OSTEOLOGICAL COLLECTION

[D]Isis, 1818, p. 551.

Oken reasoned carefully so far as his materials went. He dwells much on the analogy of the wing to that of a bat, and seems to suspect that the marsupial bones would hereafter befound; and, excepting the head, finds that the other parts of the skeleton have their corresponding bones among mammals.

Afterwards, when he saw the specimens at Munich, he was so much struck at finding the quadrate bone of Lacertian form, though Sömmerring could not detect it even with a microscope, that he is shaken in his mammalian faith, and inclines to consider the animal a reptile.

Wagler[E].

[E]System der Amphibien, 1830, p. 75.

Wagler was impressed with the resemblance of the jaws and the rounded back part of the skull to those of Dolphins, and so far as the head went conceives it to have had nothing in common with Lizards. He recognizes mammalian characters in the pelvis and sternum, and fails, like Sömmerring, to detect a quadrate bone, and finds the sum of the characters like those of other extinct animals, such as Ichthyosaurus and Plesiosaurus, suggesting for it a position between mammals and birds. He supposed it unable to fly, that it never left the water, but swam about on the surface like a swan, and sought its food on the sea-bottom. He imagined the long arms to have been used after the fashion of turtles and penguins to row the body along; while to the claws he attributes the function of holding the females in the generative process.

Goldfuss[F].

[F]Nova Acta Acad. Leopold., 1831, Vol.XV.Pt.I.p. 103.

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 ofthe 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 thebind 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 Goldfussto 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. Butthere 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 fourparts 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."

Quenstedt[J].

[J]Ueber Pterodactylus Suevicus.Tubingen 1855.

In the long thigh, with the long neck, Quenstedt sees evidence that the animal was able to walk upright, being probably still more upright than birds, since the great disproportion between the neck on the one hand, and the thigh on the other, could not have allowed a more appropriate position. At the same time he makes a question, Did it go on four feet? But a little later, in his book,Sonst und Jetzt, 1856, he gives a sketch of the animal resting on its four legs; and remarks, "The position upon four feet is however hypothetical, but is probable. It had its wings folded back. The slightly curved and thin bones of the middle hand probably served to support the flying-membrane, and had therefore the same function as the spur-bone in the bats." Finally, he says in his book,der Jura, p. 813, "Perhaps this animal walked from time to time on four legs, being then supported by the fore-end of the metatarsal bone."

Burmeister[K].

[K]Beleuchtung uniger Pterodactylus arten.1855.

entirely rejects Quenstedt's opinions with regard to their upright position. He makes the following remarks: 'The animal walked on the free fore-toes and bore the wings like a bat, though with the body not in an upright position like a bird, but four-footed. The hind-foot is much too small for such an upright position, and the fore-foot much too strongly developed. I therefore believe that the Pterodactyle could much better have walked four-footed than a bat, because it possessed so much better developed fore-feet.' In the length of the tibia Burmeister sees no reason for the upright position, but, as he says, only a means for the wide expansion of the flying-membrane;—and an endeavour in walking on four feet to bring the leg into the necessary harmony with the arm, which is so much elongated with the flat-hand.

Hermann von Meyer[L].

[L]Fauna der Vorwelt. Reptilien aus dem Lithographischen schiefer.Frankfurt am Main. 1859. pp. 15-23.

The skull of the Pterodactyle can only be compared with thoseof birds and lizards. The form is essentially Avian, and the sutures are indistinct or obliterated as in birds, while in reptiles they are persistent The temporal bone enters into the formation of the reservoir for the brain, which is eminently characteristic of birds and quite different from anything found in lizards. The snout resembles a bird in being chiefly formed by the intermaxillary bone, which bounds the front of the anterior nares; and, as in birds, the bone extends backward between the eye-cavities to the frontal bone. The corresponding intermaxillary ridge of the Monitor is of less extent.

