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those bones with the maxillaries in the gorilla and chimpanzee, to the part of the upper jaw containing the incisive teeth, on the development of which depends the prognathic or brutish character of a skull. Now the extent of the premaxillaries below the nostril is not only relatively but absolutely less in the gorilla, and consequently the profile of the skull is less convex at this part, or less 'prognathic,' than in the chimpanzee. Notwithstanding the degree in which the skull of the gorilla surpasses in size that of the chimpanzee, especially when the two are compared on a front view, the breadth of the premaxillaries and of the four incisive teeth is the same in both. In the relative degree, therefore, in which these bones are smaller than in the chimpanzee, the gorilla, in this most important character, comes nearer to man. In the gibbons the incisors are relatively smaller than in the gorilla, but the premaxillaries bear the same proportional size, in the adult male siamang.

Next, as regards the nasal bones. In the chimpanzee, as in the orangs and gibbons, they are as flat to the face as in any of the lower Simia. In the gorilla, the median coalesced margins of the upper half of the nasal bones are produced forwards; in a slight degree it is true, but affording a most significant evidence of nearer resemblance to man. In the same degree they impress that anthropic feature upon the face of the living gorilla. In some pig-faced baboons there are ridges and prominences in the nasofacial part of the skull; but they do not really affect the question as between the gorilla and chimpanzee. All naturalists know that the semnopithèques of Borneo have long noses; but the proboscidiform appendage which gives so ludicrous a mask to those monkeys is scarcely the homologue of the human nose, and is unaccompanied by any such modification of the nose-bones as gives the true anthropoid character to the human skull, and to which only the gorilla, in the ape tribe, makes any approximation.

No orang, chimpanzee, or gibbon shews any rudiment of mastoid processes; but they are present in the gorilla, smaller indeed than in man, but unmistakeable; they are, as in man, cellular, and with a thin outer plate of bone. This fact led me to express, when in respect to the gorilla, only the skull had reached me, the following inference, viz.: 'from the nearer approach which the gorilla makes to man in comparison with the chimpanzee, or orang, - in regard to the mastoid processes, that it assumed more nearly and more habitually the upright attitude than those inferior anthro

poid apes do.' This inference has been fully borne out by the rest of the skeleton of the gorilla, subsequently acquired.

In the chimpanzee, as in the orangs, gibbons, and inferior Simia, the lower surface of the long tympanic or auditory process is more or less flat and smooth, developing in the chimpanzee only a slight tubercle, anterior to the stylohyal pit. In the gorilla the auditory process is more or less convex below, and developes a ridge, answering to the vaginal process, on the outer side of the carotid canal. The processes posterior and internal to the glenoid articular surface, are better developed, especially the internal one, in the gorilla than in the chimpanzee; the ridge which extends from the ectopterygoid along the inner border of the foramen ovale, terminates in the gorilla by an angle or process answering to that called 'styliform' or 'spinous' in man, but of which there is no trace in the chimpanzee, orang, or gibbon.

The orbits have a full oval form in the orang; they are almost circular in the chimpanzee and siamang; more nearly circular, and with a more prominent rim in the smaller gibbons; in the gorilla alone do they present the form which used to be deemed peculiar to man. There is not much physiological significance in some of the latter characters; but, on that very account, I deem them more instructive and guiding in the actual comparison. The occipital foramen is nearer the back part of the cranium, and its plane is more sloping, less horizontal, in the siamang, than in the chimpanzee and gorilla. Considering the less relative prominence of the fore part of the jaws in the siamang, as compared with the chimpanzee, the occipital character of that gibbon and of other species of Hylobates indicates well their inferior position in the quadrumanous scale.

In the greater relative size of the molars, compared with the incisors, the gorilla makes an important closer step towards man than does the chimpanzee. The molar teeth are relatively so small in the siamang, that notwithstanding the small size of the incisors, the proportion of those teeth to the molars is only the same as in the gorilla: in other gibbons (Hylobates lar), the four lower incisors occupy an extent equal to that of the first four molars, in the chimpanzee equal to that of the first three molars, in the siamang equal to that of the first two molars and rather more than half of the third, in man equal to the first two molars and half of the third: in this comparison the term molar is applied to the bicuspids.

The proportion of the ascending ramus to the length of the lower jaw tests the relative affinity of the tailless apes to man.

In a profile of the lower jaw, compare the line drawn vertically from the top of the coronoid process to the horizontal length along the alveoli. In man and the gorilla it is about 7-10ths, in the chimpanzee 6-10ths, in the siamang it is only 4-10ths. The siamang further differs in the shape and production of the angle of the jaw, and in the shape of the coronoid process, approaching the lower simiæ in both these characters. In the size of the postglenoid process, in the shape of the glenoid cavity which is almost flat, in the proportional size of the petrous bone, and in the position of the foramen caroticum, the siamang departs further from the human type and approaches nearer that of the tailed simiæ than the gorilla does, and in a marked degree.

Every legitimate deduction from a comparison of cranial characters makes the tailless Quadrumana recede from the human type in the following order,-gorilla, chimpanzee, orangs, gibbons; and the last-named in a greater and more decided degree.

Those comparisons have of late been invested with additional interest from the discoveries of remains of quadrumanous species in different members of the tertiary formations.

