The Ornithosauria / An elementary study of the bones of Pterodactyles made from fossil remains found in the Cambridge Upper Greensand, and arranged in the Woodwardian Museum of the University of Cambridge

Transcriber Note

All corrections listed in the "[Errata]" have been made in the text. Linking text for the plates has been added to the "Contents".

THE ORNITHOSAURIA:

AN ELEMENTARY STUDY

OF

THE BONES OF PTERODACTYLES.

PRINTED BY G. J. CLAY, M.A.
AT THE UNIVERSITY PRESS.

THE ORNITHOSAURIA:

AN ELEMENTARY STUDY

OF

THE BONES OF PTERODACTYLES.

MADE FROM FOSSIL REMAINS FOUND IN THE
CAMBRIDGE UPPER GREENSAND,

AND

ARRANGED IN THE WOODWARDIAN MUSEUM OF THE
UNIVERSITY OF CAMBRIDGE

BY

HARRY GOVIER SEELEY,

OF ST. JOHN'S COLLEGE, CAMBRIDGE.

WITH TWELVE PLATES.

"And when the appointed end comes, they lie not dishonoured in
forgetfulness,"—Xenoph. Memor. Book 2, c. 1, § 83.

DEIGHTON, BELL, AND CO.
LONDON: BELL AND DALDY.
1870.

[All Rights reserved.]

The expense of printing this volume has been defrayed out of the Funds of the Syndics of the University Press; and Professor Sedgwick hereby expresses his grateful thanks to them for this great favour.

PREFACE.

This memoir is a portion of the Catalogue of the Woodwardian Museum which has been made at Professor Sedgwick's request and at his cost. When the Professor laid upon me his commands to prepare a Catalogue of the Museum, it was planned in three distinct works. First, a series of indexes to the specimens in the great divisions into which the Museum is arranged; secondly, a series of memoirs upon the orders and classes of animals concerning which new knowledge is given by fossils in the Museum; and, thirdly, memoirs descriptive of those species contained in the arranged collections which are at present unknown in scientific writings.

For the convenience of students the Catalogue is made in parts. The Syndics of the University Press printed last autumn as an example of the "Indexes to the Museum," an Index to the Pterodactyles, Birds, and Reptiles from the Secondary Strata. And this memoir is an example of the second kind of Catalogue, which explains the structures of the Pterodactyles of the Cambridge Greensand. In its progress questions have arisen which necessitated an examination both of the method, of research in comparative anatomy and of its results in classification. And in so far as the views here advanced differ from those commonly taught, the discrepancy is due to the writer's imperfect faith in the results of the inductive method of research, as commonly used by modern writers on Palæontology. It has not been consistent with the plan of this little work to do more than scatter through it a few hints upon method, a subject which will more fitly be discussed with a part of the Catalogue which forms a synopsis of the osteology of the fossil animals usually named Reptiles. The views here urged have however but little of novelty. The name Ornithosauria was proposed by the distinguished naturalist Prince Charles Bonaparte in 1838. The group as an order was recognized by Von Meyer in 1830. The affinities of the brain appear to have been detected by Oken, and the bird-like character of the respiratory system was expounded by Von Meyer. And most of whatever this memoir contains has been already thought or discovered by the German philosophers, who have had the Pterodactyles as fossils of their fatherland, though my own conclusions were arrived at separately and from different materials.

The oldest Ornithosaurians are from the Muschelkalk of Germany. In England the oldest are from the Lias,—several species of Dimorphodon—a genus in some respects nearly resembling the Pterosaurians of the Cambridge Upper Greensand. In the Oolite of Stonesfield are several species of Rhamphorhynchus or a similar genus. The great Pælolithic period from the Oxford Clay to the Kimeridge Clay, has yielded in its several divisions small Pterodactyles of new species. And the Psammolithic period from the Portland Sand to the Lower Greensand has afforded many excellent remains both of true Pterosaurians in the Purbeck, Wealden, and Potton Sands, and of animals which indicate a new order of Ornithosauria having affinities with Von Meyer's thick footed saurians, the Dinosauria. In the Cretaceous series, Galt, Upper Greensand, and Chalk all have representatives of the Pterosauria; but no English stratum has hitherto yielded so many as the Cambridge Upper Greensand. From this formation the collection accumulated during Prof. Sedgwick's long professoriate is unequalled; though, excepting a few fine bones from the Chalk and the Purbeck Limestone, the Woodwardian Museum is as yet deficient in Ornithosaurians from the other Secondary Rocks. Until descriptions of these animals shall have been published a classification of the Ornithosauria must necessarily be provisional. And it cannot be expected that descriptions of the structure of Cretaceous Pterosaurians here given will hold good for all the Ornithosaurian sub-class.

Finally, I have gratefully to express my thanks to the many friends, English and German, who have aided me with specimens and with their writings; to the chiefs and officers of the English museums, especially Prof. Owen, Prof Humphry, Prof Newton, Prof Phillips, Prof Flower, and Prof. Huxley; to the officers of the University Library, especially Mr Bradshaw, and Mr Crotch, for aid in consulting books; but chiefly to Prof Sedgwick, who while employing me as his paid Assistant to aid him in his Museum work, has generously encouraged me to carry on for several years, without restraint and as part of my daily labour, an investigation of which this treatise is the first fruit. Prof. Sedgwick has placed at my disposal an ample number of copies for distribution among those who take an interest in the Museum; and especially among those who have contributed to the Ornithosaurian collections, and aided me in my work.

January 3, 1870.

CONTENTS.

Osteological collection illustrative of modifications of Ornithosauria in the Cambridge Greensand, pp. 28-94.

ERRATA.

PAGE	LINE
[4],	2,		from bottom, for procælian read procœlian.
[7],	13,		for Ossements read Ossemens.
[8],			last line, paragraph (2), for outermost read innermost.
[10],	21,		for Sömmering read Sömmerring.
[11],	5,
[11],	13,
[14],			note, for Beyerischen read Bayerischen.
[15],	5,		for ?zygapophyses read spinous-processes.
[17],	6,		from bottom, for Herman read Hermann.
[37],	5,		from bottom, after "spine as" insert "are"
[92],			line above 'the Dentary Bone,' for Pterodactyle read Pterodactyles.
[97],	11,		for Günter read Günther.
[99],	4,		for Ichthyopteria read Ichthyopterygia.
[101],	11,		from bottom, for procælous read procœlous.
[102],	15,		for procælous read procœlous.
[111],	8,		for Sömmering read Sömmerring.

For epipubic bone read prepubic bone, pp. [61], [102], [109], [110], [111], and [pl. 8].

INTRODUCTION

TO THE

OSTEOLOGY OF THE ORNITHOSAURIA FROM THE CAMBRIDGE UPPER GREENSAND.

[Materials.]

