order, but belonging to several extinct genera, swarmed throughout the whole of the secondary and tertiary epochs. As the living crocodilians frequent fresh water, the remains of animals of this type indicate the existence of countries watered by streams and rivers, or abounding in lakes: but the modification of the spinal column, so prevalent in the ancient forms, may, perhaps, be referable to a marine rather than to a terrestrial condition of existence, in some of these extinct saurians.

27. ENALIOSAURIANS, or MARINE LIZARDS.*—Ichthyosaurus (Fish-like Lizard).-In the lias of the west of England, teeth, vertebræ, and other parts of the skeletons of reptiles, which were supposed to be related to the Crocodiles, had for many years excited attention; but until 1814, when a considerable collection, from Dorsetshire, formed by Mary Anning, was sold in London, no accurate investigation of these interesting relics had been attempted.† Subsequently a great number of skeletons have been found, numerous memoirs published, and the form and structure of the originals thoroughly investigated. Many beautiful specimens are figured and described in the splendid work of Mr. Hawkins, whose unrivalled collection of these remains is now deposited in the British Museum. The bones of reptiles so abundant in the Lias are chiefly referable to two genera; the one called Ichthyosaurus (by Mr. König), to denote its relation to fishes and reptiles; the other, Plesiosaurus (so named

* Medals, p. 663.

See No. I. of Charlesworth's "London Geological and Paleontological Journal," for an account of the sale of this collection.

"Memoirs of Ichthyosaur and Plesiosaur;" by Thomas Hawkins, folio, with Plates, 1838; and " Book of the Great Sea-dragons," folio, with Plates, 1840. Fully to realize the external form and general character of the Ichthyosauri and Plesiosauri, the student must visit the Crystal Palace Gardens, and make himself acquainted with Mr. Waterhouse Hawkins's life-sized models of these extinct sea-reptiles; smaller models of which also are obtainable for study in the cabinet.

by Mr. Conybeare), to indicate that it approached nearer than the animals of the other genus to the Lizards, or Saurians.

The Ichthyosaurus had the beak of a porpoise, the teeth of a crocodile, the head and sternum of a lizard, the paddles of a cetacean, and the vertebræ of a fish. This restoration (Lign. 134) shows its general configuration, as demonstrable from the skeleton; from the peculiarity of the terminal vertebræ of the tail, Prof. Owen concludes that the original had a strong vertical tail-fin.* There are many species, some of which are of a magnitude equal to that of young whales. The teeth are conical, sharp, and striated, resembling those of crocodiles in the power of reproduction, but differing in the number, situation, and mode of regeneration: one species

LIGN. 134.-RESTORED FIGURE OF THE ICHTHYOSAURUS.

has 110 in the upper, and 100 in the lower jaw; they are arranged in a deep furrow or groove, not in sockets, and were retained only by the integuments. The orbit is very large, and the sclerotic or outer coat of the eye is made up of thin bony plates, arranged round the central opening or pupil, as in the owl and other birds; a mechanism by which the power of the eye is materially increased, and vision adapted to near or remote objects at will. The bones forming the sternum, or chest, which protect the organs of respiration, are strong, and largely developed,† and the sternal arch offers a remarkable correspondence with that of the Ornithorhyncus of Australia.

* Geol. Trans. 2nd ser. vol. v. p. 511.

Medals, n. 667

Like turtles, the Ichthyosaurus had four paddles, composed of numerous bones enveloped in one fold of integument, so as to form an entire fin, as in the cetacea;* the fore-paddles are large, and in some species consist in one hundred bones (Lign. 135); the hinder pats are smaller, and contain but thirty or forty. The internal structure of these instruments therefore resembles that of the paws of turtles: and (as is even the case in the fin of the Porpoise) the same elements

FROM LYME REGIS.

Fig. 1. Left fore-paddle of the Ichthyosaurus.
Fig. 2. Left fore-paddle of the Plesiosaurus.
(One-eighth the natural size.)

of an arm are found as in the quadrupedal mammalia, vız. a humerus, radius, ulna, and phalanges. The nostrils, which in

* The soft integuments of the paddle are occasionally preserved: see the figure of a beautiful example from Barrow-on-Soar, Geol. Trans. 2nd ser. vol. vi. pl. 20, and Medals, p. 669.

