United States or Turkmenistan ? Vote for the TOP Country of the Week !
THE MISSISSIPPIAN SERIES. In the interior the Mississippian is composed chiefly of limestones, with some shales, which tell of a clear, warm, epicontinental sea swarming with crinoids, corals, and shells, and occasionally clouded with silt from the land. In the eastern region, New York had been added by uplift to the Appalachian land which now was united to the northern area.
In this Devonian section of our rocks we have proofs that the lands were extensively covered with forests of low fern trees, and we find the first trace of air-breathing animals in certain insects akin to our dragon-flies. In this stage of the earth's history the fishes grew constantly more plentiful, and the seas had a great abundance of corals and crinoids.
It was a very impressive sight for me to watch the movements of the creature, for it not only told of its own ways, but at the same time afforded a glimpse into the countless ages of the past, when these crinoids, so rare and so rarely seen nowadays, formed a prominent feature of the animal kingdom.
An imperfect intelligence, imperfectly taught, and this is the condition of our finite humanity, will certainly fail to keep all these laws perfectly. Disease is one of the penalties of one of the forms of such failure. Malformed specimens of Crinoids are known from the Triassic and Jurassic deposits.
Scorpions are found in this period both in Europe and in America. The limestone-making seas of the Silurian swarmed with corals, crinoids, and brachiopods. With the end of the Silurian period the AGE OF INVERTEBRATES comes to a close, giving place to the Devonian, the AGE OF FISHES.
Other forms, such as the crinoids, or sea lilies, elevate the breathing parts on top of tall stems of marvellous construction, which brings those vital organs at the level, it may be, of three or four feet above the zone of mud.
Some of these crinoids, as if impatient of their plant-like life and asserting their animal kinship, at last tear themselves free from their stem and float off, turn over, and thereafter live happily upon the bottom of the sea, roaming where they will, creeping slowly along and fulfilling the destiny of our imaginary daisy. And here a comparison comes suddenly to mind.
Crinoids are rare at the present time, but they grew in the greatest profusion in the warm Ordovician seas and for long ages thereafter. In many places the sea floor was beautiful with these graceful, flowerlike forms, as with fields of long-stemmed lilies.
The pentacrinites, the lowest of the echinoderms, have only one living representative in tropical America, where we find at the same time the highest and largest spatangi and holothuridae. Is this not quite a parallel case with the monkeys and pachyderms? for once crinoids were the only representatives of the class of echinoderms.
In consequence of the peculiar method of growth, the crinoids often escape the damage done by the disturbance of the bottom, and thus form limestone beds of remarkable thickness; sometimes, indeed, we find these layers composed mainly of crinoidal remains, which exhibit only slight traces of partings such as we have described, being essentially united for the depth of ten or twenty feet.
Word Of The Day