The Cambridge Upper Greensand has yielded to collectors bones which illustrate nearly every part of the skeleton of the animals that are commonly named Pterodactyles. Large collections have been acquired for the Woodwardian Museum. A series of more than 500 bones have been arranged to exemplify the osteology and organization of the Ornithosauria in the area when the Cambridge Greensand was deposited. And this memoir is written to explain briefly some of the structures of the soft and hard parts of those animals which are exhibited or demonstrated by these relics. Another collection of nearly 400 bones has been arranged, which displays in association, as they were found entombed in the old Greensand sea-bed, the remains of the skeletons of thirty-three animals of the Pterodactyle kind. The whole of the remains from this formation hitherto gathered cannot be computed to have pertained to fewer than 150 individuals, which indicate a new sub-class of animals, two new genera and at least twenty-five new species.

The bones were mostly of a paper or card-like thinness, and were originally hollow like the thin bones of birds. In the jaws of other animals, and in the sea, they were easily fractured, so that proximal ends and distal ends and shafts and split bones abound, while perfect bones are almost unknown. Even those bones like the carpals, which almost retain their entirety, invariably show indications of having been rolled on the sea-shore among the nodules of phosphate of lime with which they now occur, in their angular margins being rounded, and in the removal of slender processes. The rock in which these fossils are found is a thin bed of chalky marl which is heavily charged with dark-green grains of Glauconite, and is quarried largely, and entirely dug away to be deprived of the dark-brown nodules of phosphate of lime with which it is stored. In digging and in the subsequent washing, the workmen, stimulated by an ample reward, pick out the fossils as they are discovered. They are separated easily from the matrix of investing marl, so that every aspect of each bone is seen, except for the occasionally adherent oysters and the masses of phosphate of lime, with which material the bones are also filled. Hence these remains afford facilities for the study of the joints such as no other specimens have presented; and from their large size and comparatively great numbers, render easy the labour of the student who seeks to contrast them with the bones of other animals.

The osteological collection has been formed without regard to species or genera, and arranged to exhibit the structure and organization of the tribe of animals. So far as possible each bone, as humerus, femur, &c., has its variations of structures and form contrasted on a single tablet. The series comprises the following bones:

Fore-part of sternum.
Coracoid (perfect).
Scapula (nearly perfect).
Humerus (perfect).
?Radius (proximal end).
Radius (distal end).
?Ulna (proximal end).
Ulna (distal end).
Proximal carpal.
Distal carpal.
Lateral carpal.
Wing-metacarpal (proximal and distal ends).
First phalange (proximal and distal ends).
Second phalange (proximal end).
Metacarpal or metatarsal (distal end).
Claw phalange.
Os innominatum (parts of ilium, ischium, and pubis).
Femur (perfect).
?Tibia (proximal end).
Atlas and axis.
Cervical vertebræ.
Dorsal vertebræ.
Sacrum and sacral vertebræ.
Caudal vertebræ.
Lower jaw (dentary and articular ends).
Premaxillary bones, &c.
Teeth.
Quadrate bone (distal end with quadrato-jugal).
Ethmoid with basi-sphenoid.
Occipital and parietal segments of skulls.
Basi-occipital and basi-temporal.
Cast of brain-cavity.

They are exhibited in Compartments a, b, c of the Table-case of Cabinet J. The letter F in a circle is placed against figured specimens.

History.

The Cambridge Pterodactyles first attain prominence in scientific literature in the year 1859. Professor Owen had figured (plate 32, fig. 6-8) fragments of bones in the Palæontographical Society's Monograph for 1851; the distal end of a large ulna (fig. 6); the shaft of a phalange of the wing-finger, probably the first (fig. 7); and the upper portion of the shaft of a small humerus showing part of the radial crest (fig. 8). Inadvertently the last specimen was referred to the Lower Greensand. But although fragments of humerus of Pterodactyle and vertebræ of Pterodactyloid animals have in the last few years been gathered from the Potton Sands, those deposits were believed to be barren of fossils when Prof. Owen wrote; and all the Pterodactyles yet made known from near Cambridge were collected from the Cambridge Upper Greensand.

Among the earliest successful collectors were Mr James Carter, the Rev. H. G. Day, St John's Coll.; Prof. G. D. Liveing, St John's Coll.; the Rev. T. G. Bonney, St John's Coll.; and Mr Lucas Barrett, Trin. Coll.; and the Rev. Prof. Sedgwick, Trin. Coll., on behalf of the Woodwardian Museum. Mr Day and Mr Bonney both presented every specimen from their cabinets which could enrich the University collection. And in the last ten years the Woodwardian Museum has acquired, through the skillful collecting of the Messrs Farren, the present materials. The associated sets of bones were formed by William and Robert Farren, who, obtaining the specimens from day to day as they were discovered, were enabled to put together such parts of the skeleton as remained together on the sea-bottom. These collections will hereafter be used for the elucidation of species. They are the only materials which can give the proportions of the Cambridge Ornithosaurians, and the contrast of aspect which distinguished the living animals from those from other rocks.

The other collections of these fossils are those of Mr William Reed and Mr J. F. Walker at York, the Museum of Practical Geology, and the British Museum.

The Woodwardian specimens as collected were placed in the hands of Prof. Owen, and were first made known in the Professor's lectures on reptiles and birds delivered at the Museum of Practical Geology in 1858. In that year Prof. Owen communicated to the British Association for the Advancement of Science, and printed in their Report, the matter of the memoir which was published with plates by the Palæontographical Society in 1859. In this latter year Prof. Owen communicated to the Royal Society an account of the vertebral column of Pterodactyles. In 1859 Prof. Owen also produced a classification of recent and fossil reptiles at the meeting of the British Association, in which the order Pterosauria appears with new characters—such as the pneumatic structure of most of the bones—drawn from Cambridge specimens. In 1860 Prof. Owen produced another memoir on Pterodactyles, which was published by the Palæontographical Society. A brief account of the tribe appeared about the same time in the Professor's Palæontology.

In these writings are descriptions of the various parts of the vertebral column. Their procœlian centra are described, and the pneumatic foramina are noticed and supposed to have communicated with air-cells. They are compared with birds, and distinguished from birds; but although the order is classed with reptiles no contrast with reptiles is made. Other bones described are a basi-occipital, and a doubtful bone, then thought to be a frontal, but which is more like the neural region of the sacrum.

The sternum is compared with the sternum of the birds Apteryx and Aptenodytes, is stated to be formed, in the main, on the Ornithic type, and to possess distinct synovial articular cavities for the coracoids such as only occur in birds. The inter-coracoid process of the sternum is compared with that of Bats, Birds, and Crocodiles.

The mechanism of the framework of the wings is said to be much more bird-like than bat-like, the anchylosed scapula and coracoid being remarkably similar to those of a bird of flight. The coracoid is shorter and straighter in birds than in Pterodactyles, but no comparisons are made with reptiles.

The humerus is known only by the proximal end. It is said to conform at its proximal end more with the Crocodilian than with the Avian type, but to have the radial crest much more developed than in either Crocodile or Bird. The bone is, however, chiefly compared with birds, and is figured between corresponding bones of a Vulture and a Crocodile. The pneumatic texture is said to be as well marked as in any bird of flight.

