  ILLUSTRATIVE OF THE MODIFICATIONS OF THE ORNITHOSAURIA (OR PTERODACTYLES) IN THE
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 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 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 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. 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 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 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 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 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, 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 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.
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 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 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 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 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 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 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 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 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 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. The pterodactyle wrist is made up of three bones, arranged as a proximal carpal, a distal carpal, and a lateral carpal. Two of them are figured by Professor Owen, who regarded the distal carpal of this description as the scapho-cuneiform; while A very imperfect example of the proximal carpal is named the unciform: neither of these determinations, the reverse of those which follow, were given as more than probable guesses. I. Proximal Carpal. No. 10 shows the proximal surface well; portions of it are seen in Nos. 4, 5, 6, 8, 9, 11, and 12. The distal surface is best exhibited in No. 1; portions of it are shown in Nos. 2, 3, 5, 7, 8. No. 13 is an impression taken from the proximal surface of a distal carpal to show its correspondence with distal surface of the proximal carpal. The bone is proximally of an irregular oblong form, being five sided, and much broader towards the inner end than towards the outer end. The two ends are sub-parallel, and rather obliquely connected on one side by a nearly straight border more than twice as long as the shorter end. The other limits of the sub-parallel ends are connected by two concave borders meeting in a well rounded convexity, which is near to the broader inner end. The proximal surface of the bone is flattened, and may be divided into a sub-rhomboid space, adjacent to the shorter of the sub-parallel ends, which is moderately concave in the long axis of the bone and slightly convex transversely, and an oblong space adjacent to the longer of the two ends. This is separated from the sub-rhomboid This carpal is moderately compressed from the proximal to the distal side, except towards the shorter end of the bone, being there prolonged distally into a wedge-shaped process, showing at its termination marks of a powerful muscular attachment. The outer lateral surface is of variable antero-posterior extent. The distal articular surface is placed entirely toward the narrow end of the bone, leaving at the proximal end a large smooth rhomboid unarticular area, of which every side is a little concave: it connects obliquely the proximal with the distal articular surfaces. The distal articular area is divided by a diagonal ridge into a long oblong area of which the inner and outer sides are sub-parallel and the ends rounded: it is slightly concave in length as well as transversely, and is slightly twisted like the flukes of a screw. Adjacent to this region laterally is the other and sub-triangular part of the articulation. The broad end of the triangle is toward the broad end of the bone; it is concave in length and flattened transversely. The two parts of the articulation II. Distal Carpal. The tablets of this bone comprise 22 specimens. Nos. 2, 3, 4, 5, 6, 8, 9, 10, 15, 16, 19 and 22 are so mounted as to exhibit the proximal surface. Nos. 7, 11, 12, 13, 14, 15, 16, 20 and 21 show the distal surface of the bone. No. 17 is a cast from the distal surface of a proximal carpal for comparison with the proximal surface of the distal carpal. No. 16 is a cast from the proximal end of the wing-metacarpal for comparison with the distal surface of the distal carpal. No. 20 is a distal carpal of unusual type, 19 is a cast from its proximal surface, and 21 is a cast from the distal surface of the same specimen. The proximal aspect of this bone is rather narrower than the distal aspect; each is sub-triangular in outline, the sides being convexly curved. In the long axis from the apex on the inside to the short outer The lateral aspects of the bone are at right angles to the proximal and distal surfaces. They are smooth, a little concave in antero-posterior extent, and convex in the opposite direction. That one on to which the marginal articular surface impinges is except for that surface sub-quadrate in outline; the opposite side has a slightly crescentic form, the flattened outline being distal. They show several small foramina. The distal aspect of the bone is comparatively flat. The distal surface consists of a smooth unarticular part adjacent to the apex, rather smaller than the corresponding area on the proximal aspect of the bone. Between this part and the sub-crescentic articular surface, which occupies the remainder of the distal area, is a large circular pit, furthest removed from the side of the bone which forms the sub-apical marginal articulation. The pit on the apical side shows several small foramina; on the outer side of the bone the roughened articular surface extends down the pit side. The articulation is flattened from side to side of the bone. Its outer margin is slightly prominent, and the margin of the pit is slightly convex and prominent, so that the intervening articular surface in the direction between these limits is concave. It is commonly divided into two parts by a median band limiting a depressed half, which is in a slightly different plane from the other half of the articulation. Where the depressed part terminates towards the marginal articulation, which does not extend so far distally, there is between the two a small step-like roughened articular portion. The large crescentic articulation described gave attachment to the wing-metacarpal bone; if there was a second metacarpal terminating in a claw, it must have been attached to the small articulation last referred to. In No. 20 the pit is extremely small, the impressed part of the articulation is small and deeply sunk, while the apicular articulation is widened and shortened so as to make the outline of the bone quadrate. III. Lateral Carpal. The tablet exhibits eight examples of a bone which at its distal end is attached to the marginal apicular articulation of the distal carpal, thence extending proximally, and terminating in an articular facet for the third bone of the fore-arm, so as to overlap laterally both of the other carpals. The bone is compressed, is three times as wide as thick, and in outline sub-quadrate with a distal talon. On the inner side it is flat, and on the outer side above the talon it is concave vertically and convex transversely in such way that the side of the bone to which the distal articulation is adjacent is thicker than the other side, and sometimes bent at a sharp angle. The talon on the inner aspect of the bone is The Carpus of the Cambridge Ornithosaurians at first sight is not easily compared with that of Birds; Birds having but one bone between the radius and the metacarpus. But that one bone in the Ostrich, for instance, is not unlike in form to the proximal carpal of Pterodactyle; while the proximal end of the metacarpus presents so close an analogy with the distal carpal of the Pterodactyle, that even were it not easily demonstrated that the bone in Birds commonly called the metacarpus is a carpo-metacarpus In Birds the rudimentary thumb (or second finger, according to Owen) has no connection with the carpus. In the Penguin, Aptenodytes Patagonica, it has disappeared altogether, and there then remain two fingers of which the outer one (seen from the front as we have placed our animal) is the larger, and has the greatest number of phalanges, precisely as in Ornithosaurians. Moreover the wing-metacarpal, in the Penguin especially, is seen to unite with the carpus directly under the radius, as is the case with the Notwithstanding the opinions of eminent German philosophers to the contrary no reptile has a carpus comparable to that of the Pterodactyle. If some of them have two rows of bones and a pisiform bone, so have mammals, and the mammalian arrangement is not more like the Ornithosauria than is that in Reptiles.
