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use of this disposition of the shortest joints in the middle of the toes of Lizards, is to give greater power of flexion for bending round, and laying fast hold on twigs and branches of trees of various dimensions, or on inequalities of the surface of the ground or rocks, in the act of climbing, or running.*

All these coincidences of number and proportion, can only have originated in a premeditated adaptation of each part to its peculiar office; they teach us to arrange an extinct animal under an existing family of reptiles; and when we find so many other peculiarities of this tribe in almost every bone of the skeleton of the Pterodactyle, with such modifications, and such only as were necessary to fit it for the purposes of flight, we perceive unity of design pervading every part, and adapting to motion in the air, organs which in other genera are calculated for progression on the ground, or in the water.

If we compare the foot of the Pterodactyle with that of the Bat, (see PI. 22, K,) we shall find that the Bat, like most other mammalia, has three joints in every toe, excepting the first, which has only two; still these two, in the Bat, are equal in length to the three bones of the other toes, so that the five claws of its foot range in one strait line, forming altogether the compound hook, by which the animal suspends itself in caves, with its head downwards, during its long periods of hybernation; the weight of its body being, by this contrivance, equally divided between each of the ten toes. The unequal length of the toes of the Pterodactyle must have rendered it almost impossible for its claws to range uniformly in line, like those of the Bat, and as no single claw could have supported for a long time the weight of the whole body, we may infer that the Pterodactyles did not suspend themselves after the manner of the Bats. The size and form of the foot, and also of the leg and thigh, show that they had the power of standing firmly on the ground, where, with their wings folded, they possibly moved after the manner of birds; they could also perch on tress, and climb on rocks and cliffs, with their hind and fore-feet conjointly like bats and Lizards.

same reasons that are assigned respecting the number of joints in the fifth finger. In the P. Longirostris, Curier considers the small bone, (PI. 21, 5. 6,) to be a rudimentary form of the fifth toe.

* A similar numerical disposition prevails also in the toes of birds, attended by similar advantages.

With regard to their food, it has been conjectured by Cuvier, that they fed on insects, and from the magnitude of their eyes that they may also have been noctivagous. The presence of large fossil Libellula?, or Dragon-flies, and many other insects, in the same lithographic quarries with the Pterodactyles at Solenhofen, and of the wings of coleopterous insects, mixed with bones of Pterodactyles, in the oolitic slate of Stonesfield, near Oxford, proves that large insects existed at the same time with them, and may have contributed to their supply of food. We know that many of the smaller Lizards of existing species are insectivorous: some are also carnivorous, and others omnivorous, but the head and teeth of two species of Pterodactyle, are so much larger and stronger than is necessary for the capture of insects, that the larger species of them may possibly have fed on fishes, darting upon them from the air after the manner of Sea Swallows and Solan Geese. The enormous size and strength of the head and teeth of the P. Crassirostris, would not only have enabled it to catch fish, but also to kill and devour the few small marsupial mammalia which then existed upon the land.

The entire range of ancient anatomy, affords few more striking examples of the uniformity of the laws, which connect the extinct animals of the fossil creation with existing organized beings, than those we have been examining in the case of the Pterodactyle. We find the details of parts which, from their minuteness should seem insignificant, acquiring great importance in such an investigation as we are now conducting; they show not less distinctly, than the colossal limbs of the most gigantic quadrupeds, a numerical coincidence, and a concurrence of proportions, which it seems impossible to refer to the effect of accident; and which point out unity of purpose, and deliberate design, in some intelligent First Cause, from which they were all derived. We have seen that whilst all the laws of existing organization in the order of Lizards, are rigidly maintained in the Pterodactyles; still, as Lizards modified to move like birds and Bats in the air, they received, in each part of their frame, a perfect adaptation to their state. We have dwelt more at length on the minutiae of their mechanism, because they convey us back into ages so exceedingly remote, and show that even in those distant eras, the same care of a common Creator, which we witness in the mechanism of our own bodies, and those of the myriads of inferior creatures that move around us, was extended to the structure of creatures, that at first sight seem made up only of monstrosities.

SECTION IX.