Of the carpus it is said, the Pterodactyle, in the complete separation of the metacarpus from the antibrachium by two successive carpals answering to the two rows, adheres more closely to the reptilian type than to that of birds. But the row which was regarded as proximal is the distal row, while the supposed distal row is proximal.

The claw-phalange and distal end of the wing-metacarpal, the mandible, teeth, and jaw are the other bones described, but their comparative osteology is not discussed. In the Professor's account of a fragment of a jaw it is said, "The evidence of the large and obviously pneumatic vacuities now filled with matrix, and the demonstrable thin layer of compact bone forming their outer wall, permit no reasonable doubt as to the Pterosaurian nature of this fossil. All other parts of the flying reptile being in proportion, it must have appeared with outstretched pinions like the soaring Roc of Arabian romance, but with the demoniacal features of the leathern wings with crooked claws, and of the gaping mouth with threatening teeth, superinduced."

When the specimens on which Prof. Owen had founded the foregoing views of the osteology and classification of these animals were at length returned to the Woodwardian Museum, it became a duty of the present writer to arrange and name them. And in a Memoir on Pterodactyles which was communicated to the Cambridge Philosophical Society and read March 7 and May 2 and 16, 1864, a position was claimed for them, distinct from reptiles, as a separate sub-class of Sauropsida, nearly related to birds.

In September of the same year a communication was made to the British Association "On the Pterodactyle as evidence of a new sub-class of vertebrata (Sauromia)," with enlarged drawings of the skull and some of the other bones, in which the conclusions arrived at were that, excepting the teeth, there is little in such parts of the head as are preserved to distinguish the Cambridge Pterodactyles from birds; and that the remainder of the skeleton gives a general support to the inference from the skull.

Papers were communicated to the Cambridge Philosophical Society on February 17, 1868, on indications of Mammalian affinities in Pterodactyles in the pelvis and femur, and February 22, 1869, on the bird-like characters of the brain and metatarsus in the Pterodactyls from the Cambridge Greensand. The other references to Cambridge specimens are in a paper "On the literature of English Pterodactyles" in the Annals and Magazine of Natural History for Feb. 1865, and in "An epitome of the evidence that Pterodactyles are not reptiles, but a new sub-class of vertebrate animals allied to birds," in the same magazine for May, 1866.

In the meantime Prof. Owen's views have somewhat changed. In the first volume of the Comparative Anatomy and Physiology of the Vertebrata (1866), the Pterosauria are classed as the highest group of reptiles, and take rank above the Dinosauria. In the second volume of that work (1866), occurs the following passage:

"Derivatively the class of birds is most closely connected with the Pterosaurian order of cold-blooded air-breathers. In equivalency it is comparable rather with such a group than with the Reptilia in totality, or with the Mammalia."

Organization.

Nearly every writer on Pterodactyles, who has expressed any opinion at all, has formed an estimate of his own of their organization. They have been assigned to almost all possible positions in the vertebrate province, by great anatomists who all had before them very similar materials. An account of these views is given by von Meyer in his monograph of the Pterodactyles of the Lithographic Slate. It will not be necessary to discuss these conclusions here, for the materials from the Lithographic Slate and those from the Cambridge Greensand are so different that no light would be thrown on the organization of the animals by an exposition of any fallacious inferences from German specimens. In England they are classed with Reptilia, chiefly through the influence of the discourse upon them given by Baron Cuvier in his Ossemens Fossiles[A]. It therefore may conduce to a clear view of the subject to quote in Cuvier's words the passages in that memoir which have been supposed to establish their position among reptiles. He says,—"Ayant encore porté mon attention sur le petit os cylindrique marqué g (i.e. os quadratum) qui va du crâne à l'articulation des mâchoires, je me crus muni de tout ce qui étoit nécessaire pour classer ostéologiquement notre animal parmi les reptiles." The exact relations of the quadrate bone are not seen in either Cuvier's or Goldfuss' or von Meyer's figures of this Pterodactyle, the P. longirostris; but in von Meyer's figures of P. crassirostris, P. longicollum, and P. Kochi it appears to be a free bone articulated to the squamosal and petrosal region of the skull and with the lower jaw. This is not the case with either Chelonians or Crocodiles, which have the quadrate bone firmly packed in the skull; nor is it paralleled even among those lizards and serpents which have the bone as free; while, on the contrary, it is characteristic of the whole class of birds. The form of the bone is not more Lacertian than Avian, while its direct attachment to the bone of the brain-case finds no parallel among lizards, but is exactly paralleled in all birds.

[A] Tome V. Part a, pp. 358, 383. Edition, 1814.

Cuvier then goes on to say, "Ce n'étoit pas non plus un oiseau, quoiqu'il eût été rapporté aux oiseaux palmipèdes par un grand naturaliste[B]." Which position he supports as follows:—

[B] Blumenbach.

(1) "Un oiseau auroit des côtes plus larges, et munies chacune d'une apophyse récurrente[C]; son metatarse n'auroit formé qu'un seul os, et n'auroit pas été composé d'autanut d'os qu'il a de doigts." These, though they may not be characters which are those of birds, are certainly not eminently reptilian. The elongated form of the tarsals in birds is peculiar, but quite functional, as may be seen among the Penguins, where, when the so-called tarso-metatarsal bone is no longer erect, it becomes much shorter, and is nearly separated into three distinct bones. The cretaceous Pterodactyles appear to have this bone exactly like that of birds.

[C] This shown in other specimens since figured, and in the specimen from Stonesfield in the Oxford Museum.

(2) "Son aile n'auroit eu que trois divisions après l'avantbras, et non pas cinq comme celle-ce." This is a difference, but a difference of detail only, and not a reptilian character. The creatures have wings; and no reptile known, from recent or fossil specimens, has wings. The general plan of the wing, though very unlike, approximates to that of a bird. Most birds have two phalanges in the long finger, though some have three. One Pterodactyle is described as having only two phalanges in the wing-finger, while most of the German specimens appear to have four phalanges. In birds the longest finger appears to be the middle one, while in Pterodactyles it is the innermost one.

(3) "Son bassin auroit eu une toute autre étendue et sa queue osseuse un toute autre forme; elle seroit élargie, et non pas grêle et conique." The pelvis of Pterodactyle is not reptilian, and no living reptile has a pelvis like it. It is not unlike the pelvis of a Monotreme, but the ilium is more Avian. It resembles the pelvis of Dicynodon. And the discovery of a long-tailed bird-like the Archæopteryx shows that the tail is like that of old birds, even if it also presents some analogy in form to that of certain reptiles and mammals.

(4) "Il n'y auroit pas eu de dents au bec; les dents des harles ne tiennent qu'à l'enveloppe cornée, et non à la charpente osseuse." This is not a reptilian character. Among reptiles some tribes have teeth, others want them; and among mammals some animals are without teeth, though they are so characteristic of the class. It is an anomaly that birds should all be toothless. And so, without citing the supposed teeth of Archæopteryx, it may be affirmed that it would be no more remarkable for some birds to have teeth than it is for some mammals and reptiles to be without them.