The frontal-bone forms the highest part of the skull, and is similar to that of birds. The principal frontal is double, and forms the upper and hind part of the cavity for the eye, and covered the greater part of the large brain, composed of two hemispheres, in which Oken long ago saw a similarity to the higher animals. The arched form of the back part of the skull is bird-like. The double parietal adjoins the principal frontal, and is conditioned like the parietal in birds. The supra-occipital is single as in birds, expanded, and forms the part of the skull which extends furthest back. From the form of the back part of the skull it may be concluded that the foramen magnum was situated as in birds, and that the head and neck were moved as in birds, and not as in reptiles and mammals.

The temporal bone rests upon the parietal and frontal, and forms much of the temporal foss. Its anterior border does not appear to enter into the margin of the orbital cavity as in birds, but seems to be replaced by the post-frontal, which resembles that of the Chameleon. Its hindmost branch, which can hardly be supposed to be the jugal, forms the outer boundary of the temporal foss by uniting with a process which is probably part of the mastoid. A similar closing of the cavity for the temporal muscles is also to be found in birds. The jugal and maxillary do not follow the bird type. The jugal consists of a single bone which forms the greater part of the anterior and inferior boundary of the cavity of the eye, which is surrounded with bones, as in Dragons and Iguana. In those birds in which the cavity of the eye is surrounded with bones the jugal does not enter into it. As in lizards, at its upper end the jugal is commonly connected with the lachrymal, which bone is like that of a bird.A bone, which appears to be the pre-frontal, enters into the back of the nasal aperture.

The nostril is double and often of large size.

The perforation in the skull between the orbit and nares is bird-like.

The quadrate bone is not quadratic as in birds, but cylindrical and shaft-like, as in the Chameleon. The articulation of the quadrate with the lower jaw is placed further forward than in birds and reptiles. The lower jaw, but for the teeth, has great similarity with that of a bird. Among reptiles its nearest resemblance is with Chameleons and Turtles. The hyoid is more bird-like than reptile-like.

Ribs and vertebræ.

It is uncertain whether the Pterodactyle had lumbar vertebræ. If they are wanting, therein the animals resemble birds, of which we are reminded in the short and stiff back and moveable neck. Pterodactyles possess a smaller number of neck-vertebræ and a larger number of back-vertebræ than birds. The long neck-vertebræ are paralleled by those of water-birds, by the Giraffe, the Camel, Protosaurus and Tanystrophæus. There are 7 cervical vertebræ, the 1st very short, 2nd not longer, but rather shorter than those which follow. There are in Pterodactyles from 12 to 16 dorsal vertebræ, while birds have never more than 11. It is not certain whether all Pterodactyles have an os sacrum; most have it, and therein resemble Mammals, Birds, and some fossil Saurians. In Pterodactylus dubius and P. grandipelvis and P. Kochi there are 5 or 6 vertebræ in the sacrum. In birds the sacral vertebræ vary from 5 to 22; in bats the number is from 5 to 6.

The short tails of Pterodactyles are more like those of mammals than birds; they include from 10 to 15 tail-vertebræ. In birds there are from 6 to 10 tail-vertebræ. Rhamphorhynchus has 38-40 tail-vertebræ, secured between thread-bones like those in the tail of rats.

The dorsal ribs are reptile-like. In herbivorous mammals and birds they are broader. A few species have the first pair of ribs large. The abdominal ribs belong neither to birds nor mammals, but are reptilian. In Rhamphorhynchus Gemmingi there are 6 pairs of sternal ribs.

The sternum

is bird-like, somewhat resembling lizards. It consists of a simple flat bone, but without the keel of a bird's sternum. It is relatively smaller than in birds, is broader than long, and therefore comparable with Struthious birds. They were not able flyers, since the part to which the muscles for flight should be affixed is wanting. And for the same reason they could not have been wandering animals. But Moles possess a keel on the breast-bone, which therefore is no evidence of flight. And in swimming-birds which do not fly the keel is much developed; and in swimming-birds the sternum is also long, so that neither length nor keel prove flight. So far as the evidence from the sternum goes, they were neither water-birds, nor diggers, but denizens of the air. In Rhamphorhynchus Gemmingi, besides the usual breast-bone, there is a plate with breast-ribs uniting the sternum with the dorsal ribs; they are cartilaginous, or horny, as in birds.