METACARPAL BONE. Pl. 6. The illustrations of this bone comprise 31 specimens. Nos. 1 to 15 are examples of the proximal end, and Nos. 16 to 31 show the distal trochlear end of the bone. No. 1, which is nearly entire, gives the form and proportions of the wing-metacarpal in one species, but a knowledge of its variableness in German forms would guard against an assumption that all the other Greensand species were to be restored on the plan of this example. It is 35/8 inches long, to which three-eighths of an inch may be added for the distal articulation, making the length up to 4 inches. The proximal end is not well preserved, but in its wide measurement is 5/8ths of an inch; the distal end in the same measurement is about 3/8ths of an inch. A large example from the Chalk, in the Museum of C. Moore Esq. of Bath, shows the bone more attenuated distally. No. 1 is compressed so as to be oblong in section at the proximal end, and ovate in the middle of the shaft, which is slightly smaller than the distal end. One of the lateral outlines is straight; the other is concave. The bone is straight. In No. 30 the shaft where thickest measures less than 1/4 of an inch, becoming nearly circular in section. The shaft of No. 31 measures nearly an inch in width at its distal end, rather more than half an inch in thickness. No. 10 is 11/2 inch wide at the proximal end and 7/8ths of an inch thick. No. 9 would not have measured less when perfect than 21/2 inches over the proximal end, so that if it had the The Proximal End. The proximal end has never been figured. Prof. Owen's figure pl. IV. fig, 4-5, First Supt. Cret. Rep. is probably part of a jaw, and not the wing-metacarpal. The articular surface is oblong with one corner rounded off so that the adjacent long and short sides become confluent on the exterior surface of the bone. In the middle of the flat inside margin and extending proximally is a semi-cylindrical process, which is prolonged a short distance down the side of the bone as an elevated ridge. On the flattened articular end this process is bordered by a semicircular furrow which extends half-way across the bone, outside of which is a slightly convex semicircular band which extends to the outer margin of the bone, except towards the short side opposite to that one which rounds into the outer side, where there appears to be a narrow unarticular area. On the inside of the bone where the two ends of the semicircular proximal furrow terminate are two deep grooves which extend a short distance distally; they are both limited by inward extensions of the short sides of the bone, that crest being most developed in height and length which is toward the flattened short side. The outline which these modifications give to the inner side of the proximal surface is intermediate in form between the letters S and . The Distal End. The distal end has been figured by Prof. Owen in the British Fossil Mammals, p. 545; in Dixon's Geology of Sussex, Pl. XXIX. fig. 12; Cret. Reptiles, Pl. XXXII. figs. 4 and 5, First Supt. Pl. IV, fig. 9-11, and other places, and fully described. It closely resembles the distal end of a bird's tibia; and consists of a pulley-shaped end set obliquely on to the compressed shaft, which just above the junction is reniform in section, owing to the development of a median rounded ridge on the same inner side of the bone which bears the median ridge at the proximal end, while on the opposite side there is a corresponding median depression which does not extend far proximally. In this depression is Limited to the base, between the two outer ridges of the pulley, is a short median ridge slightly developed; so as to flatten the middle of the concavity between the ridges, and divide it into two grooves. The degree to which the middle ridge is developed varies in different species. In No. 30, the smallest pterodactyle, remarkable for a long wing-metacarpal bone, it is not to be detected. The exterior sides of the trochlear articulation are broad, flattened, and a little concave. There is some variation in the way in which the shaft is set on the trochlear end. It being often in the middle, but not unfrequently inclined more to one side than to the other. The metacarpus finds no close parallel among living animals. The thread-like metacarpal bones suggest the condition of the hind-foot in the Kangaroo. The predominant metacarpal suggests the ruminants. But the nearest approximation is found among birds where the bone for the middle finger is large and the bone for the third finger is slender. This may be observed (among other examples) in the Penguin and the Swan. But here the parallel ends. The proximal end in Birds, we have already seen to be hidden by the anchylosed distal row of the carpus, and the distal end though often convex from side to side never presents the trochlear joint of