MEGALOSAURUS.*

The Megalosaurus, as its name implies, was a Lizard, of great size, of which, although no skeleton has yet been found entire, so many perfect bones and teeth have been discovered

* This genus was established by the Author, in a Memoir, published in the Geol. Trans, of London, (Vol. I., N. S. Pt. 2, 1824,) and was founded upon specimens discovered in the oolitic slate of Stonesfield, near Oxford, the place in which these bones have as yet chiefly occurred. Mr. Mantell has discovered remains of the same animal in the Wealden fresh-water formation of Tilgate Forest; and from this circumstance we infer that it existed during the deposition of the entire series of oolitic strata. The author, in

in the same quarries, that we are nearly as well acquainted with the form and dimensions of its limbs, as if they had been found together in a single block of stone.

From the size and proportions of these bones, as compared with existing Lizards, Cuvier concludes the Megalosaurus to have been an enormous reptile, measuring from forty to fifty feet in length, and partaking of the structure of the Crocodile and Monitor.

As the femur and tibia measure nearly three feet each, the entire hind-leg must have attained a length of nearly two yards: a metatarsal bone, thirteen inches long, indicates a corresponding length in the foot.* The bones of the thigh and leg are not solid at the centre, as in Crocodiles, and other aquatic quadrupeds, but have large medullary cavities, like the bones of terrestrial animals. We learn from this circumstance, added to the character of the foot, that the Megalosaurus lived chiefly upon the land.

In the internal condition of these fossil bones, we see the same adaptation of the skeleton to its proper element, which now distinguishes the bones of terrestrial, from those of aquatic Saurians.f In the Ichthyosauri and Plesiosaurf, whose paddles were calculated exclusively to move in water, even the largest bones of the arms and legs were solid throughout. Their weight would in no way have embarrassed their action in the fluid medium they inhabited; but in the huge Megalosaurus, and still more gigantic Iguanodon, which are shown by the character of their feet to have been fitted to move on land, the larger bones of the legs were diminished in weight, by being internally hollow, and having their cavities filled with the light material of

1826, saw fragments of a jaw, containing teeth, and of some other bones of Megalosaurus, in the museum at Besnncon, from the oolite of that neighbourhood.

* See Geol. Trans. 2d series, Vol. 3, p. 427, PI. 41.

t I learn from Mr. Owen that the long bones of land Tortoises have a close cancellous internal structure, but not a medullary cavity.

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marrow, while their cylindrical form tended also to combine this lightness with strength.*

The form of the teeth shows the Megalosaurus to have been in a high degree carnivorous: it probably fed on smaller reptiles, such as Crocodiles and Tortoises, whose remains abound in the same strata with its bones. It may also have taken to the water in pursuit of Plesiosauri and fishes.f

The most important part of the Megalosaurus yet found, consists of a fragment of the lower jaw, containing many

* The medullary cavities in the fossil bones of the Megalosaurus, from Stonesfield, are usually filled with calcareous spar. In the Oxford Museum there is a specimen from the Wealden fresh-water formation at Langton, near Tunbridge Wells, which is perhaps unique amongst organic remains: it presents the curious fact of a perfect cast of the interior of a large bone, apparently the femur of a Megalosaurus, exhibiting the exact form and ramifications of the marrow, whilst the bone itself has entirely perished. The substance of this cast is fine sand, cemented by oxide of iron, and its form distinctly represents all the minute reticulations, with which the marrow filled the intercoluminations of the cancelli, near the extremity of the bone. It exhibits also casts of the perforations along the internal parictes, whereby the vessels entered obliquely from the exterior of the bone, to communicate with the marrow. A mould of the exterior of the same bone has been also formed by the sandstone in which it was imbedded; hence although the bone itself has perished, we have precise representations both of its external form and internal cavities, and a model of the marrow that filled this femur, nearly as perfect as could be made by pouring wax into an empty marrow bone, and corroding away the bone with acid. The sand which formed this cast must have entered the medullary cavity by a fracture across the other extremity of the bone, which was wanting in the specimen.

From this natural preparation of ancient anatomy we learn that the disposition of marrow, and its connexion with the reticulated extremities of the interior of the femur, were the same in these gigantic Lizards of a former world, as in medullary cavities of existing species.

t Mr. Brodcrip informs me that a living Iguana (I. Tuberculata,) in the gardens of the Zoological Society of London, in the summer of 1834, was observed frequently to enter the water, and swim across a small pond, using its long tail as the instrument of progression, and keeping its fore-feet motionless.

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