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Updated: May 14, 2025
We know that the dry land of the Trias absolutely teemed with reptiles of all groups except Pterodactyles, Snakes, and perhaps Tortoises; there is every probability that true Birds existed, and Mammalia certainly did. Of the inhabitants of the Permian dry land, on the contrary, all that have left a record are a few lizards.
And in the animals were of course included the birds the dove, for instance, grey with black wings, and the red-crested woodpecker or was it a hoopoe? and the insects, for there was a dear beetle, about the same size as the dove, that held its own with any of the mammalia.
But in bidding you good-bye, my dear little mammal, I could not bear to leave you under the weight of that debasing title: I wanted also to show you your greatness. Let us continue to pass in review the different orders of the class Mammalia. We may meet elsewhere with facts more important to science, but nowhere with any so personally interesting to ourselves.
The groups have, therefore, been subdivided into five classes, which we will study in succession, only naming each now: viz. mammals, birds, reptiles, fish, and batrachians. Do not alarm yourself at this last name: it is a Greek word, meaning simply frogs. The mammals are our immediate neighbors. Mammalia are the animals which produce milk.
The same moral is inculcated by the study of every other order of Tertiary monodelphous Mammalia. Each of these orders is represented in the Miocene epoch: the Eocene formation, as I have already said, contains Cheiroptera, Insectivora, Rodentia, Ungulata, Carnivora, and Cetacea.
Now the mammalia, whether terrestrial or aquatic, bear so small a proportion to other classes of animals, forming less, perhaps, than a thousandth part of a whole, that, if the longevity of species in the different orders were equal, a vast period must elapse before it would come to the turn of this conspicuous class to lose one of their number.
Beckles had determined thoroughly to explore the thin layer of calcareous mud from which in the suburbs of Swanage the bones of the Spalacotherium had already been obtained, and in three weeks he brought to light from an area forty feet long and ten wide, and from a layer the average thickness of which was only five inches, portions of the skeletons of six new species of mammalia, as interpreted by Dr.
I called attention in 1830 to the fact, which had not at that time attracted notice, that the association in the Post-pliocene deposits of shells, exclusively of living species, with many extinct quadrupeds betokened a longevity of species in the testacea far exceeding that in the mammalia.
I have already mentioned nearly all the mammalia common in this country. Of armadilloes three species occur, namely, the Dasypus minutus or pichy, the D. villosus or peludo, and the apar. The first extends ten degrees farther south than any other kind; a fourth species, the Mulita, does not come as far south as Bahia Blanca.
If the interpretation of the gigantic foot-steps in the colored sandstone of North America, as belonging to the cursorial birds, is correct, the first appearance of birds falls in the time between the reptilia and mammalia; otherwise the first mammalia would have appeared before the first birds.
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