The scapula and coracoid

present the closest resemblance with those of a bird, and only deviate in the coracoid not being inserted in the breast-bone in the manner of birds[M]. It at first seemed that Rhamphorhynchus differed from Pterodactyle in having the scapula and coracoid anchylosed. In R. Gemmingi the bones are either separated or only slightly united.

[M]See however Pl. 1 and 2 of this memoir.

Oken and Goldfuss thought that the scapula consists of an upper and under part, as in lizards. Von Meyer sees nothing of the kind.

The humerus

presents no striking similarity with birds, and differs from bats.

The carpus

is more reptile-like. It consists of two rows of small bones. In birds there is one row made up of two bones.

The pteroid bone.

Von Meyer regards it as having supported the wing-membrane in flight. There has been a good deal of difference of opinionabout it, some thinking it, with Quenstedt, an ossified tendon; others, like Wagner and Burmeister, regarding it as an essential part of the Pterodactyle skeleton. Von Meyer regards its extent as indicating the extent of the wing-membrane. See p. 42.

Metacarpus.

In length the metacarpus resembles that of the Ruminants, in which however it consists of but one bone; while in Pterodactyles there is a separate bone for each of the four fingers; they are closely united together without being blended. In some Pterodactyles the metacarpals of the short fingers are as fine as hairs, so that it is impossible that they should have articular facets on the carpus. In Ornithopterus the metacarpus has some resemblance with that of the bird, but the articulation with the phalanges of the finger for flight is stiff. In Pterodactylus and Rhamphorhynchus there is a free articulation.

Burmeister remarks that the chief articulation of the wing in bats is with the carpus, while in Pterodactyle the articulation is with the end of the metacarpus.

The hand.

Von Meyer finds four fingers. It was formerly supposed that the order of the phalanges was 2, 3, 4, 4, but in the fly-finger this is not the case, Ornithopterus having but two. The number of joints in the other fingers is quite as irregular.

In Pt. longicollum the thumb consists of but one joint.

The Ilium

is more mammalian and avian than reptilian.

Pubis.

The pubis appears to have been excluded from the glenoid cavity, as in Crocodiles. It is more mammal-like than bird-like, and is to be compared with the marsupial bones.

The femur.

In certain Pterodactyles the proximal condyle of the femur resembles birds; but in other Pterodactyles the bone is more mammal-like in its straightness, and development of the upper condyle, and in the presence of a trochanter.

The tibia and fibula

may be compared, from their great length, with birds and flying vertebrate animals.

The fibula is style-shaped, like that of a bird, the lower part being wanting; while in bats the upper part is wanting.

The tarsus,

of two rows, is best compared with that of reptiles. The number of constituent bones has not been definitely determined.

The metatarsus

shows a certain return from the bird type to that of reptiles.

Foot.

Von Meyer never finds more than four toes, and sometimes a stump of a fifth. As a whole, the foot is Saurian-like. It differs from lizards in the number of toes, and approximates to Crocodiles. In Pterodactylus longirostris the formula of the toes is 2, 3, 4, 5, with a stump of two joints;—like lizards, if we abstract the outer toe; and like birds with four toes; but they are liable to variations.

In Pterodactylus scolopaciceps and P. Kochi the formula is 2, 3, 3, 4 joints. In Winkler's specimen of P. Kochi there is also a stump of three joints.

In Pterodactylus micronyx the formula is 2, 3, 3, 3, and a stump of two joints. In P. longicollum the number appears to be different from all the foregoing.

