The White Chalk Rock of Sussex has been rendered classical to the students of Geology by the skilful and laborious researches of the late Doctor Mantell. Previous to his time the Fish of the Chalk were known only by their teeth and bones, which abounded in every quarry. But he succeeded in bringing to light many whole skeletons, and disengaging them without injury from their chalky envelopment. In many cases these Fossil Fish appear to have suffered little from compression: the body still retains its rounded form; and even the most delicate scales and fins are as little disturbed or distorted as if the original had been surrounded by soft Plaster of Paris while floating in the water. For many years Doctor Mantell devoted himself, with indefatigable zeal, to the gathering of these interesting remains; and his magnificent collection now adorns the Galleries of the British Museum. In the annexed illustration is figured a specimen belonging to one of the most abundant species. It is closely allied to the common perch; and is popularly called Johnny Dory by the quarrymen of Sussex, but is entitled Beryx Lewesiensis by the learned.[75] [Illustration: Fig. 17.--Beryx Lewesiensis, from the Chalk, near Lewes.] From Fossil Fish we now turn to Fossil Reptiles. Many of our readers have, perhaps, heard or read something about an important group of rocks known by the name of the Lias. This formation is well developed in England, and has received much attention from Geologists. It stretches in a belt of varying width from Whitby on the coast of Yorkshire to Lyme Regis on the coast of Dorsetshire; passing in its course through the counties of Leicester, Warwick, Gloucester, and Somerset. It is composed chiefly of Limestone, Marl, and Clay; and is celebrated for the number and size of its great Fossil Reptiles. Of these the most remarkable is the Ichthyosaurus or Fish-like Lizard. This monster of the ancient seas combined, as its name denotes, the essential characters of a reptile with the form and habits of a fish. No such creature has been known to exist within historic times; nevertheless, all the various parts of its complicated structure have their analogies, more or less perfect, in the present creation. It had the head of a Lizard, the beak of a Porpoise, the teeth of a Crocodile, the back bone of a Fish, and the paddles of a Whale. In length it sometimes exceeded thirty feet; it had a short thick neck, an enormous stomach, a long and powerful tail. This last appendage, together with four great paddles or fins, constituted the chief organs of motion. But of all its parts the head was perhaps the most wonderful and characteristic. In the larger species the jaws were six feet long, and were armed with two rows of conical sharp-pointed teeth,--a hundred below, a hundred and ten above. The cavities in which the eyes were set measured often fourteen inches across, and the eyeballs themselves must have been larger than a man’s head.