(5) "Les vertèbres du cou auroient été plus nombreuses. Aucun oiseau n'en a moins de neuf; les palmipèdes, en particulier, en ont depuis douze jusqu'à vingt-trois, et l'on n'en voit ici que six ou tout au plus sept." This is a variation of detail such as, had it occurred among birds, would hardly have been deemed evidence of their affinities. When the variation of the neck-vertebræ ranges from 23 to 9, the further reduction of the number to 7 becomes insignificant, and does not show that the animal was a reptile.

(6) "Au contraire, les vertèbres du dos l'auroient été beau-coup moins. Il semble qu'il y en ait plus de vingt, et les oiseaux en ont de sept à dix, ou tout au plus onze." This modification is obviously the result of smaller development of the pelvic bones from front to back, and hence of the small number of vertebræ in the sacrum. It does not support the reference of Pterodactyles to the class of reptiles.

Speaking of the teeth, it is said, "Elles sont toutes simples, coniques, et à peu près semblables entre elles comme dans les crocodiles, les monitors, et d'autres lézards." The teeth of Pterodactyles are (in the skull) for the most part in the premaxillary bones, in which it is so characteristic for the teeth of animals to, be merely conical and simple. Therefore it would have been difficult to imagine the teeth to have been anything but what they are, whatever the affinities of the Pterodactyle might be.

It is remarked, "La longueur du cou est proportionée à celle de la téte. On y voit cinq vertèbres grandes et prismatiques comme celles des oiseaux à long cou, et une plus petite se montre à chaque extrémité." This adds nothing to the evidence for its reptilian character.

"Ce qui est le plus fait pour étonner, c'est que cette longue téte et ce long cou soient portés sur un si petit corps; les oiseaux seuls offrent de semblable proportions, et sans doute c'est, avec la longueur du grand doigt, ce qui avoit determiné quelques naturalistes à rapporter notre animal à cette classe." Nor is this evidence that the animal was a reptile. And in many minor matters Cuvier is careful to show how their modifications resemble those of birds; and when this is not so, birds are the only animals from which he finds them varying. And the few suggestions which are thrown out respecting their affinities with lizards are upon points which are also common to birds.

Thus what Cuvier did was to distinguish these animals from birds, and incidentally to show that their organization was a modification of that of the Avian class. And the legitimate inference would have been that their systematic place was near the birds, and not that they were reptiles.

But in Germany Cuvier's views on Pterodactyles have by no means been submissively received; and great anatomists, since he wrote, have propounded and defended views as various as those of the anatomists who preceded him, and with no less confidence in the results of their science. In the brief space at my command it would be impossible to do justice to the works of this array of philosophers, and therefore I present in a somewhat condensed version the epitome of their conclusions given by Hermann von Meyer in his Reptilien aus dem Lithographischen Schiefer der Jura. They form a commentary on the casts of Solenhofen Pterodactyles contained in the Woodwardian Museum.

Sömmerring

regarded the Pterodactyle as an unknown kind of bat, and thought that Cuvier was misled by Collini's imperfect description. He believed that he found in them different kinds of teeth as in mammals; and regarded them as differing from bats chiefly in having larger eye-holes, a longer neck, four fingers and four toes, a longer metatarsus, and in having but one elongated finger; and found the closest analogue of the fingers in Pteropus marginatus of Bengal. And although inclined to place the Pterodactyle between Pteropus and Galeopithecus, he suspects from the bird-like characters of the head and feet that its true place is intermediate between mammals and birds.

Oken[D].

[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 be found; 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 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."

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 those of 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 opinion about 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 but one 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 of structure 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 the à priori method, 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 called the 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.

[OSTEOLOGICAL COLLECTION]

ILLUSTRATIVE OF THE MODIFICATIONS OF THE

ORNITHOSAURIA (OR PTERODACTYLES) IN THE
CAMBRIDGE UPPER GREENSAND.

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, reaches laterally 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 the manubrium, 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 from the 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 2⁵/₈ inches in antero-posterior measurement, probably about one third its entire length.

A small example in the collection of Mr Reed of York extends 1¹/₄ inch in the same measurement, and by the analogy of P. suevicus was 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 sternal ribs. 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 in Mergus 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.

CORACOID.
[Pl. 2, fig. 1-6.]

Commonly the coracoid in the Cambridge Pterodactyles is anchylosed to the scapula: occasionally the bones are separate, though the separation has hitherto only been observed in the largest species. In 1851 Professor Owen, when figuring the anchylosed ends of the scapula and coracoid in Pterodactylus giganteus (Bowerbank), observed that in no part of the skeleton does the Pterodactyle more nearly resemble a bird than in the scapular arch; a view again urged emphatically in 1859 when similar fragments were described from the Cambridge Greensand. Since then perfect examples of the coracoid have occurred, which show the characters given in the following description.

The bone is long, with sub-parallel sides, sub-triangnlar in section, with the proximal end expanded exteriorly and posteriorly, resembling in form the coracoid of a bird. The front surface looks forward and outward; it is flattened, is a little convex transversely, and a little convex in length; it is rugose with muscular attachments, which terminate in a tubercle on the uppermost fourth of the front, usually near to the inner side. The middle third of the slightly concave inside margin of the front aspect, is sharply angular; the parts above and below it have the angularity rounded off. The outside margin, a little more concave than the inside margin, is sharply angular in its distal third, in which the front gradually widens to near the sternal articulation, when it contracts—the whole sternal termination of the bone being directed a little inward towards the manubrium of the sternum. The inside, which faces the opposite coracoid, is convex transversely in the lower half or two-thirds; its distal termination is carried inward. The expanded proximal end of the inside is flattened, or channelled, by the developement inwardly, at the proximal end of the ridge formed with the front side, of a long strong process homologous with that on the inner side of the coracoid in birds. The channel so formed rounds on to the proximal surface of the bone, and extends backward to the limit of the scapula; over it the second pectoral muscle may be presumed to have worked[N]. The third side of the bone is much more concave in length than either of the others; it looks backward, outward, and downward, the proximal end being turned outward and downward more than the distal end; it is a little concave transversely at the expanded proximal end. Near the distal end there are sometimes visible a few faint marks of the insertion of muscular fibres, but they are much less distinct than those made by the coraco-brachialis muscle in the corresponding region of the coracoid in birds. Throughout its length it rounds into the inner side, and the upper third rounds convexly into the front. On the most posterior part of this aspect of the proximal end is a groove terminating in a long pneumatic foramen, partly in the coracoid, partly in the scapula.

[N] The homologous process is more developed in Pterodactylus giganteus. See f. 7. pl. XXXI. Owen, Cret. Rept.

The muscular attachments on the front aspect of the coracoid appear to be two; one large and long inserted into the inner half of the middle third of the bone, terminating at the proximal end in a tubercle. No specimen shows the distal end of the insertion. This may indicate a subdivision of the first pectoral muscle. The other insertion, if it be distinct, is long and much narrower and at the distal end of the bone. This, according to the analogy of birds, should be the third pectoral muscle; if the insertion should be but part of that to which it is distally adjacent, then the third pectoral muscle must have had an enormous developement unparalleled in birds.

