The lias of the valley of Lyme Regis, Dorsetshire, is the chief grave-yard of the Ichthyosaurus platyodon; but its remains are pretty widely distributed. They have been found in the lias of Glastonbury, of Bristol, of Scarborough and Whitby, and of Bitton, in Gloucestershire; some vertebræ, apparently of this species, have likewise been found in the lias at Ohmden, in Germany.
No. 13.—Ichthyosaurus tenuirostris.
Behind the Ichthyosaurus platyodon, is placed the restoration of the Ichthyosaurus tenuirostris, or Slender-snouted Fish-lizard. The most striking peculiarity of this species is the great length and slenderness of the jaw-bones, which, in combination with the large eye-sockets and flattened cranium, give to the entire skull a form which resembles that of a gigantic snipe or woodcock, with the bill armed with teeth. These weapons, in the present species, are relatively more numerous, smaller, and more sharply pointed than in the foregoing, and indicate that the Ichthyosaurus tenuirostris preyed on a smaller kind of fish. The fore-paddles are larger than the hind ones. In the museum of the Philosophical Institution, at Bristol, there is an almost entire skeleton of the present species which measures thirteen feet in length. It was discovered in the lias of Lyme Regis. Portions of jaws and other parts of the skeletons of larger individuals have been found fossil in the lias near Bristol, at Barrow-on-Soar, in Leicestershire, and at Stratford-on-Avon. The Ichthyosaurus tenuirostris has also left its remains in the lias formation at Boll and Amburg, in Wirtemberg, Germany.
No. 14.—Ichthyosaurus communis.
Of this species, which was the most “common,” when first discovered in 1824, but which has since been surpassed by other species in regard to the known number of individuals, the head is restored, as protruded from the water, to the right of the foregoing species.
The Ichthyosaurus communis is characterised by its relatively large teeth, with expanded, deeply-grooved bases, and round conical furrowed crowns; the upper jaw contains, on each side, from forty to fifty of such teeth. The fore-paddles are three times larger than the hind ones. With respect to the size which it attained, the Ichthyosaurus communis seems only to be second to the Ichthyosaurus platyodon. In the museum of the Earl of Enniskillen, there is a fossil skull of the Ichthyosaurus communis which, measures, in length, two feet nine inches, indicating an animal of at least twenty feet in length.
Plesiosaurus.
The discovery of this genus forms one of the most important additions that geology has made to comparative anatomy. Baron Cuvier deemed “its structure to have been the most singular, and its characters the most monstrous, that had been yet discovered amid the ruins of a former world.” To the head of a lizard it united the teeth of a crocodile, a neck of enormous length, resembling the body of a serpent, a trunk and tail having the proportions of an ordinary quadruped, the ribs of a chameleon, and the paddles of a whale. “Such,” writes Dr. Buckland, “are the strange combinations of form and structure in the Plesiosaurus, a genus, the remains of which, after interment for thousands of years amidst the wreck of millions of extinct inhabitants of the ancient earth, are at length recalled to light by the researches of the geologist, and submitted to our examination, in nearly as perfect a state as the bones of species that are now existing upon the earth.” (Op. cit., vol. v. p. 203).
The first remains of this animal were discovered in the lias of Lyme Regis, about the year 1823, and formed the subject of the paper by the Rev. Mr. Conybeare (now Dean of Llandaff), and Mr. (now Sir Henry) De la Beche, in which the genus was established and named Plesiosaurus (from the Greek words, plesios and sauros, signifying “near” or “allied to,” and “lizard”), because the authors saw that it was more nearly allied to the lizard than was the Ichthyosaurus from the same formation.
The entire and undisturbed skeletons of several individuals, of different species, have since been discovered, fully confirming the sagacious restorations by the original discoverers of the Plesiosaurus. Of these species three have been selected as the subjects of Mr. Waterhouse Hawkins’s reconstructions and representations of the living form of the strange reptiles.