 CHAPTER VIII. OF DRAGONS OF THE AIR, by Harry Seeley. While these animals are incontestably nearer to birds than to any other animals in their plan of organization, thus far no proof has been found that they are birds, or can be included in the same division of vertebrate life with feathered animals. It is one of the oldest and soundest teachings of Linnaeus, that a bird is known by its feathers, and the record is a blank as to any covering to the skin in pterodactyls. There is the strongest probability against feathers having existed such as are known in the Archaeopteryx, because every Solenhofen or Nithosaur appears to have the body devoid of visible or preservable covering, while the two birds known from the Solenhofen slate deposit are well clothed with feathers in perfect preservation. We turn from the skin to the skeleton. The plan on which the skeleton is constructed remains as evidence of the animal's place in nature, which is capable of affording demonstration on which absolute reliance would have been placed if the brain and pneumatic foramenah had remained undiscovered. With the entire skeleton before us, it is inconceivable that anatomical science should fail to discover the true nature of the animal to which it belonged by the method of comparing one animal with another. There is no lack of this kind of evidence of pterodactyls in the three or four scores of skeletons and thousands of isolated or associated bones preserved in the public museums of Europe and America. I may recall the circumstance that the discovery of skeletons of fossil animals has occasionally followed upon the interpretation of a single fragment from which the animal has been well defined and sometimes accurately drawn before it was ever seen. So I propose, before drawing any conclusions from the skeletons in the entirety of their construction, to examine them bone by bone and region by region for evidence that will manifest the nature of this brood of dragons. They're living kindred and perhaps their extinct allies, assembled as a jury, may be able to determine whether resemblances exist between them and whether such similarity between the bones as exists is a common inheritance or is a common acquisition due to similar ways of life and no evidence of the grade of the organism among vertebrate animals. The bones of these ornithosaurs, when found isolated, first have to be separated from the organisms with which they are associated and mixed in the geological strata. This discrimination is accomplished in the first instance by means of the texture of the surface. The density and polish of the bones is even more marked than in the bones of birds and is usually associated with a peculiar thinness of substance of the bone, which is comparable to the condition in a bird, though usually a little stouter, so that the bones resist crushing better. Pterodactyl bones in many instances are recognized by their straightness and comparatively uniform dimensions, due to the exceptional number of long bones which enter into the structure of the wing as compared with birds. When the bones are unerringly determined as ornithosaurian, they are placed side by side with all the bones which are most like them, till, judged by the standard of the structures of living animals, the fossil is found to show a composite construction as though it were not one animal, but many, while its individual bones often show equally composite characters. As though parts of the corresponding bone in several animals had been cunningly fitted together and molded into shape. The plan of the head in ornithosaur. The head is always the most instructive part of an animal. It is less than an inch long in the small sullenholfen skeleton named pterodactylis brevirostris, and is said to be three feet nine inches long in the toothless pterodactyl or nithostoma from the chalk of Kansas. Most of these animals have a long slender conical form of head, tapering to the point like the beak of a heron, forming a long triangle when seen from above or from the side. Sometimes the head is depressed in front, with the beak flattened or rounded as in a duck or goose, and occasionally in some wielden and greensand species, the jaws are truncated in front in a massive snout quite unlike any bird. The back of the head is sometimes rounded as among birds, showing a smooth, pear-shaped posterior convexity in the region of the brain. Sometimes the back of the head is square and vertical or oblique. Occasionally a great crest of cellular tissue is extended backward from above the brain case over the spines of the neck bones. There are always from two to four lateral openings in the skull. First, the nostril is nearest to the extremity of the beak. Secondly, the orbits of the eyes are placed far backward. These two openings are always present. The nostril may incline upward. The orbits of the eyes are usually lateral, though their upper borders sometimes closely approximate, as in the woodpecker-like types from the solenhofen slate, named pterodactylus cocci, now separated as another genus. In most genera there is an opening in the side of the head between the eye-hole and the nostril, known as the antorbital vacuity. And another opening, which is variable in size and known as the temporal vacuity, is placed behind the eye. The former is common in the skulls of birds. The latter is absent from all birds and found in many reptiles. The palate is usually imperfectly seen, but English and American specimens have shown that it has much in common with the palate in birds, though it varies greatly in form of the bones and representatives from the lias, oolites, and cretaceous rocks. From the scientific aspect, the relative size of the head, its form, and the positions and dimensions of its apertures and processes, are of little importance in comparison with its plan of construction as evidenced by the positions and relations to each other of the bones of which it is formed. There usually is some difficulty in stating the limits of the bones of the skull, because in pterodactyls, as among birds, they usually blend together, so that in the adult animal the sutures between the bones are commonly obliterated. Bones have relations to each other and places in the head which can only change as the organs with which they are associated change their positions. No matter what the position of a nostril may be, at the extremity of a long snout, as in an anteater, or far back at the top of the head in a porpoise, or at the side of the head in a bird, it is always bordered by substantially the same bones which vary in length and size with the changing place of the nostril and the form of the head. Every region of the head is defined by this method of construction, so that eye holes and nose holes, brain case and jaw bones, palate and teeth, beak and back of the skull are all instructive to those who seek out the life history of these animals. We may briefly examine the head of an ornithosarion. Bones About the Nostril No matter what its form may be, the head of an ornithosaur always terminates in front in a single bone called the intermaxillary. It sends a bar of bone backward above the visible nostrils between them, and a bar on each side forms the margin of the jaw in which teeth are implanted. The bone varies in depth, length, sharpness, bluntness, slenderness, and massiveness. As the bone becomes long, the jaw is compressed from side to side, and the openings of the nostrils are removed backward to an increasing distance from the extremity of the beak. The outer and hinder border of the nostril is made by another bone named the maxillary bone, which is usually much shorter than the premaxillary. It contains the hindermost teeth, which rarely differ from those in front, except in sometimes being smaller. The nasal bones, which always make the upper and hinder border of the nostrils, meet each other above them in the middle line of the beak. The nostrils are unusually large in the liest genus named dimorphodon, and small in species of the genus ramphorencus from Solenhofen. Such differences result from the relative dimensions and proportions of these three bones, which margin the nasal vacuity, and by varying growth of their front margins, or of their hinder margins, govern the form of the snout. The jaws are most massive, in