I will, therefore, just point out some of the most wellmarked characters by which this new type is distinguished from their prototypes of the old world. First, the size of the facial angle should perhaps be mentioned, although on account of the great variety of this angle in different monkeys, it can scarcely be compared in the two races. This angle, according to Camper, contains 80° in Europeans, and in some negroes which he measured, it only contained 70°. Now, in measuring the skulls of Orangs, Lesson (Hist. Nat. Mammifères, vol. iii, p. 230) estimated it at from 60°, even as high as 64°, but Professor Owen has shewn (Zool. Trans., vol. i, p. 372) that Lesson measured only young animals; and states that the facial angle of the adult Chimpanzee is only 35°, while that of the Orang is but 30°. This difference is owing to the immense development of the jaws in the adult Orangs, which is accompanied by a corresponding amount of brutal ferocity, and savage animal propensities. In the Baboons, again, the facial angle is considerably less, and every gradation between these may occur. Among the American monkeys, on the other hand, there are none which so nearly approach man, nor any which are so distant from him in organization, as are found in the old world family. Their heads are generally round, and their muzzles short, so that the facial angle is large, and varies between small limits, being from 55° to 60°; this angle, therefore, cannot be made use of in these monkeys as a character of any importance. M. Isidore St. Hilaire, the younger, has given, in the Comptes rendus, the following general statement of measurements in certain groups :— In the second place, the general size of the American type is much smaller than that of the old world monkeys. Thus, a fine specimen of the Satyrus rufus, in the British Museum, stands exactly four feet high, and the anterior extremities measure rather more than three feet in length. The height to which the adult Orang attains is scarcely known, but that of the adult Gorilla is not a matter of doubt. Many other of the higher forms are also of considerable size, and the quadruped Baboons are of no mean proportions; but among the monkeys of the new world, the Howlers (Mycetes), which are allied to the Baboons, are perhaps the most robust, and seldom reach three feet in height. The genus Ateles contains the individuals which stand tallest, and some in the British Museum reach the height of three feet; but their very slender forms and elongated extremities which contribute to this height, offer a singular contrast to the thickset and robust forms of most of the old world monkeys. An extinct species has been discovered which must have been four feet high, but this is the largest known; and the lowest genera, Midas and Jacchus (usually called Marmozets), are not bigger than squirrels. Third. In the Quadrumana of the Old world many generic and specific differences depend upon the presence, absence or amount of development of those tubercular callosities on the buttocks, which are more or less defined in all the Gibbons, and in most of the Baboons; and on the cheek-pouches, which are so ample in all the family of Cercopithecians. Now, these two characters are unknown in America; and not a single species of New world monkey is possessed of either. Fourth. The tail, which is not unfrequently altogether absent in the Old world species, is in all the American monkeys (with the exception of two species of a genus which is thence called Brachyurus) highly developed; and this not only in its length, which is sometimes extraordinary, but also in its capabilities as a prehensile organ. For this purpose, the under part of its extremity is bare of hair, and callous; and is capable of being applied as a fifth hand with the utmost precision; which, as those which are possessed of this organ are exclusively arboreal, must be of the greatest service. The strength of the vertebral column, and of the muscles attached to it, reaches, in these monkeys, the highest degree of development, and the excess of power in this one organ results in the greater general strength of those so furnished. The extent of the callous part of the tail is in tolerably exact proportion to its powers as a prehensile organ, and is very constant in each species, occupying near one third in the Howlers, and two-fifths in the genus Brachyteles, &c. This very remarkable feature is peculiar to American monkeys, and is possessed by more than half of the whole number of species. The Fifth. They differ as to their dental formula. Quadrumana of the old world possess an array of teeth which is expressed thus 2-2 3-3 Inc. Can. Bicus. True Mol. 2-2 thus agreeing with man in the number of their teeth, but differing widely from him, and from each other, in the development of individual teeth, and dental tubercles. But the monkeys of the new world possess an additional molar tooth on each side of each jaw, which thus gives them thirty-six, instead of thirty-two teeth. In the Marmozets, however, these additional molars are wanting. The significance of such changes as these will be best understood by a reference to Prof. Owen's valuable work on Odontography. Sixth. Another remarkable point of difference between the Quadrumana of the old and new continent is, that all the former (including even the family of the Lemurs, which in many respects aberrate widely from the monkey type) possess both on the anterior and posterior extremities an opposable thumb; whereas the opposable character of the thumb is, in the latter, confined to the posterior extremities. This is undoubtedly a character of importance, but by no means such as to justify an attempt at classification upon that character alone. Such an attempt was made about thirty years ago, by Mr. Ogilby, but, as might have been expected, it has never been adopted; and his plan, which may be found in the Proceedings of the Zoological Society, 1836, was to arrange all the mammalia which were possessed of opposable thumbs on either extremity, in one order, which he proposed to call Cheiropoda, and these again into three sections. The first, having the opposable thumb on the hands only, included man, and was called Bimana. The second had the characteristic mark on both hands and feet, and was called Quadrumana, including all the old world monkeys and the Lemurida. The third had it on the feet alone, and was named Pedimana, and included the monkeys of the new world, and another family which indeed possess this character, but which few would be hardy enough to class with Simiæ; I mean the Didelphide or Opossums. Thus, in this fantastic arrangement, old and new world monkeys are separated by aberrant Lemurs ; and placental and non-placental animals are mixed up in inextricable confusion. Moreover, there is an old world genus (Colobus) which possesses no thumb at all on the anterior extremity; and as such an animal can hardly be said to have the anterior thumb opposable, it must take its place among the Pedimana of the new world, far away from its companions of the old. In the fifth edition of Lyell's Geology, it is stated that no fossil remains of Quadrumana had been discovered, even in the most superficial deposits; but since that time (1837), such remains have been found, both in Asia and in America. Messrs. Cautley and Falconer discovered in the Sewalik Hills of the Himalayan range, fragments of a gigantic Simian, among the bones of other animals; and in the basin of the |