FIRST PHALANGE. Pl. 7. No perfect specimen of the first phalange has been found in the Cambridge Greensand. Ten bones are mounted to illustrate it, all of them less perfect than others in the series of associated bones. No. 1 shows the heel of the proximal end; Nos. 9 and 10 are portions of the proximal articulation from which the epiphysis which forms the articular heel-part seen in No. 1 has come away. Nos. 2 to 8 are the distal articular ends of first phalanges. It is improbable that any of them belong to the second phalange, since they agree in form, and show muscular attachments which correspond. Prof. Owen has figured the shaft of a fine example of this bone in Dixon's Geology of Sussex, Pl. XXXIX. fig. 11. A good proximal end is shown in Pl. XXXII. fig. 2, of Prof. Owen's monograph of the Cretaceous Reptilia, but the figure appears to have been previously given in Pl. XXIV. fig. 2 of the same monograph. By far the grandest specimens are drawn in Pl. XXX. Prof. Owen names these wing bones. In the "Literature of English Pterodactyles" the loss of the proximal epiphysis from the specimen represented in Prof Owen's fig. 1 and 2 led me to interpret the bone as an ulna. Figs. 1 to 4 represent the proximal ends and greater portions of the shafts of first phalanges. The lower bone in fig. 5 is neither radius nor ulna, as stated in the text of the Cretaceous Reptilia, but the shaft and distal end of a first phalange; the upper bone being the second phalange. The Proximal End. The straight shaft throughout its length is triangular in section. One side of the bone is gently convex; this may be named for convenience the outside. The two parts which make up the other When the proximal epiphysis forming the heel comes away, it leaves a large sub-circular pit with a depressed narrow border. Distal End. On nearing the distal end, the angle of the inner side of the shaft becomes more depressed; and the articulation becomes an elongated oval, slightly convex transversely and convex in length so as to extend distally in a curve in such way that the articulation looks downward and outward from an aspect of the bone exactly opposite to the aspect from which the proximal articulation looks upward and inward. Hence the two articular surfaces are sub-parallel; but the distal one at its distal termination is bent inward, so as to make the adjacent lateral outline of the bone concave on the inside at its termination. The articulation does not cover the most proximal part of the distal surface.
SECOND PHALANGE. Pl. 7. On this tablet are mounted 14 specimens. Nos. 1 to 9 are examples of the proximal end of the second phalange. If there The proximal end of the shaft has the outer side flattened, rarely concave, commonly slightly convex; the inner side being much more inflated, and not dissimilar in form to the inner side of the first phalange. Proximally the bone widens and one lateral outline extends outward in a curve, on the inner side of which, under the proximal articulation, is placed the pneumatic foramen. The elongated oval articular surface is concave from side to side and concave in length; it does not extend in length so far as the straight side outline, exterior to it being a crescentic flattened or convex area. The distal end attenuates more rapidly in some specimens than others, and appears in Nos. 11, 12, and 14 eventually to become cylindrical; but none of the specimens show its distal termination. The phalanges of the wing-finger attain a grand development in length which is not paralleled in Birds, nor surpassed in Bats. In the Ostrich there are three phalanges in the wing-finger, while in Ornithopterus there are two joints, and in other German Pterodactyles four joints. The terminal joint in the Ostrich is a claw, but in Pterodactyle the terminal joint appears to be unarmed as in ordinary birds. The form of the bones in being compressed from side to side is more bird-like than bat-like. But the claws in their compression from side to side are more like the bat than the bird.
Sub-cylindrical bones, apparently elongated, and a little compressed obliquely, terminating distally in a slightly expanded trochlear articulation. Some of them show on one side marks of an osseous adhesion: this has led to their being regarded as
CLAW PHALANGE. Pl. 8. These three sub-triangular bones, which supported the claws, are much compressed from side to side, and consequently deep. The superior outline is convex from front to back and rounded from side to side. The inferior outline is concave from front to back, sometimes narrower, sometimes broader than the upper part of the bone, while the inferior aspect is always more flattened than the superior aspect. On each side on the lower half of the bone is a deep groove. The articular end is divided into an upper articular part, which extends as far down as the lateral groove and a lower non-articular part with ligament markings. The articulation is concave from above downward, and is divided into two lateral parts by a mesial vertical ridge. The articular end is about half as deep as the bone is long.
