. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. 230 HISTORICAL PALEONTOLOGY. fore, with those of the preceding Triassic formation. The Ferns are very abundant, and belong partly to old and partly to new genera. The Cycads are also very abundant, and, on the whole, constitute the most marked feature of the Jurassic vegetation, many genera of this group being known {Ftej'O- phylhim, Otozamitcs, Zamites^ Crossozamia, Williainsonia, Buck- lafidia, &c.) The so-called "dirt-bed" of the Purbec
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. 230 HISTORICAL PALEONTOLOGY. fore, with those of the preceding Triassic formation. The Ferns are very abundant, and belong partly to old and partly to new genera. The Cycads are also very abundant, and, on the whole, constitute the most marked feature of the Jurassic vegetation, many genera of this group being known {Ftej'O- phylhim, Otozamitcs, Zamites^ Crossozamia, Williainsonia, Buck- lafidia, &c.) The so-called "dirt-bed" of the Purbeck series consists of an ancient soil, in which stand erect the trunks of Conifers and the silicified stools of Cycads of the genus Mantcl- //c? (fig. 160). The Conifer(B of the Jurassic are represented by. Fig. 160.—Blantellia {Cycadeoided) viegalophylla, a Cycad from the Purbeck "; Upper Oolites, England. various forms more or less nearly allied to the existing Aran- ca?'iiE; and these are known not only by their stems or branches, but also in some cases by their cones. We meet, also, with the remains of undoubted Endogenous plants, the most important of which are the fruits of forms allied to the existing Screw-pines {PandaiiecB), such as Fodoauya and Kaida- carpinn. So far, however, no remains of Palms have been found; nor are we acquainted with any Jurassic plants which could be certainly referred to the great " Angiospermous" group of the Exogens, including the majority of our ordinary plants and trees. Amongst animals, the Frotozoans are well represented in the Jurassic deposits by numerous Foraminifers and Sponges; as are the Ceeleiiierafes by numerous Corals. Remains of these last-mentioned organisms are extremely abundant in some of the limestones of the formation, such as tlie " Coral-rag" and the Great Oolite ; and the former of these may fairly be considered as an ancient "reef" "Wi^ Rugose Corals have not hit
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