The stump was attached to the side of the outer toe. Wagner, in P. Kochi, supposed it to be on the inner side, and so gave a reverse arrangement to the toes. The stump may be compared with that of some Chelonians, in which it is not furnished with a claw.

There is a difference from birds in the claws being much less developed. It has a true reptile foot. In bats the toes are of equal length. Von Meyer thinks the hind-legs did not enable it to walk on the land.

In some Pterodactyles the flying-membrane is faintly seen. The presence of feathers might be inferred from there being butone finger for flighty as in birds; but the function of feathers is subserved by the long and stiff finger. If it had been covered with scales, as was supposed by Cuvier, some traces of them would be found. The skin was probably naked, and had no connection with the hind-legs as it has in bats; in this respect resembling birds.

The condition of the several parts of the skeleton completely proves that the Pterodactyle was a reptile. Its head, neck, shoulder, and back, resemble a bird; while there are, on the other hand, some striking resemblances with the reptile in the pelvis, tail, and articular parts of the limbs. Sometimes the characters of the two classes run side by side, as in the skull, the fore-limbs, and especially in the hind-limbs, where the shin of a Bird is connected with the foot of a Saurian. The parts in which it corresponds with birds show that Pterodactyles also were flying animals. That we should be entitled to conclude, from the hollow state of the bones, that they belonged to flying animals, is sufficiently proved by Blumenbach, Buckland, Mantell, Owen having mistaken them for bones of birds.

The most absolute proof that it was a flying animal is the pneumatic character of its bones. This condition was discerned by me in some Pterodactyle bones from the Lias of Franken (Jahrb. für Mineral, 1837, p. 316), and was afterwards established by Owen in the Pterodactyles from the Chalk of England. This structure was previously only known in birds. And the supposition readily follows that in the respiratory process there was some similarity between the Pterodactyle and the Birds. They have the proportions of upper-arm and fore-arm which characterize birds of great flight, the humerus short and the fore-arm long; hence it may be presumed that Pterodactyles could fly well. From the absence and presence of the bony sclerotic ring in the eye, it may be supposed that the Pterodactyles were active in the day-time, while Rhamphorhynchus was nocturnal.

After this statement von Meyer gives a discursive summary, in which his views of the classification of reptiles in general and of Pterodactyles in particular are epitomized. And then goes on to combat the views of people who have departed from his classification and attempted to set up classifications of their own; and cites a number of authors who, labouring at the vertebrata,have endeavoured to find a resting-place in their systems for the Pterodactyle. But the chief thing we learn of von Meyer's own views is, that in 1830 he published a classification of extinct Saurians, dividing them into those with limbs like the larger and heavier land-mammals, those with fin-like limbs, and those with a flying-finger. Which divisions have been widely adopted, though authors have sometimes given them other names than those by which they were first made known.

Von Meyer has freely stated the facts about the Pterodactyle, and draws the conclusion that the animal was a reptile; but how such a conclusion was obtained from such facts is a matter on which his pages are silent. One seems to hear the chirrup of the bird in almost every paragraph. The head is in the main a bird's head; the pectoral girdle and the sternal ribs are those of a bird; and very few are the structures in which some reminder of the bird is not present; and in their bones he discovered the pneumatic characteristic and inferred, for the animals bird-like lungs. How, then, comes it that the Pterodactyle is a reptile? We can only suppose the answer to be, Because if the head and pectoral girdle and other bones had been reptilian it would have been a bird.

* * * * *

In the views here epitomized it is difficult always to make out the logical foundations of the conclusions arrived at. Sometimes they have no foundations, and sometimes they represent the different aspects in which a truth presents itself to minds differently constituted or differently conversant with the structures of living animals. In now stating my own views I shall avail myself of the example of some previous writers, and attempt to investigate the Pterodactyle as though they had not written. And then, having placed before him all the theories that are known, the reader will be able to choose the theory that pleases him best, if indeed he needs one.