Nine specimens are mounted in illustration of the pelvic girdle: Nos. 1, 3, 4, 5 and 6 show the acetabular or femoral aspects. The right os innominatum is exemplified by Nos. 1, 4 and 5; the left by Nos. 3 and 6. No. 2 shows the sacral aspect of a left ischium, and its attachments with the pubis and ilium. No. 8 is the sacral aspect of a left os pubis. No. 9 is the femoral aspect of a right OS pubis. None of the specimens are sufficiently complete The ossa innominata have been determined as right and left on the supposition that the pelvis of the Dimorphodon is in situ, and from the general correspondence of the form of the constituent elements with elements of the pelvis in the lower mammals, reptiles, and birds. Each os innominatum shows a hemispherical acetabulum which is slightly elongated in antero-posterior extent In the Dimorphodon the bone which is superior to the cup, that is to say, which extends dorsally along the sacral vertebrÆ is prolonged anteriorly as a strong narrow straight style, the base of which is seen in the parts marked Ilium in Nos. 1 and 6. A more perfect example may be studied in a pelvis from the Cambridge Greensand preserved in the collection of the Geological survey. Posterior to the acetabulum a similar but stronger bony style extends for more than the length of the acetabulum, curving slightly downward at its posterior part. The dorsal outline of this portion of the bone is slightly concave. The posterior horn like the anterior horn forms part of the ilium which constitutes the upper half of the acetabular cup. The os innominatum contracts in antero-posterior extent below the acetabulum, and immediately widens again in a thin concave bony expansion. The anterior or pubic outline is comparatively straight, and at right angles with the ilium; the posterior or ischiac outline is deeply cupped where the ischium unites with the ilium, and becoming straight extends backward at a considerable angle. The ischium contributes less to the pelvic cup than either the ilium or pubis; it is flat in front and convex on the visceral side, rounding into the narrow flattened posterior side. The pubis is separated from the ischium by a suture extending vertically through the obturator foramen. The obturator foramen [seen in No. 9] is small and oval, less than half the diameter of the acetabulum, situated below its ventral border. It passes obliquely downward and a little forward, and its opening makes the exterior aspect of the pubis concave; the visceral aspect of the pubis is convex from side to Moreover specimens Nos. 3 and 4 show on the anterior pubic border, about the base of the acetabulum, a slight pit or roughness to which something has been attached, and in the original specimen of Dimorphodon associated with the pelvis are two triangular bones which recall something of the form of the prepubic bones of Echidna. Most German Pterodactyles show on the OS pubis an enormous prepubic bone. In Iguana the pubis forms at its anterior border, a sharp angular process. In Chelydra the process is long and narrower, and arises from the middle of the border. In Echidna this prepubic process has become a distinct prepubic bone and is more elongated. Unlike the marsupial bones it is attached to the pubis by a wide base. The anterior pubic roughness of Cambridge specimens, and the loose bones of the Dimorphodon, &c. indicate the existence of structures in the Ornithosauria homologous with the prepubic bones of the Ornithodelphia. So far as it is comparable with living animals, the ilium is altogether avian, differing in being narrower; and the pubis and ischium are mammalian. The upper anterior corner is the most elevated part of the acetabular border, as in the great Auk and some birds of vertical position of body, and many mammals.
FEMUR. Pl. 8. Twenty-six specimens are mounted to illustrate the Femur. 10 are proximal ends; 16 distal ends. But in the series illustrative of species is an entire specimen of a right Femur 4 inches long. Fragments Nos. 3 and 12 show proximal and distal ends twice as large, but most of the examples are about the size of the entire femur. It is a straight sub-cylindrical bone, flattened in front, a little compressed from front to back distally, and (in one type) compressed proximally from side to side behind. The distal articulation has a broad shallow channel passing down from the front and imperfectly separating two condyloid parts, which extend a little backward and are divided behind. The outer condyle extends a little outward, and so gives the outer side of the bone at the distal end an oblique compressed aspect like that which prevails among birds and many mammals. Proximally the shaft contracts suddenly and is produced upward, forward, and inward as a rounded neck, as long as in the femur of any mammalian carnivore, which expands rapidly at the end to form the hemispherical ball, which articulates with the pelvic acetabulum. No. 1 shows a well-marked pit for the ligamentum teres at the back part of the ball. At the proximal end of the shaft below the neck is a large pit for the obturator muscle, and at the outer front angle a great trochanter. Proximally the bone can only be compared with the mammalian Carnivora, Quadrumana and Man; distally it is avian and mammalian. In one genus exemplified by specimens 5-10 the obturator pit is not developed. Sometimes the shaft is curved a little convexly, outward and forward.
TIBIA. Pl. 8. Eleven specimens are mounted to illustrate the tibia, of which 1 to 9 are regarded as proximal ends; and 10, 11 with less confidence are regarded as distal ends from which the distal epiphysis The bone is at the proximal end straight and sub-cylindrical, slowly enlarging proximally; convex behind, except for an elevated boss some little way below the proximal articulation for the attachment of powerful muscles. In front the shaft is a little flattened proximally, with a mesial groove dividing two prominences which are apparently homologous with the ridges below the patella in birds. The proximal articular surface truncates the shaft at right angles except at what is regarded as the outer front aspect, where it rises into a small patelloid prominence. It shows the impressions of two condyles, which correspond in form with the distal end of the Femur. Nos. 3 and 6 are regarded as left tibia; Nos. 4, 5, 7, 8, 9 as examples of right tibia. No specimen likely to be a fibula has been found. In Dimorphodon and in German Genera the fibula is Avian in form. The Crocodile offers some approximation to the Pterodactyle shape in the proximal end of the Tibia, but the Pterodactyle has Avian characters in addition. Its straightness and length, ridges on the front and patelloid prominence, are Avian.