the genera known from the wielden beds to the chalk. The palatal surface is commonly flat or convex, and often marked by an elevated median ridge, which corresponds to a groove in the lower jaw, though the median ridge sometimes divides the palate into two parallel concave channels. The jaw is margined with teeth, which are rarely fewer than ten, or more than twenty on each side. They are sharp, compressed from side to side, curved inward, and never have a saw-like edge on the back and front margins. No teeth occur upon the bones of the palate. In most birds there is a large vacuity in the side of the head between the nostril and the orbit of the eye, partly separated from it by the bone which carries the duct for tears, named the lacrimal bone. The same pre-orbital vacuity is present in all long-tailed pterodactyls, though it is either less completely defined or absent in the group with short tails. It affords excellent distinctive characters for defining the genera. In the long-tailed genus scaphonaphis from Solenhofen, this pre-orbital opening is much larger than the nostril, while in dimorphodon these vacuities are of about equal size. Rampharencus is distinguished by the small size of the ant-orbital vacuity, which is placed lower than the nostril on the side of the face. The aperture is always imperfectly defined in pterodactyls, and is a relatively small vacuity compared with the long nostril. In tenodrachan, the ant-orbital vacuity appears to have no existence separate from the nostril which adjoins the eye-hole. And so far as is known at present there is no lateral opening in advance of the eye in the skull and any ornithosaur from cretaceous rocks, though the toothless ornithostoma is the only genus with the skull complete. When a separate ant-orbital vacuity exists, it is bordered by the maxillary bone in front and by the mallar bone behind. The prefrontal bone is at its upper angle. That bone is known in a separate state in reptiles, and I think in monotreme mammals. Its identity is soon lost in the mammal, and its function in the skull is different from the corresponding bone in pterodactyls. Bones About the Eyes The third opening in the side of the head, counting from before backward, is the orbit of the eye. In this vacuity is often seen the sclerotic circle of overlapping bones formed in the external membrane of the eye like those in nocturnal birds and some reptiles. The eye-hole varies in form from an inverted pear shape to an oblique or transverse oval or a nearly circular outline. It is margined by the frontal bone above, the tear bone or lacrimal, and the mallar or cheek bone in front. While the bones behind appear to be the quadrato-juggle and post-frontal bones, though the bones about the eye are somewhat differently arranged in different genera. The eyes were frequently, if not always, in contact with the anterior walls of the brain case, as in many birds, and are always far back in the side of the head. In dimorphodon they are in front of the articulation of the lower jaw, in ramphorincus above that articulation. While in ornithostoma they are behind the articulation for the jaw. This change is governed by the position of the quadrate bone, which is vertical in the lios genus, inclined obliquely forward in the fossils from the oolites, and so much inclined in the chalk fossil that the small orbit is thrown relatively further back. Thus far the chief difference in the pterodactyl skull from that of a bird is in the way in which the mallar arch is prolonged backward on each side. It is a slender bar of bone in birds, without contributing ascending processes to border vacuities in the side of the face. While in these fossil animals the lateral openings are partly separated by the ascending processes of these bones. This divergence from birds in the mallar bone entering the orbit of the eye is approximated to among reptiles and mammals, though the conditions and perhaps the presence of a bone like the post orbital bone are paralleled only among reptiles. The pterodactyls differ among themselves enough for the head to make a nearer approach to reptiles in dimorphodon and to birds in pterodactyls. In the ground hornbill and the shoebill the lacrimal bones in front of the orbits of the eyes grow down to meet the mallar bars without uniting with them. The post frontal region also is prolonged downward almost as far as the mallar bar as though to show that a bird might have its orbital circle formed in the same way and by the same bones as in pterodactyls. Cretaceous ornithosaurs sometimes differ from birds apparently in admitting the quadrato juggle bone into the orbit. It then becomes an expanded plate instead of a slender bar as in all birds. The temporal fossa. A fourth vacuity is known as the temporal fossa. When the skull of such a mammal as a rabbit or sheep is seen from above there is a vacuity behind the orbits for the eyes which in life is occupied by the muscles which work the lower jaw. It is made by the mallar bone extending from the back of the orbit and the process of bone called the zygomatic process extending forward from the articulation of the jaw which arches out to meet the mallar bone. In birds there is no conspicuous temporal fossa because the mallar bar is a slender rod of bone in a line with the lower end of the quadrate bone. Reptile skulls have sometimes one temporal vacuity on each side as among tortoises formed by a single lateral bar. These vacuities which correspond to those of mammals in position are seen from the top of the head as lateral vacuities behind the orbits of the eyes and are termed superior temporal vacuities. In addition to these there is often in other reptiles a lateral opening behind the eye termed the inferior temporal vacuity seen in crocodiles in hatteria and in lizards. And in such skulls there are two temporal bars seen inside view distinguished as superior and inferior. The superior arch always includes the squamosal bone which is at the back of the single bar in mammals. The lower arch includes the mallar bone which is in front in the single arch of mammals. The circumstance that both these arches are connected with the quadrate bone makes the double temporal arch imminently reptilian. In ornithosaurs the lateral temporal vacuity varies from a typically reptilian condition to one which without becoming avian approaches the bird type. In skulls from the lios dimorphodon and campylo nathus there is a close parallel to the living New Zealand reptile hatteria in the vertical position of the quadrate bone and in the large size of the vacuity behind and below the eye which extends nearly the height of the skull. In the species of the genus pterodactylus the forward inclination of the quadrate bone recalls the curlew, snipe and other birds. The back of the head is rounded and the squamosal bone which appears to enter into the wall of the brain case as in birds and mammals is produced more outward than in birds but less than in mammals so as to contribute a little to the arch which is in the position of the post frontal bone of reptiles. It is triangular and stretches from the outer angle of the frontal bone at the back of the orbit to the squamosal behind where it also meets the quadrate bone. Its third lower branch meets the quadrato juggle which rests upon the front of the quadrate bone as in iguanodon and is unlike dimorphodon in its connections. In that genus the super temporal bone or post orbital bone appears to rest upon the post frontal and connect it with the quadrato juggle. In dimorphodon the mallar bone is entirely removed from the quadrate but in pterodactylus it meets its articular end. Between the post frontal bone above and the quadrato juggle bone below is a small lunate opening which represents the lateral temporal vacuity and so far this is a reptilian character. But if the thin post frontal bone were absorbed pterodactylus would resemble birds. There's no evidence that the quadrate bone is free in any ornithosaurs as it is in all birds while in dimorphodon it unites by suture with the squamosal bone. In ornithostoma the lateral temporal vacuity is little more than a slit between the quadrate bone below the quadrato juggle in front and what may be the post frontal bone. Bones about the brain. The bones containing the brain appear to be