Much of the discrepancy of opinion that exists is probably due to the use of the inductive method of thought for the discovery of fundamental principles in classification. In palæontology, where the types are more generalized than are living forms, it must always be difficult to reason from the known to the unknown. The known is always more or less incomparable with the unknown; and there can be no reason for inferring that the specialities ofstructure which now accompany specialities in organization would justify us in inferring for the animal, in which the structures formerly were united, the combined organizations of the living animals in which they are now found. On any hypothesis of evolution it would be allowed that the special modifications of a group were attained subsequently to the common plan of the larger group to which it belongs, and are entirely to be attributed to the function which the necessities or organization of the animal caused its structures to subserve. Inductive thought may sometimes discover function from structure, but never makes more than an approximate guess when it endeavours to determine fundamental organization from osseous structures which are not fundamental. And before a naturalist can say, since an animal has for instance a tail like a mammal that in so far it must be affiliated to the mammalia, he must have determined why the mammalian tail has its peculiar characters, and whether it is compatible with any other common plan of organization. And perhaps it might with equal reason be considered reptilian.

Therefore I prefer at firsts instead of reasoning from the details of structure, to adopt theà priorimethod, and ask, not what the Pterodactyle is like in its several bones, but what common plan it had whereon its hard structures were necessarily moulded. For I imagine, if it can be determined what the nervous and respiratory and circulatory structures of the Pterodactyle were, it becomes a secondary matter to know whether the phalanges are like a lizard's, or the pelvis like that of a mammal. If the animal is asserted to be a mammal, a reptile, or a bird, we ought to be able to adduce evidence that it had the soft parts which are deemed distinctive of the selected class. This no one has done or attempted to do.

Hereafter it will be necessary to describe the Pterodactyle's brain.

There is no organ more distinctive between hot-blooded animals on the one hand, and cold-blooded animals on the other, than the brain. In the cold-blooded groups, or those in which respiration is feeble and circulation imperfect, that is to say, in existing fishes, amphibians, and reptiles, the parts of the brain are arranged one behind another, so that when looked upon from above, a portion called the optic lobes intervenes between the anterior masses called the cerebrum and the posterior mass calledthe cerebellum. In the hot-blooded groups, or those with an enormous extent of lung-surface for oxidation of the blood and a four-celled heart for its rapid circulation, that is to say, in birds and mammals, the front part of the brain called the cerebrum is immensely developed in proportion to the other parts, and abuts against the cerebellum and more or less completely covers the optic lobes, which in birds are squeezed out to the sides. The Pterodactyle brain is of this latter kind. And it being taken as a postulate that this kind of brain is the product of the organization which produces hot blood, it follows that the Pterodactyle was a hot-blooded animal.

Again, the Pterodactyle has perforations for pneumatic cells in many of the bones.

There is no structure in the animal kingdom more distinctive of a Class of animals than air-cells perforating the limb-bones. They are connected with a peculiar kind of lung and heart—those of the bird; for in this Class the bronchial tubes open on the outer surface of the lungs into air-cells, which are prolonged through the body into the bones. They follow the blood-vessels, and are most developed in the part of the body most used. In some lizards, as the Chameleon, the sack-like lung at its distal termination is as simple as the air-cells of a bird; but those air-cells are not comparable with the bird's air-cells, since they are not prolongations of the bronchial tubes through the walls of the lungs. And it cannot be inferred that a reptile with wings would develop air-cells like those of a bird: in the first place, because those mammals which have wings do not develop air-cells; and, in the second place, because there is nothing in existing nature to lead any one to think that reptiles might have wings. The mammalian lung is better comparable to that of a bird than is the Chameleon lung, and therefore the air-cell structure might with better reason have been anticipated to occur in the Chiroptera than in a Lizard-ally, if it were dependent on the development of wings. Moreover, among Struthious birds the legs have more of the air-cell prolongations than the wings. Therefore, being a peculiar Avian structure which only exists in association with the Avian heart and lung, it follows that because the Pterodactyle had the pneumatic foramina it also had the structures of which they are the evidence, viz. lung and heart formed on the bird plan.