The first quadrumanous fossil, the discovery of which by Lieuts. Baker and Durand is recorded in the Journal of the Asiatic Society of Bengal, for November, 1836, has proved to belong, like subsequently discovered quadrumanous fossils in the Sewalik (probably miocene) tertiaries, to the Indian genus Semnopithecus. The quadrumanous fossils discovered in 1839, in the eocene deposits of Suffolk, belong to a genus (Eopithecus) having its nearest affinities with Macacus. The monkey's molar tooth from the pliocene beds of Essex is most closely allied to the Macacus sinicus. The remains of the large monkey, 4 feet in height, discovered in 1839 by Dr Lund in a limestone cavern in Brazil was shewn by its 3 3 3-3

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to belong to the platyrrhine

family now peculiar to South America. The lower jaw and teeth of the small quadrumane discovered by M. Lartet in a miocene bed of the south of France, and described by him and De Blainville, is so closely allied to the gibbons as to scarcely justify the generic separation which has been made for it under the name Pliopithecus.

Finally, a portion of a lower jaw with teeth and the shaft of a

humerus of a quadrumanous animal (Dryopithecus), equalling the size of those bones in man, have been discovered by M. Fontan, of Saint-Gaudens, in a marly bed of upper miocene age, forming the base of the plateau on which that town is built. The molar teeth present the type of grinding surface of those of the gibbons (Hylobates), and as in that genus the second true molar is larger than the first, not of equal size, as in the human subject and chimpanzee. The premolars have a greater antero-posterior extent, relatively, than in the chimpanzee; and in this respect agree more with those in the siamang. The first premolar has the outer cusp raised to double the height of that of the second; its inner lobe appears from M. Lartet's figure to be less developed than in the gorilla, certainly less than in the chimpanzee. The posterior talon of the second premolar is more developed, and consequently the fore and aft extent of the tooth is greater than in the chimpanzee; thereby the second premolar of Dryopithecus more resembles that in Hylobates, and departs further from the human type.

The canine, judging from the figures published by M. Lartet', seems to be less developed than in the male chimpanzee, gorilla, or orang. In which character the fossil, if it belonged to a male, makes a nearer approach to the human type; but it is one which many of the inferior monkeys also exhibit, and is by no means to be trusted as significant of true affinity, supposing even the sex of the fossil to be known as being male.

The shaft of the humerus, found with the jaw, is peculiarly rounded, as it is in the gibbons and sloths, and offers none of those angularities and ridges which make the same bone in the chimpanzee and orang come so much nearer in shape to the humerus of the human subject. The fore part of the jaw, as in the siamang, is more nearly vertical than in the gorilla or chimpanzee, but whether the back part of the jaw may not have departed in a greater degree from the human type than the fore part approaches it, as is the case in the siamang, the state of the fossil does not allow of determining. One significant character is, however, present,—the shape of the fore part of the coronoid process. It is slightly convex forwards, which causes the angle it forms with the alveolar border to be less open. The same character is present in the gibbons. The fore part of the lower half of the coronoid process in man is concave, as it is likewise in the gorilla and chimpanzee. I am acquainted with this interesting fossil, referred to a genus

1 Comptes Rendus de l'Académie des Sciences, Paris, Vol. XLIII.

called Dryopithecus, only by the figures published in the 43rd volume of the Comptes Rendus de l'Académie des Sciences. From these it appears that the canine, two premolars, and first and second true molars are in place. The socket of the third molar is empty, but widely open above; from which I conclude that the third molar had also cut the gum, the crown being completed, but not the fangs. If the last molar had existed as a mere germ, it would have been preserved in the substance of the jaw.

In a young siamang, with the points of the permanent canines just protruding from the socket, the crown of the last molar is complete, and on a level with the base of that of the penultimate molar, whence I infer that the last molar would have cut the gum as soon as, if not before, the crown of the canine had been completely extricated. This dental character, the conformation and relative size of the grinding teeth, especially the fore-and-aft extent of the premolars, all indicate the close affinity of the Dryopithecus with the Pliopithecus and existing gibbons; and this, the sole legitimate deduction from the maxillary and dental fossils, is corroborated by the fossil humerus, fig. 9, in the abovecited plate.

There is no law of correlation by which, from the portion of jaw with teeth of the Dryopithecus, can be deduced the shape of the nasal bones and orbits, the position and plane of the occipital foramen, the presence of mastoid and vaginal processes, or other cranial characters determinative of affinity to man; much less any ground for inferring the proportions of the upper to the lower limbs, of the humerus to the ulna, of the pollex to the manus, or the shape and development of the iliac bones. All those characters which do determine the closer resemblance and affinity of the genus Troglodytes to man, and of the genus Hylobates to the tailed monkeys, are at present unknown in respect of the Dryopithecus. A glance at fig. 5 (Gorilla), and fig. 7 (Dryopithecus), of the plate of M. Lartet's memoir, would suffice to teach their difference of bulk, the gorilla being fully one-third larger. The statement that the parts of the skeleton of the Dryopithecus as yet known, viz., the two branches of the lower jaw and the humerus, ‘are sufficient to shew that in anatomical structure, as well as stature, it came nearer to man than any quadrumanous species, living or fossil, before known to zoologists',' is without the support of any ade

1 Sir Chas. Lyell, Supplement to the Fifth Edition of a Manual of Elementary Geology, 8vo., 1859, p. 14.

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