The _plants_ of the Jurassic period consist principally of Ferns, Cycads, and Conifers--agreeing in this respect, therefore, 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 (_Pterophyllum, Otozamites, Zamites, Crossozamia, Williamsonia, Bucklandia,_ &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 _Mantellia_ (fig.160). The _Coniferoe_ of the Jurassic are represented by various forms more or less nearly allied to the existing _Araucarioe_; 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 (_Pandaneoe_), such as _Podocarya_ and _Kaidacarpum_. 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 _Protozoans_ are well represented in the Jurassic deposits by numerous _Foraminifers_ and _Sponges_; as are the _Coelenterates_ by numerous _Corals_. Remains of these last-mentioned organisms are extremely abundant in some of the limestones of the formation, such as the "Coral-rag" and the Great Oolite; and the former of these may fairly be considered as an ancient "reef." The _Rugose Corals_ have not hitherto been detected in the Jurassic rocks; and the "_Tabulate Corals_," so-called, are represented only by examples of the modern genus _Millepora_. With this exception, all the Jurassic Corals belong to the great group which predominates in recent seas (_Zoantharia sclerodermata_); and the majority belong to the important reef-building family of the "Star-corals" (_Astroeidoe_). The form here figured (_Thecosmilia annularis_, fig. 161) is one of the characteristic species of the Coral-rag. [Illustration: Fig. 161.--_Thecosmilia annularis_, Coral-rag, England.] [Illustration: Fig. 162.--_Pentacrinus fasciculos_, Lias. The left-hand figure shows a few or the joints of the column; the middle figure shows the arms, and the summit of the column with its side-arms; and the right-hand figure shows the articulating surface of one of the column-joints.]