fish: there is only one extinct order of Amphibia the Labyrinthodonts; but there are at least four distinct orders of Reptilia, viz. the Ichthyosauria, Plesiosauria, Pterosauria, Dinosauria, and perhaps another or two.
For anything that, as yet, appears to the contrary, the earliest known Marsupials may have been as highly organised as their living congeners; the Permian lizards show no signs of inferiority to those of the present day; the Labyrinthodonts cannot be placed below the living Salamander and Triton; the Devonian Ganoids are closely related to Polypterus and to Lepidosiren.
No evidence of past existence of minutely intermediate forms when such might be expected a priori. Bats, Pterodactyles, Dinosauria, and Birds. Ichthyosauria, Chelonia, and Anoura. Horse ancestry. Labyrinthodonts and Trilobites. Two subdivisions of the second relation of species to time.
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