the same as form the brain case in birds. The form of the back of the skull varies in two ways. First it may be flat above and flat at the back when the back of the head appears to be square. This condition is seen in all the long tailed genera such as campylo nappus from the lius and rampforencus and is associated with a high position for the upper temporal bar. Secondly the back of the head may be rounded convexly both above and behind. That condition is seen in the short tailed genera such as pterodactylus. But in the large cretaceous types such as ornithocaris and ornithostoma the superior longitudinal ridge which runs back in the middle line of the face becomes elevated and compressed from side to side at the back of the head as a narrow deep crest prolonged backward over the neck vertebrae for some inches of length. All these three types are paralleled more or less in birds which have the back of the head square like the heron or rounded like the woodpecker. Or crested though the crest of the cormorant is not quite identical with ornithocaris being a distinct bone at the back of the head in the bird which never blends with the skull. Insofar as the crest is reptilian it suggests the remarkable crest of the chameleon. In the structure of the back of the skull the bones are a modification of the reptilian type of Hatteria in the Lyus genus Campylo-Nathus but the reptilian characters appear to be lost in the less perfectly preserved skulls of cretaceous genera. The pallet is well known in the chief groups of ornithosaurs such as Campylo-Nathus, Skapha-Nathus, and Cycno-Ramphus. Mr. E.T. Newton, FRS, has shown that in the English skull from the Lyus of Whitby the forms of the bones are similar to the pallet in birds and unlike the conditions in reptiles. There is one feature however which may indicate a resemblance to Dysenodon and other fossil reptiles from South Africa. A slender bone extends from the base of the brain case named the basis phenoid bone outward and forward to the inner margin of the quadrate. A bone is found thus placed in those South African reptiles which show many resemblances to the monotreme and marsupial mammals. It is not an ordinary element of the skeleton and is unknown in living animals of any kind in that position. It has been thought possible that it may represent one of the bones which among mammals are diminutive and are included in the internal ear. The resemblance may have some interest hereafter as helping to show that certain affinities of the ornithosaurs may lie outside the groups of existing reptiles. Instead of being directed transversely outward as in the palatal region of Dysenodon Lyserticeps they diverge outward and forward to the inner border of the articulation for the lower jaw which is upon the quadrate bone. Bones of the pallet. There is a pair of bones which extend forward from these inner articular borders of the quadrate bones and converge in a long V shape till they merge in the hard pallet formed by the bones of the front of the beak named intermaxillary and maxillary bones. The limits of the bones of the pallet are not distinct but there can be no doubt that the front of the V is the bone named vomar that the palatine bones are at its sides and that its hinder parts are the pteragoid bones as in birds. There is a long wide four-sided open space in the middle of the pallet between the vomar and the basis phenoid bone unlike anything in birds or other animals. Professor Marsh in a figure of the pallet in the great skull of the toothless pterodactyl named ornithostoma pteranodon from the chalk of Kansas found a large oval vacuity in this region of the pallet. In that genus the pteragoid bones meet each other between the quadrate bones as in disinodon. Hence the great palatal vacuity here seen in the ornithosaur is paralleled by the small vacuity in the South African reptile which is sometimes distinct and sometimes partly separated from the anterior part of the vacuity which forms the openings of the nostrils on the pallet. The solenhofen skulls which give any evidence of the pallet are exposed in side view only and the bones imperfectly seen through the lateral vacuities are displaced by crushing. They include long strips like the vomarine bones in the lios fossil and they diverge in the same way as they extend back to the quadrate bones. The oblique division into vomar in front and pteragoid bone behind is shown by Goldfuss in his original figure of scaphonathus. Thus there is some reason for believing that all ornithosaurs have the pallet formed upon the same general plan which is on the whole peculiar to the group especially in not having the palatal openings of the nary's divided in the middle line. It would appear probable that the short-tailed animals have the pteragoid bones meeting in the middle line and triangular and that they are slender rods entirely separate from each other in the long tailed genera. The teeth. The teeth are all of pointed elongated shape without distinction into the kinds seen in most mammals and named incisors canines and grinders. They are organs for grasping like the teeth of the fish-eating crocodile of India and are not unlike the simple teeth of some porpoises. They are often implanted in oblique oval sockets with raised borders usually at some distance apart from each other and have the crown pointed flattened more on the outer side than on the inner side usually directed forward and curved inward. As in many extinct animals allied to existing reptiles the teeth are reproduced by germs which originate on the inner side of the root and grow till they gradually absorb the substance of the old tooth forming a new one in its place. Frequently in solenhofen genera like scaphonathis and pterodactylis the successional tooth is seen in the jaw on the hinder border of the tooth in use. There is some variation in the character of bluntness or sharpness of the crowns in the different genera and in their size. The name dimorphodon given to the animal from the liais of lime regis expresses the fact that the teeth are of two kinds. In the front of the jaw three or four large long teeth are found in the intermaxillary bone on each side as in some plesiosores while the teeth found further back in the maxillary bone are smaller and directed more vertically downward. This difference is more marked in the lower jaw than in the upper jaw. In ramphorincus the teeth are all relatively long and large and directed obliquely forward but absent from the extremities of the beak as in the german genus from the liais named dorinathis in which the bone of the lower jaw which alone is known terminates in a compressed spear. In scaphonathis the teeth are few more vertical and do not extend backward so far as in ramphorincus but are carried forward to the extremity of the blunt deep jaw. In the short tailed pterodactyls the teeth are smaller, shorter, wider at the base of the crown, closer together and do not extend so far backward in the jaw. In ornithocyrus two teeth always project forward from the front of the jaw. Ornithostoma is toothless. Supposid horny beak. Sometimes a horny covering has been suggested for the beak like that seen in birds or turtles but no such structure has been preserved even in the solenholfen slate in which such a structure would seem as likely to be preserved as a wing membrane though there is one doubtful exception. There are marks of fine blood vessels on some of the jaws indicating a tough covering to the bone. In ramphorincus the jaws appear to gape towards their extremities as though the interspace had originally been occupied by organic substance like a horny beak. Lower jaw. The lower jaw varies in relative length with the vertical or horizontal position of the quadrate bone in the skull. In dimorphodon the jaw is as long as the skull but in the genera from the oolitic rocks the mandible is somewhat shorter and in ornithostoma the discrepancy reaches its maximum. The hinder part of the jaw is never prolonged backward much beyond the articulation differing in this respect from crocodiles and plesiosores. The depth of the jaw varies. It is slender and pterodactylus and is probably stronger relatively to the skull in scaphonathus than in any other form. It fits between the teeth and bones of the alveolar border in the skull in all