TARSUS OR TARSO-METATARSUS. Pl. 8. This fragment, which may be the distal end of the bone corresponding to that called in birds the tarsus or tarso-metatarsus, is badly preserved. Yet so close is its resemblance in form, structure, and apposition of the constituent bones to what obtains among birds, that it may probably be identified as the tarsus; while the peculiar characteristics of Pterodactyle bones which it shows, demonstrate that it is not from a bird, but from an Ornithosaurian skeleton. The bones are of paper thinness, and consist of a strong bone behind which distally appears on the inner side to be compressed and thrown backward and flattened at the side, exactly like the inner toe in Natatorial birds. On the front of this strong support, confluent with it, and confluent together, so that This bone, if correctly determined, offers points of affinity with birds as pronounced and as important as any thing shown by the extremities, for among reptiles a welding of the (tarsal or) tarso-metatarsal bones is unknown, and here it is as absolute as in any bird, and takes a characteristic bird shape. In the Rodent Jerboa the metatarsus has much the same form as in a bird. No phalanges have been recognised.
Fifteen specimens are mounted to exemplify the structures of the Pterodactyle atlas and axis. Nos. 1, 11, and 2 have already been figured, and described by Prof Owen, the latter as a section of a cervical vertebra. The atlas centrum, a saucer-shaped disk of bone, commonly united more or less intimately with the centrum of the axis, but sometimes free. It presents in front a hemispherical cup for the basi-occipital, and is flattened or slightly convex behind. Its neural arch is seen in Nos. 2, 10, and 12; but the only specimen with the arch entire is in the museum of James Carter, Esq. The neurapophyses vary in form and size, but always are small obliquely flattened lamellar bones, which extend upward and backward to meet the neural arch of the axis, just above the neural canal, where a thin and small cross piece connects them together. The distinctive aspect of these bones is given by the neural arch of the axis, which is very much elevated, and is formed by two flattened sides, which meet in a vertical ridge above the neural canal, and look forward, outward and upward; extending laterally more and more beyond the side of the centrum, but not reaching so far back as the posterior articulation of the centrum. Each side of the neural arch at its middle part behind is produced into a thick obliquely flattened process, the under portion of which The centrum is shorter than in cervical vertebrÆ, commonly convex (No. 8) on the visceral surface; often with a slight longitudinal hypapophysial ridge (Nos. 1; 7; 12) rarely flattened (No. 10). Towards the hinder part the centrum widens, and becomes concave on the visceral surface, sending off as do the other cervicals, below the transversely elongated posterior articulation, a pair of short strong apophyses. The posterior articulation can only by a modification of the idea be said to conform to the cup-and-ball plan, for though convex from above downward and convex from side to side, the elongated transverse measurement would be three times the depth. On the under side an impressed transverse line divides the articulation from the concave part of the centrum below.
Forty-three specimens are mounted to exemplify the variations in size and characters of cervical vertebrÆ. These for the most part are specific characters; and between the axis and the first dorsal vertebra the variations in an individual were slight. [Those nearest to the back, as in birds, are widest in front, and have the highest neural arches.] The associated series show commonly The centrum is united to the neural arch as in birds, without a trace of suture; sometimes the neural arch is no wider than the centrum, sometimes it extends over the centrum on each side. Those forms with a narrow neural arch have the neural spine high, and its sides look forward as well as outward. The pneumatic foramen is oblique. An example is figured by Prof. Owen, in the memoir on Pterodactylus simus, pl. 2, fig. 4. The forms with a wide neural arch have the neural spine rising from the middle of the dorsal surface, erect and equally compressed from side to side. The pneumatic foramen is horizontal. An example is figured in Prof. Owen's memoir on Pt. simus, pl. 2, fig. 1. These two forms of cervical vertebrÆ may be regarded as typifying two genera. In both forms many characters occur in common, and as the specimens illustrative of special modifications will be described hereafter, the following description has been made to embrace the chief characteristics of these vertebrÆ in Cretaceous Ornithosaurians. The inferior aspect of the centrum is oblong (being narrower than long), or quadrate; when quadrate the additional lateral expansions are external to the pneumatic foramina, and are formed by the neural arch and zygapophyses. The centrum proper is a little wider in front than behind, and the side outlines are concave. The base of the centrum is flattened, or more or less hollow, or more or less tumid and regularly convex; in front there is often a mesial ridge, which never reaches the posterior articulation, and forms a prominent tubercle at the base of the anterior articulation. At the posterior end the outline of the centrum is concave, and mesially the bone has a hollow corresponding to the tubercle in front of the adjacent vertebra; and the part of the centrum on each side is prolonged slightly into a strong rounded or flattened tubercle below the side borders All the Cretaceous Pterodactyles have the articular surfaces of the centrum transversely oblong, as have some birds. The posterior articulation is convex from side to side, and convex from