sees in Pterodactyle an indication of the course that nature took in changing the reptilian organization to that of birds and mammals. The less important organs, those of motion, assimilate partly to those of the bird and partly to those of the bats, but always preserve the fundament reptile type and reptile number of bones. The skull, fluctuating in character between the monitor and crocodile, hides its reptile nature under the outer form of the bird, but retains the teeth. To change the skull into a bird's skull it would only be necessary that a few separate elements should be blended together, and that a few peculiar bones should be removed. The length of the neck, varying only in a few species, is a deviation from the reptile type, and indicates an approximation to the structure of 'the bird; but the number of the vertebræ remains constant notwithstanding the increased length. The fundamental plan of the crocodile may be recognised in all the important parts of the vertebræ. The body of the reptile, to be enabled to fly, would need a larger breast and a stronger structure of the fore-limbs. The shoulder-blade of the reptile, with its extremities forming the glenoid cavity, is necessarily smaller and prolonged backward, and altered to resemble that of a bird. The scapula only formed the back part of the glenoid cavity, but it is thick and strong, suggesting an affinity with the bats.

The breast-bone, in the form of a shield, is changing into that of a bird; as are the ribs, which are attached in a peculiar way to the vertebral column. It is really the strong sternum of the Chameleon, with moveable dorsal vertebræ. The whole chest is supported by the peculiar continuation of the wings of the pubic bones (Schambein). The ischiac and pubic bones resemble those of the Chameleon, but the ilium runs a little down, like that of a bird, and is only slightly connected with two sacral vertebræ, as in reptiles, prolonging itself a little upward and forward, as in mammals. The wings of the pubic bones exist in the Turtle and Monitor, but of small extent; they are also represented in the mammals by the upward development of the pubic bones in those families, genera, and species, in which nature has indicated by variety of shape, or peculiarities of development, or by affinities with reptiles, quite a new type and capacity for variation within certain limits, which is especially the case with certain Rodents and Opossums, and Monotremes. It would not be astonishing to find in Pterodactyles the marsupial bones. And indeed the Pterodactylus crassirostris has a small tongue-shaped bone, probably belonging to the pelvis. The less important part of the skeleton, the tail, is formed precisely as in mammals, and is identical with that of the bats. Both the thigh and shin are mammalian, and only the foot retains the same number of parts as in reptiles.

This animal was enabled by means of the pelvic bones and the long hind-legs to sit like the squirrels.

We should regard this position as natural but for the long wing-finger hanging far down the sides. If it were to creep along it would have the same difficulties as a bat, and the length and weight of the head, as well as the proportional weakness of the bind limb, make it improbable that they progressed by leaping. These animals made use of their claws only to hang on to rocks and trees and to climb up steep cliffs. They could fly with their wings, and keep themselves aloft in order to catch insects or sea animals. The wide throat and the weak and high supports of the jaw-bone make it probable that they only used their teeth to capture their prey and not to mince it. By means of their long neck, which they usually bore curved backward in order to keep their balance, they could stretch out their head to their prey and change their centre of gravity, and so fly in different positions. The fundamental type of the Crocodile and Monitor leads us to suspect that they had a skin covered with scales. The approximation to the shape of the Bird makes it probable that they were feathered. And the whole outline, similar to that of the Bat, leads to the supposition that they were covered with hair, like the Monotremes. Goldfuss thinks he has got a clear insight into the covering of the body and the whole condition of the wing in examining the Pt. crassirostris. And the soft state of the stone near the bones he attributes to the presence of the soft parts of the animal; and supposes that on the original folds of the wing-membrane are to be seen tufts and bunches of curved hair directed downward and sideway[G]. And on the principal slab he finds evidence that the Pterodactyle had a mane on the neck like a horse. The tufts on the counter slab have some similarity with the feathers of the ostrich. Some very tender impressions on both plates still more resemble feathers. He recognizes the outline and faint diverging rays of a bird's feather, but never sees a strong quill. The microscope, instead of making the image clearer, makes it, on the contrary, vanish, because then the rough parts become prominent. Also on the slab which contains the Pterodactylus medius[H], are seen numerous lines and fibres diverging like a bird's feathers. And on the upper part of the belly is the appearance of a scanty texture of hairs and feathers. The visible marks of two cylinders of the thickness of a quill, made of thin substance and filled with limestone, he would regard as quills if there were clearer marks of their feathers to be seen. As a note upon this von Meyer says, after examining the slabs, that the particles considered by Goldfuss to be hairs and feathers rest upon appearances not only to be seen in the vicinity of Pterodactyles, but which occur upon many other kinds of petrifactions that have nothing in common with the Pterodactyle; and that the roughnesses of the slab have nothing to do with the folds of the wing or the muscles.

[G] This is represented in Pl. 7, 8 of his memoir, loc. cit.

[H] Pl. 6, Nova Afta Acad. Leopold, Vol. XV. Pt. 1.

