It must be borne in mind that these fossils have, for the most part, been picked up by persons wholly uninstructed as to the characters which alone render such specimens interesting. What the waves cast up on the strand, the fishermen gather together, the casual visitor selects such as please his fancy, and the remainder are thrown away, or employed to pave the footpath, or surround the flower-border of the cottager's dwelling. * The remains hitherto found, are separate bones belonging to the well-known Wealden reptiles, viz. the Iguanodon, Hylaosaurus, Megalosaurus, and Streptospondylus; and the Cetiosaurus, Plesiosaurus,† and two or more kinds of turtles. I have seen but two teeth; a fragment of one belonging to the megalosaurus, and the specimen figured in lign. 27. THE IGUANODON.-Of this most gigantic of terrestrial reptiles, which, when living, must have more nearly resembled in its magnitude and huge proportions, the largest of our living pachydermata, than any of the saurian order to which it belongs, many vertebræ, portions of ribs, and bones of the extremities, have been discovered in the Wealden at Sandown Bay, and at Brook and Brixton. The vertebræ are invariably deprived of their processes; even the neural arch is in general destroyed, and the Iguanodon from the Isle of Wight," "Geological Transactions," vol. iii. new series. * The largest toe-bone of the iguanodon now in my possession was obtained from a row of stones placed round the flower plot of a cottage near Brixton. I much regret that my professional engagements have rendered it impossible for me to attempt to remedy the evil mentioned in the text. Having given a concise exposition of the osteological characters of these extraordinary beings in the “Medals of Creation,' (vol. ii. p. 684, ch. xvii. and xviii.) with full instructions for the collection of their remains, to that work I beg to refer the reader desirous of pursuing these inquiries. waterworn body, or centrum of the bone, alone remains. * The specimens are commonly permeated with pyrites, and, in consequence, are of great weight. The long bones of the limbs are for the most part mutilated, and but seldom have an articulating extremity so perfect as to indicate the individual bone. Some of the fragments, however, retain characters sufficiently recognisable, and have unquestionably belonged to reptiles of enormous size. I obtained from Sandown Bay the lower half of a tibia (large bone of the leg), having the extremity that articulates with the foot perfect; the circumference of this bone is four times that of a perfect tibia of a young iguanodon, which is one foot long when entire, its length must therefore have been nearly four feet. The corresponding thigh-bone, estimated from the relative proportions of a femur and tibia in juxtaposition, would be a foot longer: the entire length of the leg and thigh to which the Sandown fossil belonged, must consequently have been upwards of nine feet. : The most perfect femur, or thigh-bone, collected in the Isle of Wight, was dug out piecemeal from a fallen mass of the cliff in Brook Bay: it evidently belonged to an aged individual, and though squeezed and somewhat distorted by pressure while softened by long immersion in the clay in which it was imbedded, well displays the peculiar characters of this part of the skeleton of the iguanodon. It is 3 feet 4 inches in length. The figure in lign. 26 is a representation of this specimen, as it would appear if uncompressed. The femur of the Iguanodon is so remarkable, that even fragments may readily be distinguished; and as portions of this bone are not unfrequently to be met with in the clay cliffs or on the shore, I subjoin the following description. * As shown in lign. 138, fig. 8, p. 697, "Medals of Creation," vol. ii. The perfect form of a caudal vertebra of the Iguanodon is represented in fig. 3 of the same lignograph. The head is hemispherical, and projects inwards; a a laterally flattened process, or trochanter (lign. 26, a), forms the external boundary of the neck of the bone, from which it is separated by a deep and very narrow vertical fissure. The shaft is sub-quadrangular; a slightly elevated ridge, produced by the union of two broad, flat, longitudinal surfaces, extends down the middle of the anterior face, and diverg ing towards the inner condyle, gradually disappears. The shaft terminates below in two large rounded, and laterally compressed condyles (c, d), which are separated in front and behind by a deep groove (e). Near the middle of the shaft, the mesial, or inner edge, forms a compressed ridge, which extends into an angular projection, or inner trochanter (b). Thus the upper part of the femur may be known by the presence of the upper trochanter (a); and if that process is broken away, the fractured surface indicating its position will be detected. If a fragment of the middle part of the shaft e, Groove between the condyles. only is found, the flattened angular spaces, and the submedian trochanter (b), or the LIGN. 26.-LEFT FEMUR OF AN IGUA NODON. From Brook Bay. (The original, 40 inches in length.) a, Upper trochanter. mark of its attachment, will identify it. The lower extremity of the femur may be distinguished by the deep groove (e) between the condyles, both in front and behind. The long bones of the iguanodon have a large medullary cavity.* Several bones of the feet and toes have been found in this locality. Dr. Buckland obtained a toe-bone of enormous size from Sandown Bay; it is six inches long and fifteen inches in circumference, at the largest extremity.† The metatarsal and phalangeal bones of the iguanodon are short and thick, and so much resemble those of the hippopotamus, that Baron Cuvier at first supposed the specimens from Tilgate Forest belonged to that animal. TOOTH OF THE IGUANODON.-With the thigh-bone above described were found several dorsal and caudal vertebræ, many fragments of ribs, and the only tooth of the iguanodon I have obtained from the Island. It evidently, like the femur, belonged to an adult, and very probably to the same individual. The crown is worn down almost to the neck of the tooth, and shows the remarkable character imparted to the teeth of this herbivorous reptile, by the trituration of its food,—a character in which they differ from the teeth of any other known reptile, either living or extinct; for all other herbivorous reptiles chip off and swallow their food whole, the construction of their jaws not admitting of a grinding motion. From this condition of the crown, as shown in the tooth figured below, it is obvious that the iguanodon fed on vegetables, and masticated its food like the horse and other herbivorous mammalia: while the base shows the imprint of the successional tooth, which, "Medals of Creation," vol. ii. p. 748. "Geol. Trans." vol. iii. pl. 41. For an account of the development of the teeth of the Iguanodon, see "Fossils of Tilgate Forest," p. 72; and "Wonders of Geology," p. 390. TOOTH OF THE IGUANODON. 231 by its pressure, occasioned the absorption of the fang of the old one. In the perfect tooth, the crown is of a prismatic form, with three or four longitudinal ridges down the front, and a broad denticulated margin on each side.* The resemblance between the unworn teeth of the iguanodon and those of the iguana, a herbivorous lizard of the West Indies, suggested the name of this colossal extinct reptile; but the teeth of the iguana are very small, not exceeding in size those of the mouse. The Sections of the teeth are beautiful objects under the microscope, and show that the structure of the dentine, or tooth-ivory, is coarser than in other reptiles, and resembles that which characterises the teeth of the Sloth tribe. crown of the tooth is incrusted with an external coating of enamel, which is thick in front, and thin on the inner surface. In consequence of this disposition, and of the dentine being hardest in the anterior part, the grinding surface of * "Medals of Creation," p. 741. |