The Jurassic epoch, next in succession, was a very important one in the history of Europe.  It completed the junction of several of the larger islands, filling the channel between the central plateau of France and the Belgian island, as well as that between the former and the island of Bretagne, so that France was now a sort of crescent of land holding a Jurassic sea in its centre, Bretagne and Belgium forming the two horns.  This Jurassic basin or inland sea united England and France, and it may not be amiss to say a word here of its subsequent transformations.  During the long succession of Jurassic periods, the deposits of that epoch, chiefly limestone and clays, with here and there a bed of sand, were accumulated at its bottom.  Upon these followed the chalk deposits of the Cretaceous epoch, until the basin was gradually filled, and partially, at least, turned to dry land.  But at the close of the Cretaceous epoch a fissure was formed, allowing the entrance of the sea at the western end, so that the constant washing of the tides and storms wore away the lower, softer deposits, leaving the overhanging chalk cliffs unsupported.  These latter, as their support were undermined, crumbled down, thus widening the channel gradually.  This process must, of course, have gone on more rapidly at the western end, where the sea rushed on with most force, till the channel was worn through to the German Ocean on the other side, and the sea then began to act with like power at both ends of the channel.  This explains its form, wider at the western end, narrower between Dover and Calais, and widening again at the eastern extremity.  This ancient basin, extending from the centre of France into England, is rich in the remains of a number of successive epochs.  Around its margin we find the Jurassic deposits, showing that there must have been some changes of level which raised the shores and prevented later accumulations from covering them, while in the centre the Jurassic deposits are concealed by those of the Cretaceous epoch above them, these being also partially hidden under the later Tertiary beds.  Let us see, then, what this inland sea has to tell us of the organic world in the Jurassic epoch.

At that time the region where Lyme-Regis is now situated in modern England was an estuary on the shore of that ancient sea.  About forty years ago a discovery of large and curious bones, belonging to some animal unknown to the scientific world, turned the attention of naturalists to this locality, and since then such a quantity and variety of such remains have been found in the neighborhood as to show that the Sharks, Whales, Porpoises, etc., of the present ocean are not more numerous and diversified than were the inhabitants of this old bay or inlet.  Among these animals, the Ichthyosauri (Fish-Lizards) form one of the best-known and most prominent groups.  They are chiefly found in the Lias, the lowest set of beds of the Jurassic deposits, and seem to have come in with the close