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For instance, we consider the evidence of the Jurassic age of the Ichnolitic strata of the sandstone of the Connecticut River too strong to allow of their being any longer classed among the Triassic. We certainly differ from him in much that is said upon the subject of Man, as of one species. Yet we do not care to dwell upon these points, especially the latter.
By reference to the tables given at the end of the last chapter the reader will see that when the fossiliferous rocks are arranged chronologically, we have first to consider the Post-tertiary and then the Tertiary or Cainozoic formations, and afterwards to pass on to those of older date. Laurentian. 2. Cambrian. 3. Silurian. 4. Devonian. 5. Carboniferous. 6. Permian. 7. Triassic. 8. Jurassic. 9.
The great order of Reptiles made its advent in the Permian, culminated in the Triassic and Jurassic, and began to decline in the Cretaceous. The advance from the amphibian to the reptile was a long forward step in the evolution of the vertebrates. In the reptile the vertebrate skeleton now became completely ossified. Gills were abandoned and breathing was by lungs alone.
The predominance in earlier ages of these mammalia of a low grade, and the absence, so far as our investigations have yet gone, of species of higher organisation, whether aquatic or terrestrial, is certainly in favour of the theory of progressive development. Line of Separation between Mesozoic and Palaeozoic Rocks. Distinctness of Triassic and Permian Fossils. Term Permian.
Could we have been permitted to gaze upon the earth in the middle geologic period, in Jurassic or Triassic times, we should have seen it teeming with huge, uncouth, gigantic forms of animal life, in the sea, on the land, and in the air, and with many lesser forms, but with no sign of man anywhere; ransack the earth from pole to pole and there was no sign or suggestion, so far as we could have seen, of a human being.
But as the cold of the Permian yielded to a genial climate and rich vegetation in the course of the Triassic, the reptiles entered upon their memorable development. The amphibia were now definitely ousted from their position of dominance. The increase of the waters had at first favoured them, and we find more than twenty genera, and some very large individuals, of the amphibia in the Triassic.
The genera Saurichthys, Hybodus, and Gyrolepis are found in both these breccias, and one of the species, Saurichthys Mongeoti, is common to both bone-beds, as is also a remarkable reptile called Nothosaurus mirabilis. The saurian called Belodon by H. von Meyer, of the Thecodont family, is another Triassic form, associated at Diegerloch with Microlestes.
I conceive Australia to have become separated from the continent as early as the end of the Triassic epoch, or not much later.
The enormous expansion of the sea a great authority, Neumayr, believes that it was the greatest extension of the sea that is known in geology and lowering of the land would of itself tend to produce this condition, and it may be that the very considerable volcanic activity, of which we find evidence in the Permian and Triassic, had discharged great volumes of carbon-dioxide into the atmosphere.
And, in speculating upon the origin of a given group, he rarely goes further back than the "Ante-period," which precedes that in which the remains of animals belonging to that group are found. Thus, as fossil remains of the majority of the groups of Reptilia are first found in the Trias, they are assumed to have originated in the "Antetriassic" period, or between the Permian and Triassic epochs.
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