above downward, and appears to extend a little further on this neural than on the hÆmal surface; in outline it is commonly an elongated oval, but sometimes attends on the upper surface of the inferior lateral tubercles. The anterior articulation is transversely elongated, concave in both directions, and sub-triangular in outline; that is to say, the superior outline is more or less convex, and from its limits to the mesial tubercle at the base, the inferior outlines are more or less concave. The neural canal is sub-circular or ovate in outline, and quite as large as the neural canal in vertebrÆ of Dinornis of similar size. The neural arch like the centrum has commonly a depressed appearance. It always has a neural spinous process which is directed upward. In the depressed type the neural surface of the vertebra is in outline usually sub-quadrate, but concave at each side, and concave in front and behind; the four corners are the processes which support the zygapophysial facets, the surface is divided into two lateral parts by the strong neural spine. These lateral parts are from front to back flat, or slightly concave, or slightly convex; and from the neural spine outward they are always concave. The neural spine is commonly sharp in front and flattened behind. The neural arch is placed well forward, so that while a third of the neural canal remains uncovered by it behind, rarely a sixth would be uncovered in front. The anterior and posterior zygapophyses are commonly connected by a more or less rounded ridge, undefined above, but well defined below, since under its posterior part at about the middle of the side of the centrum is placed the pneumatic foramen. The anterior zygapophysial processes are separated from the anterior articular surface of the centrum by a more or less oblique The anterior zygapophyses are strong processes directed forward and outward, compressed a little from side to side; they are placed at the outer sides of the anterior articular face of the centrum, and extend in front of it. The zygapophysial facet is commonly oval and looks upward and inward and forward. The posterior zygapophyses are short and massive, but otherwise correspond closely with the anterior zygapophyses, only with all the parts reversed, and except that necessarily they are relatively to the neural canal a little higher. A sharp and well defined angular ridge, commencing at the back of the zygapophysis, is directed inward, and forward, and upward along the posterior margin of the neural arch to the top of the neural spine. The posterior aspect of the neural arch is concave from side to side, and makes a right angle with the superior lateral aspect. The part of the centrum exposed behind the neural arch is convex above from side to side. The pneumatic foramen between the centrum and the neural arch varies greatly in size; it is oval and longitudinal. The largest specimens have the centrum 21/2 inches long; in the smallest the centrum measures 5/8ths of an inch in length. In the second type of cervical vertebra the side of the centrum makes a right angle with the base, and is separated from it by a sharp angle as in struthious birds. The side of the centrum is concave, with a few small pneumatic perforations; and the side of the centrum, which is high posteriorly, rounds over the oblique ridge connecting the zygapophyses, into the oblique lateral face of the neural arch. The anterior zygapophyses are very large and the posterior zygapophyses small and placed as high as the top of the neural canal. Every region of the vertebral column displays pneumatic foramina, situated as in the vertebrÆ of birds. The large proportional size of the neck-vertebrÆ is common to some birds, and is conspicuous in many mammals, like the Llama. In most mammals where the vertebrÆ have a cup-and-ball articulation, the ball is in front, as it is in the dorsal vertebrÆ of the penguin, so that those vertebrÆ are not comparable with Pterodactyles, although on the under side of the centrum they similarly give off a mesial process below the cup, and a lateral process below the ball on each side. The neural spine in Pterodactyle is commonly more developed than is the case with long-necked birds or mammals. Reptiles such as Crocodiles and Lizards have the neural spines of the neck-vertebrÆ well developed. Birds differ from Pterodactyles in the peculiar articulation of their vertebrÆ. In both the centrum is often depressed, in both it is concave from side to side in front, and convex from side to side behind, but in birds it is also convex from above downward in front, and concave from above downward behind, while the reverse arrangement obtains in Pterodactyles. A similar condition to that of the bird is seen in the neck-vertebrÆ of the Kangaroo, of Man, and several mammals, only the vertical curves are less marked. VertebrÆ concave in front, and convex behind, and devoid of cervical ribs, are met with among the Lizards, but neither Monitor nor Iguana offer any parallel to the form of the cervical vertebrÆ of Pterodactyle, which is best matched among Marsupials and Birds. Birds commonly have more vertebrÆ in the neck than have Pterodactyles, which in that respect resemble mammals and some Lizards. Twenty specimens are mounted to exemplify pectoral and dorsal vertebrÆ. Like the cervical vertebrÆ, they include two types of form, one with the centrum flat, figured in pl. 2. fig. 20-22 of the memoir on Pterodactylus Sedgwicki, and regarded by Prof Owen as anterior dorsal; and the other form with a convex centrum, figured 24-25 of the same plate of the same memoir, regarded by Prof. Owen as posterior dorsal. Following the analogy of birds such determination is as well Nos. 1, 3, 6, 7, 8, 9, 10, 14, 15, 19 belong to the flat type. Nos. 2, 4, 5, 11, 12, 16, 17, 18 exemplify the convex