The distal end of the bone terminates in a synovial articulation concave transversely, convex from front to back, in form transversely ovate: the narrow side of the articulation, like the thin edge of the coracoid, being exterior. The articulation is about three fourths of the transverse diameter of the distal end; it is at right angles with the long axis of the bone, and looks downward and a little backward.

The proximal end, massively enlarged outward and backward, presents on the proximal surface three well defined regions. The largest of these is an irregular flattened surface half ovate in form, inclined to the axis of the bone at about 45°, looking backward, and upward also, when the bone is held vertically; the mesial hindermost half of the radius of this area is occupied by a pneumatic cavity: to this surface is applied the scapula. The next largest surface is rectangular and oblong, looking upward, outward, and a little forward. The transverse aspect which looks outward being nearly half as long again as the antero-posterior aspect which looks forward; in the latter direction the area is slightly concave, in the former direction it is slightly convex; its posterior boundary is parallel with the front of the bone: this area forms the anterior moiety of the glenoid cavity, to which the proximal end of the humerus is applied.

The remaining surface of the proximal end is sub-quadrate, adjoins the two other surfaces as well as the front and the inside of the shaft, it is conically concave.

The entire bone when applied to the sternum looked outward, backward and upward.

Professor Owen remarked (1859) that the "coracoid is shorter and straighter in birds than in Pterodactyles, but is commonly broader, and with a longer and stronger anterior process."

The points in which the Pterodactyle coracoid resembles that of birds (e. g. Gallinaceæ) are the long slender triangular shaft; the concavo-convex articulation to the sternum; the convexity of the distal end in front, and its concavity behind; the posterior aspect of its scapular surface, and the pneumatic foramen.

The points in which it is distinct from birds are that the bone is not produced proximally beyond the glenoid cavity for the humerus, which, instead of being lateral as in birds, and looking outward, in Pterodactyles forms the proximal-termination of the bone. The sternal articulation is proportionally much shorter transversely in Pterodactyles, terminating in a convex margin which rounds up into the thin outer margin, as in the immature coracoid of the common Cock. It is bow-shaped in front instead of being straight, and is commonly longer than in birds. The usual ossified connection with the scapula is not entirely unparalleled in birds, the whole pectoral girdle being sometimes anchylosed into a bony mass as in the frigate bird.

In the monotremata, the only mammals in which the coracoids are separate bones, they rather recall those of Ichthyosaurus than those of any other animals, and have no connection with the sternum. The bone which represents it functionally in placental mammals is the clavicle.

In no reptile is there any structure resembling the Ornithosaurian coracoid. The nearest approximation is made by the Crocodile, in which as in the Chameleon the pectoral girdle is formed as in pterodactyles and struthious birds by scapula, coracoid and sternum. But in the Crocodile the coracoid is compressed, and expanded from side to side both proximally and distally. Distally it has no synovial articulation with the sternum; and proximally a wide process of the bone extends beyond the articulation for the humerus as in birds, only the scapula unites with the prolonged part, and the glenoid cavity looks forward and inward.

The coracoid is essentially avian in its affinities, though with peculiar characters of its own. In the German genera it closely resembles specimens from the Cambridge Greensand.

23 specimens are exhibited. Nos. 4, 10, 12, are the middle parts of shafts of left coracoids. Nos. 3-12, 22, are the middle parts of shafts of right coracoids. Nos. 2, 5, 14, are proximal ends of left coracoids. Nos. 1, 6, 8, 9, 23, are proximal ends of right coracoids. Nos. 15, 16, 17, 18, 19, 20, 21, are distal ends of left coracoids. No. 13 is a nearly perfect left coracoid, and No. 7 is the glenoid cavity for the humerus formed by a right coracoid with the anchylosed scapula.

SCAPULA.
[Pl. 1, figs. 2-12.]

Professor Owen described the scapula of Pterodactylus giganteus in 1851, and added further particulars regarding the Species from the Cambridge Greensand, in 1859; but, as with the coracoid, only the humeral end has hitherto been figured. The only example sufficiently perfect to give the length and proportions of the bone is preserved in the collection of Mr Reed, of York. This left scapula is a stout strong bone, short in proportion to its strength, of flattened ovate form in section, expanding at the humeral end into an irregular sub-rhomboid mass. It is smaller in the middle, contracting both from side to side and from back to front till the back to front measurement is ⁷/₁₆ of an inch, and the side to side measurement is ¹¹/₁₆ of an inch, and it expands a little at the free end, which terminates in a smooth heart-shaped surface, convex in the long diameter, which measures ⁷/₈ of an inch, and flat in the short one, which measures nearly ⁵/₈ of an inch; it is at right angles with the inside of the bone. The sharp superior lateral outline is concave, but less so than the inferior lateral outline; into that inferior aspect of the bone the sides are more fully rounded. The flattened inner surface applied to the ribs is concave in the length of the bone, which measures 3¹/₂ inches; the posterior half of which is convex transversely, the anterior humeral half is concave transversely so as to be cup-shaped, and measures in extreme width 1¹¹/₁₆ inch; the outline of the transversely convex outer side in length is nearly straight, but the exterior part and glenoid cavity of the proximal end is broken away, and there only remains a small median proximal surface broken at both ends, a little concave in length, measuring ⁵/₈ of an inch, and convex in breadth measuring ¹/₄ of an inch.

As there is no specimen in the Woodwardian Museum showing clearly the connection of the proximal with the distal end, the specimens are arranged on separate tablets.

Humeral End of Scapula.

The humeral end of the scapula exhibits in the different species much diversity of form, spreading laterally from the shaft, and terminating in an elongated articular surface truncating the bone nearly at right angles. On its inferior border it throws out a large convex tuberosity, separated from the humeral articular surface by a deep emargination. From the tuberosity usually arises a crescentic row of muscular insertions, which is continued inward and forward over the most compressed part of the scapula towards the middle of the humeral articulation. From the superior margin, interior to the coracoid, arises a prominent ridge, the spine of the scapula, which is directed diagonally backward and downward, terminating in the middle of the outer surface, where it is bordered on the anterior aspect by a long narrow muscular attachment. Between this spine and the elevated margin of the glenoid cavity the bone is much compressed and concave.

On the inside surface of the bone there appear to be small muscular attachments in front of and behind the great tuberosity. The area between the spine and the inner surface is sometimes flattened, sometimes gently convex.

With well-marked distinctive characters in the inferior tuberosity, the pre-tuberous emargination and the thick rounded form of the bone, the Pterodactyle scapula is intermediate in character between that of a mole, a bird, and the crocodile; wanting the sabre shape of the bird's scapula, it also wants the wide expanded form of the scapula of the Crocodile, but resembles the latter in the direction and degree of developement of the spine. This modification is probably due to the outward direction and clavicular function of the coracoid, as well as to the raptorial habit of the organism.