the genera. In dimorphodon its hinder border is partly covered by the descending edge of the mallar process which these animals develop in common with some dinosaurs and some anamodont reptiles and many of the lower mammals. In this hinder region the lower jaw is sometimes perforated in the same way as in crocodiles. That condition is observed in dimorphodon but is not found in pterodactylus. The lower jaw is always composite being formed by several bones as among reptiles and birds. The teeth are in the dentary bone or bones and these bones are almost always blended as in most birds and turtles and not separate from each other as among crocodiles, lizards and serpents. An interesting contour for the lower border of the jaw is seen in ornithostoma as made known in figures of American examples by professors Marsh and Williston. It deepens as it extends backwards for two-thirds its length, stops at an angle and then the depth diminishes to the articulation with the skull. This angle of the lower jaw is a characteristic feature of the jaws of mammals. It is seen in the monotreme echidna and is characteristic of some theriodont reptiles from South Africa which in many ways resemble mammals. The character is not seen in the jaws of specimens from the olytic rocks but is developed in the toothed ornithoceros from the Cambridge greensand and is absent from the jaws of existing reptiles and birds. Summary of characters of the head. Taken as a whole, the head differs from other types of animals in a blending of characters which at the present day are found among birds and reptiles with some structures which occur in extinct groups of animals with similar affinities and perhaps a slight indication of features common to the lowest mammals. It is chiefly upon the head that the diverse views of earlier writers have been based. Cuvier was impressed with the reptilian aspect of the teeth but in later times discoveries were made of birds with teeth. Archaeopteryx, Ictheornus, Hesperornus. The teeth are quite reptilian being not unlike miniature teeth of Mosesaurus. If those birds had been found prior to the discovery of pterodactyls the teeth might have been regarded as a link with the more ancient birds rather than a crucial difference between birds and reptiles. All the specimens show a lateral temporal hole in the bones behind the eye and this is found in no bird or mammal and is typical of such reptiles as Heteria. The quadrate bone may not be so decisive as Cuvier thought it to be for its form is not unlike the quadrate of a bird and different so far as I have seen from that of living reptiles. This region of the head is reptilian and if it occurred in a bird the character would be as astonishing as was the discovery of teeth in extinct birds. These characters of the head are also found in fossil animals named dinosaurs in association with many resemblances to birds in their bones. The palate might conceivably be derived from that of Heteria by enlarging the small opening in the middle line in that reptile till it extended forward between the vomora. But it is more easily compared with a bird which the animal resembles in its beak and in the position of the naries. Accepting certain lizards all true existing reptiles have the nostrils far forward and bordered by two premaxillary bones instead of one intermaxillary as in birds and ornithosaurs. If nothing were known of the animal but its head bones it would be placed between reptiles and birds. End of Chapter 8 Chapter 9 of Dragons of the Air by Harry Seeley This LibriVox recording is in the public domain. The backbone or vertebral column. The backbone is a more deep-seated part of the skeleton than the head. It is more protected by its position and has less varied functions to perform. Therefore it varies less in distinctive character within the limits of each of the classes of vertebrate animals than either the head or limbs. It is divided into neck bones, the cervical vertebrae, back bones, the dorsal vertebrae, loin bones, the lumbar vertebrae, the sacrum or sacral vertebrae which support the hind limbs, and the tail. Of these parts the tail is the least important though it reaches a length in existing reptiles which sometimes exceeds the whole of the remainder of the body and includes hundreds of vertebrae. It attains its maximum among serpents and lizards. In frogs it is practically absent. In some of the higher mammals it is a rudiment which does not extend beyond the soft parts of the body. The neck. The neck is more liable to vary than the back with the habit of life of the animal. And although mammals almost always preserve the same number of seven bones in the neck, the bones vary in length between the short condition of the porpoise in which the neck is almost lost and the long bones which form the neck of the yama though even these may be exceeded by some fossil reptiles like tenastrophius. In many mammals the neck bones do not differ in length or size from those of the back. In others like the horse and ox they are much broader and larger. There is the same sort of variation in the bones of the neck among birds, some being slender like the heron, others broad like the swan. But there is also a singular variation in number of vertebral bones in a bird's neck. At fewest there are nine which equals the exceptionally large number found among mammals in the neck of one of the sloths. Usually birds have 10 to 15 cervical vertebrae and in the swan there are 23. Most of the neck bones of birds are relatively long and the length of the neck is often greater than the remainder of the vertebral column. Reptiles usually have short necks. The common turtle has eight bones in the neck, ten in the back. The two regions are sharply defined by the dorsal shield. Their articular ends are sometimes cupped in front in the neck, sometimes cupped behind or convex at both ends, or even flattened, or the articulation may be made exceptionally by the neural arch alone. Nine is the largest number of neck bones in existing lizards, and there are usually nine in crocodiles, so that reptiles closely approach mammals in number of the neck bones. It is remarkable that the maximum number in a mammal and in living reptiles should coincide with the minimum number in birds. Therefore the number of cervical vertebrae as an attribute of mammal, bird, or reptile can only be important from its constancy. German naturalists affirm on clear evidence that the solenholfen pterodactyls have seven cervical vertebrae. In many specimens there can be no doubt about the number, because the neck bones are easily distinguished from those of the back by their size, but the number is not always easy to count. As in birds the first vertebra, or atlas, in pterodactyls is extremely short, and is generally, if not always, blended with the much longer second vertebra named the axis. The front of the atlas forms a small rounded cup to articulate with the rounded ball of the basioccipital bone at the back of the skull. The third and fourth vertebrae are longer, but the length visibly shortens in the sixth and seventh. Sometimes the vertebrae are slender and devoid of strong spinous processes. This is the condition in the little pterodactyls lingerostris, and in the comparatively large sycnoramphus phrasii, in which there is a slight median ridge along the upper surface of the arch of the vertebra. This condition is paralleled in birds with long necks, especially wading birds, such as the heron. Other ornithosaurs, such as ornithocaris, from the cretaceous rocks, have the neck much more massive. The vertebrae are flattened on the underside. The arch above the nervous matter of the spinal cord has a more or less considerable transverse expansion, and may even be as wide as long. These vertebrae have proportions and form such as may be seen in vultures or in the swan. In either case the form of the neck bones is more or less bird-like, and the neural spine may be elevated, especially in pterodactyls with long tails. One of the most distinctive features of the neck bones of a bird is the way in which the cervical ribs are blended with the vertebrae. They are small, and each is often prolonged in a needle-like rod at the side of the neck bone. In ornithocaris the cervical rib similarly blends with the vertebra by two articulations, as