Wagner[I]

[I] Abhandl. Bayerischen Acad. 1852, Vol. VI.

is so convinced that the Pterodactyles are Amphibians approximating to the Saurians, that he does not think it necessary to go into any controversy in the matter; but he acknowledges that their forms sometimes present peculiarities of bird and mammal. The head especially shows a blending of the bird and reptile types. Its outline, particularly when seen from above, is that of a long-beaked water-bird. And the long interval between the nose-holes and the tip of the jaw, and the peculiar fact of a hole between the nose and eye-holes, and the want of the continuation of the coronoid of the lower jaw, rather resemble a water-bird than a Saurian. But the presence and the form of the teeth show it to be a Saurian; and not only the teeth, but the configuration of the whole back part of the skull, reproduces the type of the Monitor. The sclerotic circle is a peculiar mark of birds and saurians. Very peculiar, however, is the extremely short back part of the skull; and the articulation of the lower jaw, stretched far forward and united just under the middle of the eye-hole. The more or less long neck, which may assume the form of an S, deviates very much from the short stiff neck of reptiles, and is quite bird-like, the neck-vertebræ of which those of the Pterodactyle closely resemble in shape; while their constant number of seven reminds us of mammals and crocodiles. The neck has the same flexibility as in a bird. The short and weak trunk-vertebræ are in such disproportion to the length and strength of the neck-vertebræ as is never met with even in the birds and mammals which have the longest necks. The trunk-vertebræ are completely separated from each other, and may be divided into dorsal, lumbar, and sacral vertebræ. The transverse processes of the back-vertebræ are notched out like those of the crocodile. The tail is short in most species, and this is a deviation from the type of the Saurians, and an approximation to birds and to many mammals. But there are some kinds with very long tails, as is the case with mammals and usually with Saurians. But the vertebræ of these long-tailed Pterodactyles deviate very much from those of Saurians. And while the Saurian vertebræ are provided with long transverse processes and upper and lower spinous-processes (Dorn-Fortsätzen), they seem in the Pterodactyle to be almost devoid of processes and resemble those of mammals, on the tails of which these processes soon disappear. In a certain point of view we could say of the vertebral column of the Pterodactyle, that it has borrowed the neck from the bird, the trunk from the reptile, and the tail from the mammal. The ribs are connected to the transverse processes as in crocodiles, except with the atlas and axis. Quite in the type of the Saurians are the abdominal ribs, which are wanting to all birds and mammals, but often occur in the Lacertian order. The structure of the shoulder and breast-bone separate the Pterodactyle from the mammal, these parts being formed after the type of the Birds and Saurians, the characters of which are blended together. The small and elongated shoulder-blade, like the coracoid bone, belongs to the type of the bird rather than to that of the Saurians, of which, in reference to the last-named bone, only crocodiles have a similar one. The breast-bone, by its large expansion, points to the crocodiles, but at the same time, by the want of the keel, points to the ostrich-like birds, save that it is proportionally larger and wider than in these. The Pterodactyle, in common with the crocodile, wants the patella. The pelvis is formed on the type of the Saurians, although the ilium, by length and form, points somewhat to the mammals. The length and delicate form of the long bones of the limb, as well as the larger development of the fore-arm than of the upper-arm, and larger development of the lower thigh than of the upper thigh, and the thinness and elegance and shortness of the ?fibula (Wadenbein) have the characters of birds. The length of the middle hand [metacarpals] resembles that of birds, but its form in Pterodactyle is conformable to that of mammals. The first three fingers have the form and condition of the phalanges of lizards. The phalanges form the series 2, 3, and 4. The fourth, or air-finger, on the contrary, is of a peculiar type, of which no analogue is found in other animals, unless a somewhat similar arrangement be accredited to the bats. It is of enormous length, composed of four parts and without a claw. The hind-leg is, in proportion to the fore-leg, weak, and in general does not take the bird-form, but that of a Saurian. It has five toes, with unusual arrangement of the phalanges into the series 1, 5, 4, 3, 2. One toe has no nail, and the others have claws weaker than those of the hand. It can hardly be supposed that the animal lived in the water. All Saurians that live either in the water or on land are short-legged; it is the same with the swimming birds. But the Pterodactyle has its hind-legs as long as a land or air-bird; and as in these, the shin especially exceeds the length of the thigh. At the same time the toes, when they are in their natural position, were so close together that we may suppose the animal not to have been web-footed. The great development of the hand, by means of the long middle hand and especially of the enormous length of the air-finger, makes it probable that it was the chief organ of flight, as in birds and bats; also deviating in a peculiar manner from both these types, the long air-finger served to expand the wing-membrane, which extended from the upper part of the finger to the trunk, and which in all probability did not touch the hind-legs. This we infer from the circumstance that the animal, in a position with the organs of flight folded up, was not supported like the bat on its four feet, but stood upright on its hind-legs like a bird. Such a position presumes the same freedom in moving the hind extremities as with birds; only in such a position could the animal walk on without being hindered by its flying organs when they were folded up like those of a bird. Only in such an upright position could the animal keep upright its unusually long head with the long and strong neck and be kept in balance, the neck being able to take a sigmoid curve like that of a bird.

Wagner concludes: "By these means we have recognised in the Pterodactyle a Saurian, but of a habitude which greatly removes him from all others of his kind, and approximates him to birds. Excepting in ability to fly, he has nothing in common with the birds. The opinion 'that the animal is half crocodile half monitor disguised as a bird, but intending to be a bird,' is therefore not only a paradox but also false. With more truth, but less phantasy, we could say that the Pterodactyle was a Saurian in transition to the Birds."