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 of the Triassic epoch. It is greatly to be
regretted that all that is known of the Triassic Reptiles antecedent to
the Ichthyosauri