in mammals, so that it might escape notice, but for the channel of a blood vessel which is thus enclosed. In several of the older pterodactyls from Solenhofen the ribs of the neck vertebrae remain separated, as in a crocodile, though still bird-like in their form, anterior position, and mode of attachment. In pteropens and tortoises the long neck vertebrae have no cervical ribs. The articular surfaces between the bodies of the vertebrae in the neck are transversely oval. The middle part of this articular joint is made by the body of the vertebra. Its outer parts are in the neural arch. In front this surface is a hollow channel, often more depressed than in any other animals. The corresponding surface behind is convex, with a process on each side at its lower outer. It is a modification of the cup and ball form of vertebral articulation, which at the present day is eminently reptilian. Serpents and crocodiles have the articulations similarly vertical, but in both the form of the articulation is a circle. In lizards the articular cup is usually rather wider than deep when the cup and ball are developed in the vertebrae. It differs from the vertical condition in pterodactyls in being oblique and much narrower from side to side. Only among crocodiles and heteria is there a double articulation for the cervical rib, though in neither order have rib or vertebrae in the neck the bird-like proportions which are usual in these animals. Pterodactyls show no resemblance to birds in this vertebral articulation. A bird has the corresponding surface concave from side to side in front, but it is also convex from above downward, producing what is known as the saddle-shaped form, which is peculiarly avian, being found in existing birds except in part of the back in penguins. It is faintly approximated to in one or two neck vertebrae in man. Professor Williston remarks that in the toothless pterodactyls of Kansas, the hinder ball of the vertebral articulation is continued downward and outward as a concave articulation upon the processes at its outer corners. There are no mammals with a cup and ball articulation between the vertebrae, so that for what it is worth the character now described in ornithosaurs is reptilian when judged by comparison with existing animals. Low down on each side of the vertebra at the junction of its body with the neural arch is a large ovate foramen, transversely elongated and often a little impressed at the border, which is the entrance of the air cell into the bone. These foramina are often one-third of the length of the neck vertebrae in specimens from the Cambridge green sand, where the neck bones vary from three quarters of an inch to about two and a half inches in length, and in extreme forms are as wide as long. The width of the interspace between the foramina is one-half the width of the vertebrae, though this character varies with different genera and species. Several species from the sullenhofen slate have the neck long and slender on the type of the flamingo. In others the neck is thick and short, in the scaphonathus crassarostris and pterodactylus spectabilis. Some genera with slender necks have the bones preserved with a curved contour, such as might suggest a neck carried like that of a yama or a camel. The neck is occasionally preserved in a curve like a capital S, as though about to be darted forward like that of a bird in the act of striking its prey. The genera of pterodactyls with short necks may have had as great mobility of neck as is found among birds named ducks and divers. But those pterodactyls with stout necks, such as dimorphodon and ornithochiris, in which the vertebrae are large, appear to have been built more for strength than activity, and the neck bones have been chiefly concerned in the muscular effort to use the fighting power of the jaws in the best way. The back The region of the back in a pterodactyl is short as compared with the neck and relatively is never longer than the corresponding region in a bird. The shortness results partly from the short length of the vertebrae, each of which is about as long as wide. There is also a moderate number of bones in the back. In most skeletons from Solenhofen, these vertebrae between the neck and girdle of hip bones number from twelve to sixteen. They have a general resemblance in form to the dorsal vertebrae in birds. The greatest number of such vertebrae in birds is eleven. The number is small because some of the later vertebrae in birds are overlapped by the bones of the hip girdle which extend forward and cover them at the sides so that they become blended with the sacrum. This region of the skeleton in the dimorphodon from the lyus is remarkable for the length of the median process named the neural spine which is prolonged upward like the spines of the early dorsal vertebrae of horses, deer, and other mammals. In this character they differ from living reptiles and parallel some dinosaurs from the wheeled. The bones of the back in Ornithocaris from the Cambridge greensand show the underside to be well rounded so that the articular surfaces between the vertebrae, though still rather wider than deep, are much less depressed than in the region of the neck. The neural canal for the spinal cord has become larger and higher and the sides of the bone are somewhat compressed. Strong transverse processes for the support of the ribs are elevated above the level of the neural canal at the sides of vertebrae compressed on the undersides and directed outward. Between these lateral horizontal platforms is the compressed median neural spine which varies in vertical height. The articulation of the ribs is not seen clearly. Isolated ribs from the stonesfield slate have double-headed dorsal ribs like those of birds. In some specimens from the Solenhofen slate like the scaphonathus in the University Museum at Bonn, dorsal ribs appear to be attached by a notch in the transverse process of the dorsal vertebra which resembles the condition in crocodiles. Variations in the mode of attachment of ribs among mammals may show that character to be of subordinate importance. Von Meyer has described the first pair of ribs as frequently larger than the others, and they appear in Rampharencus to be examples preserved of the sternal ribs which connect the dorsal ribs with the sternum. Six pairs have been counted. A more interesting feature in the ribs consists in the presence behind the sternum which is shorter than the corresponding bone in most birds of median sternal ribs. They are slender V-shaped bones in the middle of the abdomen which overlap the ends of the dorsal ribs like the similar sternal bones of reptiles. Such structures are unknown among birds and mammals. There is no trace in the dorsal ribs of the claw-like process which extends laterally from rib to rib as a marked feature in many birds. Its presence or absence may not be important because it is represented by fibrocartilage in the ribs of crocodiles and may be a small cartilage near the head of the rib in serpents, and is only ossified in some ribs of the New Zealand reptile, Hatteria, so that it might have been present in a fossil animal without being ossified and preserved. Although the structure is associated with birds, it is possibly also represented by the great bony plates which cover the ribs in colonions and combine to form the shield which covers the turtle's back. The structure is as characteristic of reptiles as of birds, but is not necessarily associated with either. There are two remarkable modifications of the early dorsal vertebrae in some of the Cretaceous pterodactyls. First in the genus ornithodesmus from the wheeled, the early dorsal vertebrae are blended together into a continuous mass, like that which is found in the corresponding region of the living frigate bird, only more consolidated, and similar to that consolidated structure found behind the dorsal vertebrae, known as the sacrum, made by the blending of the vertebrae into a solid mass which supports the hip bones. Secondly, in some of the Cretaceous genera of pterodactyls of Europe and America, the vertebrae in the front part of the back are similarly blended, but their union is less complete. And in genera ornithocaris and ornithostoma, the former chiefly English, the latter chiefly American, the sides of the neural