In no living Reptile is there a scapula to be compared with that of the Pterodactyle, for besides the free end being expanded, in the crocodile, it is also thin and squamous and the bone makes a continuous curve with the coracoid as in struthious birds, and not a sharp angle as in Pterodactyles. The "spine" in crocodiles is on the anterior border of the bone and directed upward and backward, while in Pterodactyles it is on the posterior border and directed upward and forward. In the Chameleon the scapula is more elongated and narrow, narrower in proportion to its length than in Pterodactyle, but becomes rapidly wide at its union with the coracoid. It is curved in length so as to fit on to convex ribs. A scapula presenting some resemblance to Pterodactyle is found in certain Liassic Ichthyosaurs.

Among mammals a straight elongated narrow scapula is rare. The mole however has a scapula of this kind somewhat cylindrical in its proximal half and not much expanded at the free end, on which there is a small spine. The anterior emargination above the glenoid cavity in Pterodactyle is entirely mammalian, as is the anterior tuberosity above the emargination, for it entirely corresponds with what in ruminants, pachyderms and many mammals would be named the coracoid process. If that process is accurately determined it is difficult to say what this is.

In birds there is often a prolonged process on the inner side of the coracoid, which however extends interior to other parts of the scapula, and to this the furculum is attached. Such traces of a spine as are to be detected in the swan conform to the Pterodactyle.

No bird has the scapula cylindrical, even struthious birds only making an approximation to such a condition; and no birds have the scapula so straight. The bone is more avian and mammalian than reptilian; and more avian than mammalian but with strong distinctive characters of its own.

17 specimens of the humeral ends of scapulæ are exhibited. Nos. 1, 4, 6, 7, 8, 9, 11, 13, 14, 15, 17 are left scapulæ. Nos. 2, 3, 5, 10, 12, 16 are right scapulæ.

The tablet of the distal ends of scapulæ comprises 6 specimens.

Fore-Limb.
HUMERUS.
[Pl. 4.]

There are among the fossils of the Cambridge Greensand at least two well-marked types of Pterodactyle humerus, readily recognised by the forms of the proximal and of the distal ends, and by the positions of the pneumatic foramina. In the group having the ulnar ridge developed the pneumatic foramen is on the posterior aspect of the bone[O] under the ulnar ridge, as in birds; but in some of the small Pterodactyles the foramen is on the anterior surface, and on its radial side. This latter kind of humerus has the distal end more or less divided into three convex surfaces, while the radial crest is enormously developed and terminates in a smooth oblong flattened surface nearly as large as the proximal articular surface, and looking anteriorly. The distal articular surfaces are not as in birds parallel to that of the proximal end, though they agree with those of birds in being at right angles to the radial crest; this ridge in Pterodactyles being directed much further outward and backward than in birds.

[O] Professor Owen states (p. 16, 3d Supt.) that the foramen is palmar. Fig. 15. T. III. 2d Supt. shows it to be anconal.

The largest forms of Pterodactyle all have the distal articular surface flatter, and the proximal articulation less bent back so as to look more upwards. No specimen of this kind of humerus has occurred with the radial crest preserved; but it is apparently carried farther down the shaft and not so far forward as in the other group. This latter kind of bone is shown by Prof. Owen in T. III. figs. 1, 2, 3rd Sup. Cret. Reptiles; the former kind has been illustrated in figure 5 of the same plate.

Some of the most gigantic Pterodactyles appear to have had the limb-bones as solid as those of crocodiles, and unpermeated by air; and there is no evidence that the high Avian characteristics of most of these Greensand fossils also pertained to all the previously known types from the lower secondary rocks.

The osteological series comprises 46 specimens. No. 30 is a nearly perfect right humerus. Nos. 1, 2, 5, 6, 7, 8, 9, 11, 18, 22, 23, 25, 39 are examples of the proximal ends of left humeri. Nos. 3, 4, 10, 12, 13, 14, 15, 16, 17, 19, 24, 26, 27, 28, 38, 40, 41 are examples of the proximal ends of right humeri. Nos. 20, 21, 32, 33, 34, 35, 37, 42, 44, 45, are examples of the distal ends of left humeri. Nos. 29, 31, 36, 43 and 46 are distal ends of right humeri.

No. 30 shows the entire length of the humerus to be 2¹/₂ inches. It has a nearly circular shaft with a diameter of a little more than a quarter of an inch, being more slender than the corresponding bone of Pt. suevicus, which has the same length. The proximal articular surface is crescentic, the anterior concavity corresponding with the concave anterior aspect of the proximal end, while the convex border corresponds to the convex posterior side of the bone, which it overhangs: it is worn, but appears to measure half an inch from the radial to the ulnar side. The ulnar ridge (which is worn) has not extended more than a quarter of an inch beyond the articular surface. The thin bird-like radial crest, arising rather more distally than the ulnar ridge, is flat on its posterior surface, and extends anteriorly for a distance nearly half as far again as the length of the proximal articular surface of the humerus. On the proximal third of the posterior face are two contiguous long narrow oblique muscular insertions. The proximal ends Nos. 22, 23, 24, 25 are examples of this kind of bone, having the pneumatic foramen radially situated on the anterior aspect near to the articular surface, as may be seen in No. 24. No. 25 shows the termination of the radial crest in an oblique oblong smooth surface, slightly convex in length and breadth, directed distally towards the ulnar side.

No. 6, 7, 13, 27, are examples of another kind of proximal end, where the pneumatic foramen is an oval hole on the ulnar side of the posterior surface. The radial crest arises more distally, and the ulnar ridge more proximally, than in the small species, like No. 30.

Nos. 4, 11, 14, 16 are examples of other species with the foramen placed as in the last group, only less near to the proximal end, while it enters obliquely, being directed distally from the broad concave area proximal to it. The largest proximal ends known, such as No. 2, which though very imperfect measures 2³/₄ inches over what remains of the articular surface, appear to conform to this latter type.

Distally the humerus No. 30 enlarges, widening rapidly on the radial side, which is bordered near the distal end by a sharp ridge showing a muscular attachment, while the ulnar side is rounded and rather inflated. The articular surface looks downward and in the direction of the radial process. There is a mesial concavity on the radial side which is bordered on the right and on the left by a prominent rounded condyle, and behind by a condyloid convexity. On that side which in conformity with the nomenclature applied to birds' bones, has here been named the ulnar side, the ulnar and mesial condyles are impressed with a flattened slightly concave sub-rhomboid area, which looks downward, backward, and towards the ulnar side. These characters are not well seen in No. 30, but may be effectively studied in their specific variations in Nos. 36, 37, 42, 43, 44, 45, and 46.

Nos. 20, 21, 29, 31, 32, 33, 34, 35, are examples of the distal ends of humeri of a different type. They are mostly larger than the preceding group, and correspond in characters with the large proximal ends, but appear to be separable into two groups, namely those with a pneumatic foramen on the anterior radial side near to the articular surface, and those where no pneumatic foramen is seen. Unlike the previously considered type, the ulnar side is sometimes more inflated than the radial side.

