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These insects, among which is a libellula, or dragon-fly, must have been blown out to sea, probably from the same land to which the pterodactyls, and other contemporaneous air-breathers, resorted. Tail and feather of Archaeopteryx, from Solenhofen, and tail of living bird for comparison. A. Caudal vertebrae of Archaeopteryx macrura, Owen; with impression of tail- feathers; one-fifth natural size.
Air-breathers of the American Coal. Changes of Condition of Land and Sea indicated by the Carboniferous Strata of Nova Scotia. The next group which we meet with in the descending order is the Carboniferous, commonly called "The Coal," because it contains many beds of that mineral, in a more or less pure state, interstratified with sandstones, shales, and limestones.
"Wait a minute!" protested Costigan, with a quick and furtive wink at his companions. "Do you expect us to go through water, and at this frightful depth?" "Certainly," replied the Nevian, in surprise. "You are air-breathers, of course, but you must be able to swim a little, and this slight depth but little more than thirty of your meters will not trouble you."
He classified animals as he found them; and, as a logician, he had a dichotomy for every difference which presented itself to his mind. At one time he divided animals into those with blood and those without, at another into the air-breathers and the water-breathers; into the wild and the tame, the social and the solitary, and so on in endless ways besides.
In many large coal-fields we continue as much in the dark respecting the invertebrate air-breathers then living, as if the coal had been thrown down in mid-ocean. The early date of the carboniferous strata can not explain the enigma, because we know that while the land supported a luxuriant vegetation, the contemporaneous seas swarmed with life with Articulata, Mollusca, Radiata, and Fishes.
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