spines are flattened to form an oval, articular surface on each side, which gives attachment to the flattened ends of their shoulder blade bones, named the scapulae. This condition is found in no other animals. Three vertebrae appear to have their neural arches thus united together. The structure so formed may be named the notarium to distinguish it from the sacrum. Sacrum. For some mysterious reason, the part of the backbone which lies between the bones of the hips and supports them is termed the sacrum. Among living reptiles, the number of vertebrae in this region is usually two, as in lizards and crocodiles. There are other groups of fossil reptiles in which the number of sacral vertebrae is, in some cases, less, and in other cases, more. There is perhaps no group in which the sacrum makes a nearer approach to that of birds than is found among these pterodactyls, although there are more sacral vertebrae in some dinosaurs. In birds, the sacral vertebrae number from five to 22. In bats, the number is from five to six. In some solenhofen species, such as pterodactyls dubious and P. cocci and P. grandapelvis, the number is usually five or six. The vertebrae are completely blended. The pneumatic foramina in the sacrum, so far as they have been observed, are on the undersides of the transverse processes. While in the corresponding notarial structure in the shoulder girdle, the foramina are in front of the transverse processes. Almost any placental mammal in which the vertebrae of the sacral region are enclosed together has a similar sacrum, which differs from that of birds in the more complete individuality of the constituent bones remaining evident. The transverse processes in front of the sacrum are wider than in its hinder part, so that the pelvic bones which are attached to it converge as they extend backward as among mammals. The bodies of the vertebrae forming the sacrum are similar in length to those of the back. Each transverse process is given off opposite the body of its own vertebra, but from a lower lateral position than in the region of the back in which the vertebrae are free. The hip bones are closely united with the sacrum by bony union and rarely appear to come away from the sacral vertebrae as among mammals and reptiles, though this happens with the lius pterodactyls. In the Stonesfield slate and Solenhofen slate, the slender transverse processes from the vertebrae blend with the ilium of the hip girdle and form a series of transverse foramina on each side of the bodies of the vertebrae. In the Cambridge greensangera, the part of the ilium above the acetabulum for the articular head of the femur appears to be always broken away, so that the relation of the sacrum to the pelvis has not been observed. This character is no mark of affinity, but only shows that ossification obliterated sutures among these animals in the same way as among birds. The great difference between the sacrum of a pterodactyl and that of a bird has been rendered intelligible by the excellent discussion of the sacral region in birds made by Professor Huxley. He showed that it is only the middle part of the sacrum of a chicken which corresponds to the true sacrum of a reptile and comprises the five shortest of the vertebrae, while the fore in front correspond to those of the lower part of the back which either bear no ribs or very short ribs and are known as the lumbar region in mammals, so that the lower part of the back becomes blended with the sacrum and thus reduces the number of dorsal vertebrae. Similarly the five vertebrae which follow the true sacral vertebrae are originally part of the tail and have been blended with the other vertebrae in front in consequence of the extension along them of the bird's hip bones. This interpretation helps to account for the great length of the sacrum in many birds and also explains in part the singular shortness of the tail in existing birds. The ornithosaur sacrum has neither the lumbar nor the coddle portions of the sacrum of a bird. The tail. The tail is perhaps the least important part of the skeleton since it varies in character and length in different genera. The short tails seen in typical pterodactyls include as few as ten vertebrae in pterodactyls grandapelvis and pea cocci and as many as fifteen vertebrae in pterodactyls lingerostris. The tails are more like those of mammals than existing birds in which there are usually from six to ten vertebrae terminating in the plowshare bone. But just as some fossil birds like the archaeopteryx have about twenty long and slender vertebrae in the tail, so in the pterodactyl ramphorincus this region becomes greatly extended and includes from thirty eight to forty vertebrae. In dimorphodon the tail vertebrae are slightly fewer. The earliest are very short and then they become elongated to two or three times the length of the early tail vertebrae and finally shorten again towards the extremity of the tail where the bones are very slender. In all long-tailed ornithosaurians the vertebrae are supported and bordered by slender ossified ligaments which extend like threads down the tail just as they do in rats and many other mammals and in some lizards. Professor Marsh was able to show that the extremity of the tail in ramphorincus sometimes expands into a strong terminal coddle membrane of four-sided somewhat rhomboidal shape. He regards this membrane as having been placed vertically. It is supported by delicate processes which represent the neural spines of the vertebrae prolonged upward. They are about fifteen in number. A corresponding series of spines on the lower border, turned chevron bones, equally long, were given off from the junctions of the vertebrae on their undersides and produced downward. This vertical appendage is of some interest because its expansion is like the tail of a fish. It suggests the possibility of having been used in a similar way to the coddle fin as an organ for locomotion in water, though it is possible that it may have also formed an organ used in flight for steering in the air. The tail vertebrae from the Cambridge greensand are mostly found isolated or with not more than four joints in association. They are very like the slender type of neck vertebrae seen in long-necked pterodactyls, but are depressed and though somewhat wider are not unlike the tail vertebrae of the ramphorincus. The pneumatic foramen in them is a mere puncture. They have no transverse processes or neural spines nor indications of ribs or chevron bones. The hindermost specimens of tail vertebrae observed have the neural arch preserved to the end as among reptiles, whereas in mammals this arch becomes lost towards the end of the tail. The processes by which the vertebrae are yoked together are small. There is nothing to suggest that the tail was long except the circumstance that the slender coddle vertebrae are almost as long as the stout cervical vertebrae in the same animal. No small coddle vertebrae have ever been found in the Cambridge greensand. The tail is very short, according to Professor Williston, in the toothless ornithostoma in the chalk of Kansas. The hip girdle form a basin which encloses and protects the abdominal vital organs. It consists on each side of a composite bone, the unnamed bones, asa inaminata of the older anatomists, which are each attached to the sacrum on their inner side and on the outer side give attachment to the hind limbs. As a rule, three bones enter into the borders of this cup, termed the acetabulum, in which the head of the thigh bone, named the femur, moves with a more or less rotary motion. There are a few exceptions in this division of the cup between three bones, chiefly among salamanders and certain frogs. In crocodiles, the bone below the acetabular cup is not divided into two parts. And in certain plesiosores from the Oxford clay, Muranosaurus, the actual articulation appears to be made by two bones, the ilium and the ischium. The three bones which form each side of the pelvis are known as the ilium or hip bone, sometimes termed the H-bone. Secondly, the ischium or sitz bone, being the bone by which the body is supported in a sitting position. And thirdly, the pubis, which is the bone in front of the acetabulum. The pubic bones meet in the middle line of the body on the underside of the pelvis in man, and on