type. Dorsal vertebrÆ are rare fossils; and in the associated sets of bones never more than four dorsal vertebrÆ are found, rarely more than one. No specimen of the type with a convex centrum occurs in the associated sets. The dorsal vertebrÆ with convex centra have all lost their neural arches except No. 2. The form of the centrum is half a cylinder, as long, or longer than wide, but sometimes depressed, and wider behind than in front. The exterior surface is smooth, convex from side to side, and slightly concave from front to back. The neural surface is mesially excavated. Both anterior and posterior articular surfaces are semicircular or sub-ovate, being wide from side to side. The anterior articulation is cupped, concave from the neural to the hÆmal surface, and concave from side to side. The posterior articulation is convex from the neural to the hÆmal surface, in which direction, it usually shows striations, and from side to side has a gentle convexity, sometimes so slight as to be nearly flat. The neural canal is large, ovate, and as high as is the centrum. The neural arch is strong, compressed from back to front, and placed as usual on the anterior part of the centrum. In outline it is sub-rhomboid with the sides concave. There is a strong process on each side above the neural canal for a rib, and apparently a neural spine, but all are broken. The transverse processes for the ribs are directed outward, and a little forward, flattened in front and behind, the surfaces being sub-parallel, so that in front the neural arch is concave from side to side. Behind, the neural spine is directed between the transverse processes so as to over-hang the exposed part of the superior surface of the centrum. At the points where the neural spine bends back from the transverse processes are the posterior zygapophyses, high above the neural canal, and parted from each other by an interspace as wide as the Dorsal vertebrÆ of the type with the centrum flattened closely resemble cervical vertebrÆ with the centrum flattened, differing chiefly in the less length of the centrum. Occasionally (as in No. 3) the neural arch comes away from the body of the vertebra. The centrum is very depressed, sub-quadrate, and wider than long; the base is flat, or slightly concave, with occasionally a slight longitudinal mesial ridge; the lateral outlines are concave, so that the bone is pinched in from side to side. The neural surface of the centrum is flat and parallel with the base, and, as usual, wider behind than in front, but the centrum is not there so high. The surfaces for the neural arch are flat, and extend nearly to the base of the centrum in front, so that they look upward, outward and a little forward. The articular ends are remarkable for their depressed oblong character, still preserving the anterior concavity with a small mesial process below, as in cervical vertebrÆ, and similar but smaller processes at the inferior outer angles of the posterior sub-semicylindrical convexity. The middle third of the anterior cup is made by the trapezoidal anterior end of the centrum; sometimes the sutures between it and the neural arch are well marked. The neural arch is large, commonly with a sub-circular neural canal. The neural spine is high, compressed so as to have the lateral surfaces sub-parallel and rounding into each other superiorly; and it has a less antero-posterior extent than the centrum. At its base behind it widens rapidly, and forms massive quadrate processes, extending outward and backward, which on the outside each have a flattened ovate zygapophysial facet, which also looks downward. Above the facet and separated from it by a groove is a tubercle. Between the zygapophyses behind the bone is concave from side to side; the facets are placed above the neural canal. The posterior zygapophyses are placed considerably higher than the anterior zygapophyses, and the part of the neural arch between is rather constricted from front to back. The neural arch steadily widens in front down to the base of the anterior zygapophysial processes in such way that the more or less flattened lateral surface looks outward and is gently concave from above downward. A ridge commencing at the tubercle over the posterior zygapophysial facet descends in a curve forward and downward, to form the posterior border of the anterior zygapophysial process. This is separated by a groove from the anterior articular surface, and anterior part of the base of the centrum, and has the aspect of a compressed part of the neural arch, extending obliquely downward, and forward, over and beyond the articular surface of the centrum. The anterior zygapophysial facets are oblong, narrow from side to side, and long from front to back; they are directed forward and a little outward, and are flattened, make nearly a right angle behind with the front of the neural arch, and look upward and inward. They are sometimes placed as high as the top of the neural canal, but are commonly lower. Around the neural canal the bone is conically impressed. Minute pneumatic foramina are in the usual position, between the centrum and the neural arch; and sometimes others behind the anterior zygapophysial process. The largest specimen known has the centrum nearly an inch and a half long. The dorsal vertebrÆ in Cambridge specimens would appear to make a nearer approximation in number to birds than to Mammals or Lizards or Crocodiles, though Chelonians have few vertebrÆ in the back. Among Reptiles the form of the vertebra makes some approach to that of the Monitor, Chameleon and Scink. In most Mammals the dorsal vertebrÆ have the centrum convex, though in the lumbar region its visceral surface often becomes flattened. But though very unlike there is a nearer resemblance to the lower dorsal vertebrÆ of a Struthious bird.