Crocodiles are situated at the extremity of the beak or muzzle, are in the Enaliosauri placed, as in the Cetacea, beneath the orbits. The vertebræ are somewhat hourglass-shaped, but less so than in the sharks and other fishes; the spinal column admitted of the utmost freedom of motion, while in the neck the vertebræ connecting the head to the spinal column are anchylosed, and have supplementary bones to increase the strength, and diminish motion.* The general figure of the Ichthyosaurus must have been that of a Grampus or Porpoise, with four large paddles. The teeth prove it to have been carnivorous; the paddles, that it was aquatic; the scales, bones, and other remains of marine fishes constantly found in the abdominal cavities of the skeletons, and in the coprolites, that it was an inhabitant of the sea. Its skin appears to have been naked, or at least destitute of scales.‡

28. THE PLESIOSAURUS.§-The discovery of a remarkable specimen, by Miss Anning, enabled Mr. Coneybeare at once to establish the characters of that extraordinary extinct marine reptile, the Plesiosaurus, which differs from the Ichthyosaurus in the extreme smallness of the head, enormous length of the neck, and other osteological peculiar

* Memoir on a Peculiarity of Structure in the Neck of the Ichthyosaurus, by Sir P. M. de Grey Egerton. Geol. Trans. 2nd ser. vol. v. p. 187. + The Coprolites, or fossil excrements, of Ichthyosauri (the true nature of which was first ascertained by the sagacity of the late Dean of Westminster) are found in profusion in the clays and marlstones of the Lias; often occupying the abdominal cavity of the skeleton (see Dr. Buckland's Bridg. Treat., p. 190, pl. 15); and the state of preservation of these peculiar bodies is such, as to show not only the nature of the food of these reptiles, but also the dimensions, form, and structure of the stomach and intestinal canal. The coprolites of the fishes of the chalk often afford like indications. See above, p. 358; and Medals of Creation, p. 621.

See Buckland's Bridge

Relics of the skin occur in a fossil state. water Treatise, Plate 10, fig. A. 1, 2, 3, 4; Mr. Cole's paper on the skin of the Ichthyosaurus, Geol. Journal, vol. ix. p. 79; and Mr. C. Moore's remarks on the subject, Report Brit. Assoc., 1856, p. 69.

§ Medals of Creation, p. 671.

ities.* The neck, which in most animals is composed of five vertebræ, and in the extreme recent example, the Swan, does

LIGN. 136.-RESTORED FIGURE OF THE PLESIOSAURUS.

not exceed twenty-four, here consists of from twenty to forty; and its length is sometimes equal to that of the entire body and tail. This reptile combines in its structure the head of a lizard, with teeth implanted in sockets like the crocodile, -a neck resembling the body of a serpent,-a trunk and tail of the proportions of those of a quadruped,—with paddles like the turtle (Lign. 135, fig. 2). The vertebræ are longer and less concave than in the Ichthyosaurus, and the ribs, being connected by transverse abdominal processes, present a close analogy to those of the Chameleon.

The collection of Mr. Hawkins, now in the British Museum, contains a skeleton eleven feet long, and so nearly perfect, that the entire form of the original creature may be completely restored. The late Dean Coneybeare compared the Plesiosaurus to a turtle stripped of its shell, and thought it probable, from its long neck presenting considerable impediment to rapid progress in the water, that it frequented the coast, and lurked among the weeds in shallow water. As it is evident that it must have required frequent respiration, it probably swam on or near the surface, and darted down upon the small fishes on which it preyed.

Ichthyosaurs and Plesiosaurs have been found throughout the secondary strata, from the Lias to the Chalk inclusive; with the exception of the Wealden, in which no traces of

* In the sternum of the Plesiosaurus the coracoid bones bave their greatest development. Medals, p. 667, fig. 213.