each side are partly separated from the ischia by a foramen, spoken of as the obturator foramen, which in pterodactyls is minute and almost invisible when it exists. There is often a fourth bony element in the pelvis. In some salamanders, a single cartilage is directed forward and forked in front. According to Professor Huxley, something of this kind is seen in the dog. The pair of bones which extend forward in front of the pelvis in crocodiles may be of the same kind, in which case they should be called pre-pubic bones. But among the lower mammals, named marsupials, a pouch is developed for the protection of the young and supported by two slender bones attached to the pubes, and these bones have long been known as marsupial bones. In a still lower group of mammalia, named monotremata, which lay eggs, and in many ways approximate to reptiles and birds, stronger bones are developed on the front edge of the pubes and termed pre-pubic bones. They do not support a marsupium. Naturalists have been uncertain as to the number of bones in the pelvis of pterodactyls, because the bones blend together early in life, as in birds. Some follow the amphibian nomenclature and unite the ischium and pubis into one bone, which is then termed ischium, when the pre-pubis is termed the pubis, and regarded as removed from the acetabulum. There is no ground for this interpretation, for the sutures are clear between the three pelvic bones in the acetabulum in some specimens, like synchnoramthus fraegii from Solenhofen, and some examples of ornithocaris from the Cambridge greensand. Pterodactyls all have pre-pubic bones, which are only known in ornitho rancus and echidna among mammals, and are absent from the higher mammals and birds. They are unknown in any other existing animals and less present in crocodiles, in which ischium and pubis are always undivided. Therefore, it is interesting to examine the characters of the ornithocaurian pelvis. The acetabulum for the head of the femur is imperforate, being a simple oval basin, as in colonial reptiles and the higher mammals. It never shows the mark of the ligamentus attachment to the head of the femur, which is seen in mammals. In birds the acetabulum is perforated, as in many of the fossils named dinosaurs and in monotrimata. Secondly, the ilium is elongated and extends quite as much in front of the acetabulum as behind it. The bone is not very deep in this front process. Among existing animals, this relation of the bone is nearer to birds than to any other type, since birds alone have the ilium extended from the acetabulum in both directions. The form of the pterodactyl ilium is usually that of the embryo bird, and its slender processes compare in relative length better with those of the unhatched fowl and apterics of New Zealand than with the plate-like form in adult birds. In mammals the ilium is directed forward, and even in the cape and eater, or ecteropus, there is only an inappreciable production of the bone backward behind the acetabulum. Among reptiles the general position of the acetabulum is at the forward termination of the ilium, though the crocodile has some extension of the bone in both directions, without forming distinct anterior and posterior processes. This anterior and posterior extension of the ilium is seen in the pterodont reptiles of Russia and of South Africa, as well as in dinosaurs. Thirdly, in all pterodactyls the ilium and pubis are more or less completely blended into a sheet of bone, unbroken by perforation, though there is usually a minute vascular foramen. Or the lower border may be notched between the ilium and the pubis, as in some of the Solenhofen species, and the pubis does not reach the median line of the body. But in dimorphodon the pelvic sheet of bone is unbroken by any notch or perforation. The notch between the ilium and pubis is well marked in pterodactylus longerostris and better marked in pterodactylus dubius, synchnoramphus phrasii and ramphorincus. The fossil animals which appear to come nearest to the pterodactyls in the structure of the pelvis are pterodonts from the Permian rocks of Russia. The type known as rhopalodon has the ilium less prolonged front and back, and is much deeper than in any pterodactyl. But the acetabulum is imperforate, and the ischium and pubis are not always completely separated from each other by suture. In the pelvis referred to the theriodont deuterosaurus, there is some approximation to the pelvis of ramphorincus and of pterodactylus dubius in the depths of the division between the pubis and ischium. There are three modifications of the ornithosaurian pelvis. First, the type of ramphorincus in which the pubis and ischium are inclined somewhat backward, and in which the two pre-pubic bones are triangular, and are often united together to form a transverse bow in front of the pubic region. Secondly, there is the ordinary form of pelvis in which the pubis and ischium usually unite with each other down their length, as in dimorphodon, but sometimes, as in pterodactylus dubius, divide immediately below the acetabulum. All these types possess the paddle-shaped pre-pubic bones which are never united in the median line. Thirdly, there is the cretaceous form indicated by ornithochiris and ornithostoma in which the posterior half of the ilium is modified in a singular way, since it is more elevated towards the sacrum than the anterior half, suggesting the contour of the upper border of the ilium in a lizard. Without being reptilian, the anterior prolongation of the bone makes that impossible. It suggests the lizards. This type also possesses pre-pubic bones. They appear, according to Professor Williston, to be more like the paddle-shaped bones of pterodactylus than like the angular bones in ramphorencus. The pre-pubic bones are united in the median line, as in ramphorencus. But their median union in that genus favors the conclusion that the bones were united in the median line in all species, though they are only co-acified in these two families. This median union of the pre-pubic bones is a difference from those mammals like the ornitho rincus and echidna, which approach nearest to the reptilia. In them the pre-pubic bones have a long attachment to the front margin of the pubis, and extend their points forward without any tendency for the anterior extremities to approximate or unite. The marsupial mammals have the same character, keeping the marsupial bones completely distinct from each other at their free extremities. The only existing animals in which an approximation is found to the pre-pubic bones in pterodactyls are crocodiles, in bones which most writers term the pubic bones. This resemblance, without showing any strong affinity with the crocodilia, indicates that crocodiles have more in common with the fossil flying animals than any other group of existing reptiles, for other reptiles all want pre-pubic bones or bones in front of the pubic region. The hind limb. The hind limb is exceptionally long in proportion to the back. This is conspicuous in the skeletons of the short-tailed pterodactyls, and is also seen in dimorphodon. In Rampharencus the hind limb is relatively much shorter, so that the animal, when on all fours, may have had an appearance not unlike a bat in similar position. The limb is exceptionally short in the little tenno-draken brevirostris. The bones of the hind limb are exceptionally interesting. One remarkable feature common to all the specimens is the great elongation of the shin bones relatively to the thigh bones. The femur is sometimes little more than half the length of the tibia, and always shorter than that bone. The proportions are those of mammals and birds. Some mammals have the legs shorter than the thigh, but mammals and birds alone, among existing animals, have the proportions which characterize pterodactyls. The foot appears to have been applied to the ground, not always as in a bird, but more often in the manner of reptiles or mammals in which the digits terminate in claws. The femur. The thigh bone, on account of the small size of many of the specimens, is not always quite clear evidence as an indication of technical resemblance to other animals. The bone is always a little curved, has always a rounded articular head, and rounded distal condyles. Its most remarkable features are shown in the