Seven specimens are mounted to exemplify the ordinary structures of the Ornithosaurian sacrum. Nos. 1 and 2 have the centrum convex, exactly as in the dorsal vertebrÆ of the convex type. Nos. 3-7 have the centrum flattened, following in general features the plan of the dorsal vertebrÆ with flat centra. No. 1 is a vertebra from a sacrum, where perfect anchylosis had not been induced; it has the neural arch well preserved, and shows the sharp suture which united it to the preceding vertebra. No. 2 shows two entire vertebrÆ and part of a third, which have lost the neural arches but have the centra perfectly anchylosed together. The middle vertebra measures 5/8 of an inch in length, and at the suture from side to side measures more. The surface is smooth, regularly convex from side to side, and gently concave from back to front. The last vertebra shows the articular vertebral surface; it is convex in both directions, and oblique, so that a large part looks upward. The anterior of the three vertebrÆ is pinched in at the lower part of the sides of the centrum. No. 1 shows that the neural surface of the centrum is deeply excavated, making the neural canal an elongated upright oval. Above the centrum, which forms only the middle third of the articular surface, the neural arch expands on each side into a wedge-shaped transverse process, the lower surfaces are flattened, and continuous with the centrum, while the upper surfaces are flat and horizontal as in birds and Dinosaurs, and form the platform from which arises the massive neural spine. In front the transverse wedge is flattened and compressed, so as to look forward and outward, and in the middle shows a large ovate pneumatic foramen. Behind, the wedge is compressed so as to look backward and downward. The neural spine is massive and forms rather more than half the height of the vertebra. It is flattened with a ridge rising near its base in front and ascending in a concave curve obliquely backward and upward. The anterior parts approximate a little in front, while the small parts posterior to the ridge approximate There is a notch on each side in front at the base of the neural spine, and another above the central articulation. The neural spines appear to have been united by suture. It may be instructive to compare the neural spine just described with the specimens J. c. 10. Of the second type or genus No. 4 to 7 all show the anterior cup for the last lumbar vertebra. No. 3, 5 and 6 all show two entire vertebrÆ and part of a third preserved, but no specimen shows the posterior termination of the sacrum. No. 7 has the articular face of the centrum very broad, and greatly depressed. In No. 6 it is ovate and has the neural arch preserved; above a semicircular neural canal it sends out on each side a short horn-like zygapophysial process. No. 4 is remarkable for the small size of the circular neural canal, the centrum when entire measuring an inch from side to side, while the neural canal only measures 5/16 of an inch. No. 5 is figured by Prof. Owen. No. 4-6 appear to have given off transverse processes from the sides of the centra. No. 7 appears to widen into transverse processes at the point of suture between the centra. In No. 3 the base of the sacrum is flattened, and its sides pinched in, and concave in outline from back to front. In this hollow are small pneumatic foramina, and between the hollows the vertebrÆ widen in the line of the suture so as to send out strong short transverse processes or tubercles. Above the hollows are given out the strong horizontal quadrate pyramidal transverse processes. All their sides are flattened or a little concave, and the under side displays a large ovate pneumatic foramen. Each of the four angles of the transverse process gives off a ridge. The lower ones descend obliquely to the anterior and posterior intersutural tubercles. The upper two ascend obliquely, in front and behind, and form rounded ridges on the neural spine. The neural spine is flattened, moderately compressed from side to side, and cupped a little over each transverse process. In front the neural spine is flattened transversely and perpendicular; the transverse processes are also flattened and a little in advance of the neural spine. The sacrum in its general aspect is Mammalian. In the Bird
Thirteen specimens are mounted to exemplify the osteology of caudal vertebrÆ. No. 7 has been figured by Prof. Owen in the memoir on Pterodactylus simus, pl. 2 fig. 13-16. The centrum of the largest specimens measures one inch and a quarter long, and the vertebra is half an inch wide from side to side in the middle. The smallest specimen No. 13 has the centrum 3/4 of an inch long. The vertebrÆ vary in proportions, some being much more slender than others. They present a close approximation in form to the first type of cervical vertebrÆ, differing chiefly in being more elongated. They are elongated bones constricted in the middle, so that the outlines of the sides seen from above or below are gently concave; the outline of the anterior end is sub-rhomboid, the outline of the posterior end is sub-pentagonal, as would be a transverse section of the vertebra. The long outlines of the base of the centrum and of the top of the neural arch are sub-parallel. The two sides of the upper surface of the neural arch are smooth, flattened, a little concave from back to front; they are inclined to each other pent-house wise at about a right angle, and are separated throughout their length by a narrow slightly elevated neural spine. Behind, the neural arch is truncated transversely so as to expose the posterior neural surface of the centrum, which is convex from side to side. The outermost lateral angles of the neural arch are the posterior zygapophysial processes, short and strong above the centrum, with a tubercle on the upper surface, and showing the sub-circular zygapophysial facets behind; they look backward and downward, and The inferior surface of the centrum is separated from the sides by two ridges parallel to the lateral concave outlines of the neural arch; they extend from sides of the front, more or less well marked, to the tubercular processes at the base of the sides of the centrum behind. The dice-box shaped area of the centrum so inscribed is usually concave from front to back, and concave from side to side behind, and convex from side to side in the middle; this convexity is only broken in front by the development of the slight mesial hypapophysial ridge. The sides are narrow, flattened, look downward and outward, are a little concave from front to back, round into the centrum and into the neural arch, and show at about the middle a small pneumatic foramen, which is variable in size, but largest in No. 8, and sometimes a mere puncture. The caudal vertebrÆ differ in many ways from other animals. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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