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Among the Echinoderms we find that the Cystids and Blastoids have gone, and the sea-lilies reach their climax in beauty and organisation, to dwindle and almost disappear in the last part of the Mesozoic. One Jurassic sea-lily was found to have 600,000 distinct ossicles in its petrified frame. The free-moving Echinoderms are now in the ascendant, the sea-urchins being especially abundant.
The rocks which are composed of their remains show that vast areas of the sea-floor must have been covered with groves of sea-lilies, bending on their long, flexible stalks and waving their great flower-like arms in the water to attract food. With them there is now a new experiment in the stalked Echinoderm, the Blastoid, an armless type; but it seems to have been a failure.
Then on the foraminifera, which secretes a shell of lime from the water. Then on a step higher to the polycystina, which secretes a shell, or skeleton of flint-like material from the water. Then come the sponges. Then the coral-animals, anemones and jelly-fish. Then come the sea-lilies, star-fish, etc. Then the various families of worms. Then the crabs, spiders, centipedes, insects.
As these in turn are crushed, the more highly organised Malacostraca take the lead, and primitive specimens of the shrimp and lobster make their appearance. The Echinoderms are still mainly represented by the sea-lilies.
Small forests of these sea-lilies adorn the floor of the Silurian ocean, and their broken and dead frames form whole beds of limestone. The primitive Cystids dwindle and die out in the presence of such powerful competitors. Of 250 species only a dozen linger in the Silurian strata, though a new and more advanced type the Blastoid holds the field for a time.
Semi-tropical vegetation is found in Spitzbergen and the Antarctic, as well as in North Europe, Asia, and America, and in Australasia; corals and sea-lilies flourish at any part of the earth's surface. Warm, dank, low-lying lands, bathed by warm oceans and steeped in their vapours, are the picture suggested as we shall see more closely to the minds of all geologists.
It is the age of the Crinoids or sea-lilies. The starfish, which has abandoned the stalk, does not seem to prosper as yet, and the brittle-star appears. Their age will come later. It is precisely the order of appearance which our theory of their evolution demands.
Right in the midst of another plot of thick, flat leaves rises a mass of pink sea-lilies, and they are beautiful; but do examine the next bed of leaves. Are they not curious? A thick, hollow-looking stem goes through the middle of them, and on one side of the stem they are a deep pink, on the other side, yellow. Here are flowers shaped like horns and trumpets.
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