large well-preserved specimens from the Cambridge green sand. The rounded articular head is associated with a constricted neck to the bone, followed by a comparatively straight shaft with distal condyles, less thickened than in mammals. No bird is known, much less any reptile, with a femur like ornithochorus. Only among mammals is a similar bone known with a distinct neck, and only a few mammals have the exceptional characters of the rounded head and constricted neck, at all similar to the cretaceous pterodactyls. A few types, such as the higher apes, the hyrax, and animals especially active in the hind limb, have a femur at all resembling the pterodactyl in the pit for the obturator externus muscle behind the trochanter major, such as is seen in a small femur from ashwell. The femur varies in different genera, so as to suggest a number of mammalia rather than any particular animal for comparison. These approximations may be consequences of the ways in which the bones are used. When functional modifications of the skeleton are developed so as to produce similar forms of bones, the muscles to which they give attachment, which act upon the bones, and determine their growth, are substantially the same. In the pterodactylis longerostris, the femur corresponds in length to about 11 dorsal vertebrae. The end next, the shin bone, is less expanded than is usual among mammals, and rather suggests an approach to the condition in crocodiles in the moderate thickness and breadth of the articular end, and the slight development of the terminal pulley joint. One striking feature of the femur is the circumstance that the articular head, as compared with the distal end, is directed forward and very slightly inward and upward. So that allowing for the outward divergence of the pelvic bones, as they extend forward, there must have been a tendency to a knock-kneed approximation of the lower ends of the thigh bones, as in mammals and birds, rather than the outward divergence seen in reptiles. Apparently the swing of the leg and foot, as it hung on the distal end of the femur, must have tended rather to an inward than to an outward direction, so that the feet might be put down upon the same straight line. This arrangement suggests rapid movement. Tibia and fibula. In pterodactylis longerostris, the tibia is slender, more than a fifth longer than the femur. A crest is never developed at the proximal end, like that seen in the gullemot and diver and other water birds. The bone is of comparatively uniform thickness down the shaft in most of the sullenhofen specimens, as in most birds. At the distal end the shin bone commonly has a rounded articular termination, like that seen in birds. This is conspicuous in the pterodactylis grandis. In other specimens the tarsal bones, which form this pulley, remain distinct from the tibia, and the upper row of these bones appears to consist of two bones, like those which in many dinosaurs combine to form the pulley-like end of the tibia, which represents the bird's drumstick bone. They correspond with the ankle bones in man, named astragalus and oscalces. Complete English specimens of tibia and fibula are found in the genus dimorphodon from the lyus, in which the terminal pulley of the distal end has some expansion, and is placed forward towards the front of the tibia, as in some birds. The rounded surface of the pulley is rather better marked than in birds. The proximal end of the shaft is relatively stout, and is modified by the well-developed fibula, which is a short external splint bone limited to the upper half of the tibia, as in birds, but contributing with it to form the articular surface for the support of the lower end of the femur, taking a larger share in that work than in birds. Frequently there is no trace of the fibula visible in sullenholfen specimens as preserved, or it is extremely slender and bird-like, as in pterodactylis longerostris. In ramphorincus it appears to extend the entire length of the tibia, as in dinosaurs. In the specimens from the Cambridge greensand, there is indication of a small proximal crest to the tibia with a slight ridge, but no evidence that this is due to a separate ossification. The patella, or kneecap, is not recognized in any fossil of the group. There is no indication of a fibula in the specimens thus far known from the chalk rocks, either of Kansas in America or in England. The region of the tarsus varies from the circumstance that in many specimens the tibia terminates downward in a rounded pulley, like the drumstick of a bird. While in other specimens this union of the proximal row of the tarsal bones with the tibia does not take place, and then there are two rows of separate tarsal bones, usually with two bones in each row. When the upper row is united with the tibia, the lower row remains distinct from the metatarsus, though no one has examined these separate tarsal bones so as to define them. The foot. The foot sometimes has four toes and sometimes five. There are four somewhat elongated slender metatarsal bones which are separate from each other and never blended together, as in birds. There has been a suspicion that the metatarsal bones were separate in the young archaeopteryx. In the young of many birds the row of tarsal bones at the proximal end of the metatarsus comes away, and there is a partial division between the metatarsal bones, though they remain united in the middle. And among penguins in which the foot bones are applied to the ground instead of being carried in the erect position of ordinary birds, there is always a partial separation between the metatarsal bones, though they become blended together. The pterodactyl is therefore different from birds in preserving the bones distinct through life, and this character is more like reptiles than mammals. The individual bones are not like those of dinosaurs and diverge and rampharencus as though the animals were webfooted. There is commonly a rudimentary fifth metatarsal. It is sometimes only a claw-shaped appendage like that seen in the crocodile. It is sometimes a short bone, completely formed and carrying two phalanges in sullenhofen specimens, though no trace of these phalanges is seen in the large toothless pterodactyls from the Cretaceous rocks of North America. In the pterodactyls lingerostris, the number of foot bones on the ordinary digits is two, three, four, five, as in lizards. But the short fifth metatarsal has only two toe bones. In dimorphodon, the fifth digit was bent upward and supported a membrane for flight. There are slight variations in the number of foot bones. In the species pterodactyls scolopasiceps, the number of bones in the toes follows the formula two, three, three, four. In pterodactyls micronics, the number is two, three, three, three. The terminal claws are much less developed than is usual with birds. And there is a difference from bats in the unequal length of the digits. Taken as a whole, the foot is perhaps more reptilian than avian, and in some genera is crocodilian. The foot is the light foot of an active animal. Von Meyer thought that the hind legs were too slender to enable the animal to walk on land. And Professor Williston, of the University of Kansas, remarks that the rudimentary claws and weak toes indicate that the animal could not have used the feet effectively for grasping, while the exceedingly free movement of the femur indicates great freedom of movement of the hind legs. And he concludes that the function of the legs was chiefly for guidance in flight through their control over the movements, and expresses his belief that the animal could not have stood upon the ground with its feet. There may be evidence to sustain other views. If the limb bones are reconstructed, they form limbs not wanting in elegance or length. If it is true, as Professor Williston suggests, that the weight of his largest animals with the head three feet long and a stretch of wing of eighteen or nineteen feet did not exceed twenty pounds, there can be no objection to regarding these animals as quadrupeds or even as bipeds on the ground of the limbs lacking the strength necessary to support the body. The slender toes of many birds and even the two toes of the ostrich may be thought to give less adequate support for those animals than the metatarsals and digits of pterodactyls.