The mesial condyle in this group appears in every case to be an epiphysis, which is wanting. The radial condyle becomes a large flattened slightly convex surface looking downwards, which in some of the species, as Nos. 21 and 32 (in other respects remarkable species), shows an approach to a trochlear character on its anterior side. In Nos. 33, 34 and 35 the mesial anterior concavity becomes flattened and abuts at an angle against the flattened radial condyle. No. 20 shows the rhomboid impression on the ulnar side to be more concave and more ovate. The ulnar condyle remains a smaller but prominent tubercle directed distally. Nos. 21, 22 and 34 show a ridge developed on the ulnar side of the shaft like that on the radial side in the other group, while the radial ridge is not so near to the articular surface. The largest and smallest distal ends of humeri known, both show the characters here enumerated. The great distal end of a left humerus, figured by Prof. Owen, Pl. IV. f. 1, 2, 3 of the 1st Supplement to the Cretaceous Pterosauria, is of this kind, and though imperfect measures more than three inches over what remains of the articular surface. In the small humerus, No. 30, the width over the distal articular surface is ⁵/₈ths of an inch. If it is assumed that the large bone was no more than 5 times the length of the small one, the entire length of the humerus would have been about twelve inches. The smallest humerus, No. 29, measures over the shaft rather more than one eighth of an inch.

The Ornithosaurian humerus has but little in common with that of any mammal. Most mammals have the proximal head of the bone hemispherical, and a pit at the distal end for the olecranon process of the ulna, while there is usually little indication of a radial crest, and the proximal and distal ends are in the same plane. In the Bat however the bone is twisted a little so that the slight radial crest looks in the same direction as the distal end, here also there is no pit for the olecranon; but the bone is sigmoid and proportionally much longer than in Pterodactyles. In the horse, hippopotamus, &c., the radial process becomes more developed but never resembles that of a Pterodactyle.

Among reptiles, the bone may be compared with lizards and crocodiles. In crocodiles the proximal and distal ends are nearly in the same plane, the distal end has two condyles, the head is convex from side to side, and the radial crest is moderately developed and never extends so far outward or so far proximally as in Pterodactyle. In the Chameleon the bone is more twisted than in Crocodile, and as in Pterodactyle the distal end is compressed on the radial side to a sharp margin. In Iguana, Scink, and Monitor both proximal and distal ends are much expanded, and the radial process makes no approximation to that of a Pterodactyle.

The bird humerus does not approximate more closely in form to that of the Pterodactyle than does the Chameleon humerus, though it has the cardinal distinction of pneumatic foramina, and these sometimes corresponding in position in the two groups.

The bird humerus is commonly longer, though in the parrots the proportions and straightness are not unlike Pterodactyle. In some respects a nearer resemblance is seen in the raptorial bird Gypogeranus serpentarius, in which the radial process is rather more developed than in the Crocodile, and extends further proximally though still much smaller than in Pterodactyle; here too the superior surface is concave from side to side, and the distal articulation is not unlike that of some Pterodactyles. But no Pterodactyle has the head of the humerus convex from the radial to the ulnar sides, and the bird is distinctive in having the ulnar crest developed on the inferior side of the head: a faint approximation to a similar development is seen in Crocodile, but there is no trace of such a process in Pterodactyle. The distal end is more Bird-like than Lacertian in form, but is twisted to a greater angle with the proximal end than in birds.

Altogether the bone is distinctive. The points in which it is unlike birds and reptiles are those in which Birds and Lizards resemble each other; it would not be easy to say that in form it resembles one group more than the other. But it is linked with birds by the pneumatic foramina.

RADIUS AND ULNA.

Of neither of these bones has a perfect specimen been found. While fragments of humeri are met with frequently, fragments of these bones are rare. In accordance with the analogy with birds the Ulna might be presumed to be the larger bone of the two. But from a study of German specimens the larger bone is found to be the Radius, which according to the mammalian plan is placed in front of the ulna. As a whole, the fore-arm of Ornithosaurians is only to be compared with the insectivorous mammal Chrysochloris Capensis, in which there are also three bones in the fore-arm,—the third bone like the Pteroid bone in Ornithosaurians, extending about half-way from the carpus to the humerus, and holding, relatively, a similar position and development to the fibula in bats.

The pteroid bone articulated with a separate carpal, and was placed on the side of the arm, adjacent to the radius, which at the distal end extended in German specimens more inward than the ulna. In Chrysochloris the third bone appears to be behind the other bones, and adjacent to the ulna[P].

[P] See D'Alton and Pander Chiropteren und Insectivoren, Bonn, 1831, pl. 5, Chrysochloris.

Among neither birds nor reptiles is any comparable modification of the fore-arm to be found. Then by examining the proximal surface of the proximal carpal, the characters of the distal end of the Radius are readily discovered. The proximal carpal shows on the same surface another articular facets with which however only one fragmentary distal end of a bone corresponds. That accordingly is identified as the ulna. Besides these, three other articular ends of bones occur, one of which fits on to the distal end of the femur. The remaining two are both large bones, with epiphyses which formed portions of the articular surfaces, and are usually wanting. One of these bones corresponds in form with the ulna of a bird, and would fit the facet on the ulnar side of the distal end of the Pterodactyle humerus. The other bone is massive with a sub-quadrate articular end, and might well be the proximal end of the radius. Some specimens are among the largest fragments of Pterodactyle bone known. The only other bone that either of these could be is the distal end of the tibia, a bone not yet known, but probably not unlike that of a bird.

I. Distal End of Ulna.

Four specimens which show articular ends such as the ulna should have, are mounted together. They are compressed bones with the section of the fracture elongately oval; and the shaft widens from the fracture to the articulation without increasing in thickness. The outer surface is gently convex, becoming concave mesially near the articulation; the inner surface has the same characters, only the concavity at the extreme distal end reaches from side to side of the bone. The two short sides both look outward as well as laterally; one of them flattened so as to thicken the bone, is concave in vertical outline owing to the extreme distal end turning suddenly outward; the other side a little convex, compresses the bone and inflects its inner margin. The longest specimen measures 1⁵/₈ inch; ⁵/₈ inch wide at the fracture, and 1¹/₈ inch wide at the distal end. The greatest thickness at the distal end is half an inch, the thickness of the fractured shaft is ⁵/₈ of an inch.

The articular surface appears to have an elongated sub-reniform shape, the part at the compressed side of the bone being narrower than the broad ovate part on the thick side of the bone, to the lateral limit of which it extends, while the narrow part does not extend laterally nearly so far as the inflected border, which appears to give attachment to powerful muscles. There is also a strong muscular attachment at the corresponding diagonal corner of the bone where the outer surface on its right meets the side of the bone in an elevated ridge.

In its long diameter the articulation is a little convex; transversely it is very convex in the ovate part, but more flattened in its narrower continuation. Where widest it measures about ⁴/₁₀ths of an inch.