Thus Pterodactyles have a nervous system of the bird type. That kind of brain only exists in association with a four-celled heart and hot blood.

They have a respiratory organization which is only met with among birds.

With that respiratory apparatus is always associated a four-celled heart and hot blood, which it would necessarily produce.

And with that respiratory organization is always associated a brain of the type that the Pterodactyle is found to possess.

Therefore it is firmly indicated that the general plan of the most vital and important of the soft structures was similar to that of living birds.

This proposition will be incidentally proved in the following memoir, in which it will be seen that with such a common plan, is associated a diversity of details sufficient to demonstrate that these animals are not birds, but constitute a new group of vertebrata of equal value with the birds—the sub-class, Ornithosauria.

ILLUSTRATIVE OF THE MODIFICATIONS OF THE

ORNITHOSAURIA (OR PTERODACTYLES) IN THECAMBRIDGE UPPER GREENSAND.

Case.Comp.Tablet.Ja1

Pectoral Girdle.STERNUM.Pl. 1, fig. 1.

The Sternum is the key to the bony apparatus supporting the anterior limbs. In the Pterodactyles from the Cambridge Greensand it has been well figured and described by Professor Owen, who enunciated its resemblance to the sternum of birds. The sternum in Pterodactyles from the Lithographic Slate, shows its proportional size to the body. The examples found in the Cambridge Greensand have as yet shown no evidence of a composite character like that attributed to Rhamphorhynchus Gemmingi.

The sternum consists of an expanded symmetrical shield having its lateral halves, which are inclined to each other at a large angle (about 150°), contracted superiorly, behind and immediately below the synovial cavities for the coracoids. The vertical angular ridge in which the lateral portions of the sternum unite becomes elevated as it is followed anteriorly, into a strong keel. This keel or interpectoral process is highest in front of the articulations for the coracoids; but the degree of elevation varies with the species. It is prolonged upward and in front of the coracoids for some distance, becoming very massive, and the prolonged mass which is flattened from side to side, reacheslaterally to the outer margins of the coracoid articulations, and on the visceral side a little between and over them. The anterior crest of the keel shows the attachment of powerful muscles.

Professor Owen has observed that only in birds are distinct synovial cavities provided for the coracoids, and that no reptile has a sternum showing characters like those seen in the Pterodactyle. These coracoid cavities are placed as in birds, close together, behind themanubrium, which forms the hindermost part of the keel. They are convex transversely, concave from front to back as in birds, and look upward at an angle of 35°, their main direction being outward and a little backward. Professor Owen recognises the function of the shield-shaped sternum in relation to the mechanism of respiration on the one hand, and on the other hand, for the attachment of pectoral muscles of great bulk and strength.

As is well known, the muscles of the breast in most birds consist chiefly of the 1st, 2nd, and 3rd pectoral muscles, and the coraco-brachialis.

The peculiar form of the bird's sternum appears to be due to the vertical development of the second pectoral muscle, since when the 1st and 3rd muscles are dissected off, the appearance presented nearly resembles that of the sternum in Pterodactyles. There can however be no doubt but that the third pectoral muscle, which in most birds is but feebly developed, attained a far greater bulk in the Pterodactyle, because there is evidence of its powerful insertion in the distal anterior face of the coracoid, as well as of the great lateral extension of the sternal shield to which such a muscle must—by the analogy of birds—have been attached. The peculiar lateral emargination of the sternum appears to be due to the anterior sternal termination of this muscle, caused by the outward direction of the coracoid bone.