Nos. 5 and 6 on another tablet appear to be distal ends of ulna of another kind of Pterodactyle. They are less compressed, more quadrate in section, and have the sides more nearly parallel The flattened side similarly has a concave border, but instead of having its distal termination developed laterally, has it thickened behind. The opposite side of the bone which in the other specimens was compressed is here thick and well rounded, and not at all inflected. There is an absence of the concavity noticed on the outer surface of the bone in the compressed specimens. The articular surface is much flatter, and a little concave in length instead of being convex; as in the other examples it looks downward. The largest fragment. No. 5, measures 1³/₈ inch long; it is ⁶/₈ inch wide at the fracture, and ⁴/₈ inch thick. The sub-quadrate distal end is more than an inch long, more than ⁴/₈ths inch thick on the thick side, and nearly ⁴/₈ths inch thick on the compressed side.

II. Distal End of Radius.

The best preserved of the 10 specimens here exhibited is 3 inches long, No. 2. The shaft is oval, flattened on one side; measuring at an inch from the fractured end ⁷/₁₀ths of an inch in the least diameter, and one inch in the wide diameter. It widens distally at first slowly, then rapidly, till at the articular end its greatest width is two inches. But while expanding laterally it contracts from side to side, the more convex side of the two at about an inch from the articular end, beginning to approximate to the flatter side till the articular end has a short diameter of less than half an inch.

On the left-hand corner of the convex inner side of the bone is an elevated flattened disc for muscular attachments, fully half an inch in diameter, there is a slight muscular attachment interior to this, nearer the middle of the bone. The left-hand corner of the flattened outer side of the distal end of the radius is marked by a vertical ridge bordering a similarly elevated oval muscular attachment. Parallel to this nearer the middle of the side is a much stronger and acutely elevated ridge.

The articulation is made up of three distinct parts, all in a straight line. The portion of bone adjacent to the large muscular disc is compressed and rounded on the distal end; then first there is a rather deep circular cup ³/₈ths of an inch wide, nearer to the more convex than to the flatter side of the bone; adjacent to this cup is a convex ball of about the same size; while the remainder of the articulation is concave in length, convex from side to side, and looks downward and a little towards the inner convex side of the bone. The specimens are arranged so as to display these characters.—The example described is of nearly the same size as that figured for the humerus in fig. 1, T. XXIV. of the Cretaceous Reptilia. The less well preserved bone in that figure exhibits the Ulna in its true position behind the Radius.

III. Proximal End of Ulna.

This bone has much the proportions of the Ulna in birds, the smaller specimens nearly resembling the ulna of the Heron. The specimen (No. 1) with the shaft best preserved is 2¹/₄ inches long, cylindrical at the fracture, where it measures in diameter ³/₁₆ths of an inch. It gradually enlarges proximally widening to about ⁷/₁₀ths of an inch; near the proximal end it is a little curved, the side which is concave in length being a little flattened, while there is a lateral elevation on the opposite side, apparently corresponding to the quill-ridge on the convex side of the bird-ulna. There is a separate ossification for the olecranon, which is an irregular sub-oblong bone forming the outer part of the articulation; it is only preserved in No. 1. Nos. 4, 5 and 6 show the concave transverse groove from which it has come away.

The articular surface looks upward and forward, in which aspect it has a trapezoidal form. Sometimes, as in No. 2, the great sigmoid area is divided into two parts by a vertical ridge, the more elevated part of the articulation on the radial side of the bone being concave, while the outer part, as in the heron, besides being concave, has its border on the concave side of the bone produced and rounded. There is a small triangular elevation on the radial aspect of the proximal end like that on the corresponding part of the ulna of the heron. On this aspect the bone is flattened, on the opposite and outward aspect it is compressed and produced as in the bird. No. 2 measures 1¹/₈ inch over the articular end. The series includes 6 specimens.

IV. Proximal End of Radius.

This bone terminated in an epiphysis which formed part of the articular surface, and has disappeared from all the 7 specimens mounted. So much of the articulation as remains does not oppose the idea of its having been attached to the humerus, while the large size of the example No. 7, which could not have measured less than 2¹/₂ inches from side to side over the articulation, is more in accordance with what is at present known of the dimensions attained by the distal end of the humerus than with the size that would be expected in the distal end of the tibia, which is the only other unknown bone to which these specimens could be referred.

The longest specimen, No. 3, is 3 inches long; broadly ovate at the fracture, measuring in the long diameter 1 inch, and in the short diameter more than ³/₄ths of an inch. Nearer the articular end the bone becomes in section sub-quadrate or rather sub-rhomboid. No. 1 shows these terminal characters extremely well. On the posterior aspect of the specimen the surface is divided into two flattened slightly convex parts by a median vertical well-rounded angular bend. In front the side is similarly divided into two parts, both of them a little concave proximally, by a sharp median vertical ridge, which does not reach to the articulation by a varying distance, never so long as the bone is wide. The ridge terminates in, and is pierced by, a vertical groove apparently for a nutritive vessel. Where the anterior and posterior aspects of the bone converge laterally the sides are well rounded.

Only a small part of the articular surface is preserved, looking upward and a little forward; it terminates the wider of the halves of the bone laterally and in front. The remainder of the articular surface, from which the epiphysis has come away, may be divided principally in the majority of specimens into a posterior flattened median rhomboid space and an oblong cup-shaped anterior space divided from it by an elevated ridge. The extreme lateral termination appears to have been a ball-shaped convexity.

The great length of the fore-arm relatively to the humerus, characteristic of German Ornithosaurians, from the fragmentary condition of Cambridge specimens is not seen.

Although the fore-arm resembles Chrysochloris in plan the resemblance is not close in the details of form. In many Mammals it is characteristic for the radius to be the principal bone of the fore-arm, and among Ruminants in which this is especially the case the radius is altogether in front and the ulna behind as is the position with Birds and Crocodiles. And among mammals with claws, as in the Lion, Bear, &c., and in the Chameleon, it is characteristic, for the radius also to be on the inside of the limb at the distal end, as in Ornithosaurians. In form, ridges, and muscular attachments (see pl. 3) the distal end of the radius approximates closely to the Bear and the Lion, and may also be compared with the Bats and Birds, though with Birds it is a small bone. From the epiphysis of the proximal end apparently being wanting it would be difficult to compare closely. But though not like any particular mammal, it might have pertained to a mammal since it has the large perforation for the nutritive vessel near to the proximal end as in the Camel and many of the mammalia.

The ulna of the Pterodactyles is at the proximal end altogether distinguished from mammals by the slight development of the olecranon, nor can the distal end, especially in its relation to the carpus, be paralleled.

Among birds and reptiles the ulna is the large bone, and here a general resemblance in form to the ulna of Pterodactyles is seen at the proximal end. It is not compressed from side to side as in the Crocodile, Iguana, Monitor, &c., but from back to fronts in this rather resembling Birds than the Chameleon. It however at the distal end is more crocodilian.

The fore-arm in plan is mammalian. The Pteroid bone is mammalian, the Radius is mammalian and avian; the Ulna is avian, and crocodilian in form, but mammalian in proportion. The pneumatic foramen of the ulna is peculiarly avian.

CARPUS.
[Pl. 5.]