Since the coracoids were developed outward and backward so much more than in birds, it would happen, from the apparent different direction of the second pectoral muscle, that the first pectoral muscle which in birds skirts the furculum, must have passed over the coracoid, probably pulling on its inside in opposition to the third pectoral. Either a subdivision of this muscle or a distinct muscle in the same place, in function corresponding to the subclavius muscle, appears to have been powerfully attached fromthe anterior prolongation of the keel of the sternum to the front face of the coracoid. It is improbable that the second pectoral muscle was undeveloped, but merely directed differently to what it is in birds, since, as will be seen, there is a process at the proximal end of the coracoid homologous with that which forms the pulley round which this muscle in birds works.

Professor Owen concludes his remarks by observing that the Pterosaurian breast-bone is in the main formed on the ornithic type. The muscles also appear to be similar to those of birds.

All the specimens are much mutilated, but all show the distinctive post-coracoid lateral emarginations, but as these are not seen in German Pterodactyles they are to be regarded as characters of a peculiar sub-order and not as characteristics of the sub-class.

The example figured in this memoir and by Professor Owen is 25/8inches in antero-posterior measurement, probably about one third its entire length.

A small example in the collection of Mr Reed of York extends 11/4inch in the same measurement, and by the analogy ofP. suevicuswas more than twice that length when perfect. It is remarkable in that the coracoid facets look much less outward and much more backward than in the larger species.

The mammalian sternum is usually in many consecutive pieces like the vertebral column. The types in which it attains any size as an expanded shield are Cetaceans and the Manatee, but in these groups it has no keel and is not connected with the other bones of the pectoral girdle. The proximal portion of the sternum of the Mole is elongated and bird-like, with the shield narrower than in the typical gallinaceous birds, and with the keel similarly developed. It is connected with the humerus by small sub-quadrate bones named clavicles placed at the sides of the proximal end. The sternum in Bats usually consists of a proximal and a distal part. It is narrow except at the proximal-termination where it widens like the letter T or Y; and to the sides of the lateral prolongations are attached the long, slender, curved bones named clavicles, and a pair of ribs. This sternum develops a bird-like keel. Both Mole and Bat are regarded as differing from Pterodactyles in the bone giving attachment to the clavicles instead of to the coracoids. The proximal part of the sternum in both the living animals, gives attachment to but one pair of sternalribs. The Pterodactyle sternum otherwise differs from the Bats in having the articulations for the coracoids close together, of a peculiar concavo-convex character, with a massive portion or keel prolonged forward in front of the coracoid articulations. The Bat cannot be said to resemble the Pterodactyle closely. The sternum of the Mole differs from that of the Pterodactyle in having a less developed shield, and in having a more developed keel which is not prolonged in front of the coracoid articulations. These examples demonstrate that resemblance in conformation is functional, and no proof of affinity.

Pterodactyles make some approach in the proportions of their sternum to Struthious birds. But the Struthionidæ have the bone thick, do not develop a keel, nor, have they an inter-coracoid process while the coracoid articulations are singularly long and narrow instead of being ovate. With other birds the Pterodactyle sternum agrees in giving attachment to the coracoid bones by synovial articulations, in the bone being shield-shaped, and supporting a more or less developed keel. The keel is chiefly developed at the proximal end, as in the Albatross, which has the bone broad; and it is prolonged in front of the coracoids exactly as inMergus merganser, which sternum if a little broader in the shield and thicker in the keel would very nearly reproduce the sternum of the Pterodactyle, even to the "post-coracoid lateral emargination" of Cambridge specimens. Among reptiles the only form which suggests comparison is the Chameleon, in which however the sternum consists of an anterior and a posterior part as in the Bats, the back part narrow, and the front part a long lozenge shape, with a keel made by inclination of the sides of the bone to each other as in the Dodo, but the keel such as it is, is at the back part of the bone, and there is no prolongation in front of the coracoids as in Pterodactyle. The coracoids are broad, and are applied to the two anterior sides of the lozenge. The Crocodile has a narrow flat sternum which is prolonged anteriorly between the coracoids.

The resemblance is greater with mammals than with reptiles. From birds the Pterodactyle sternum makes no essential difference, and in the Merganser finds a close ally.

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