The three specimens originally described, the tooth, the skull, and the femur, were found at different times in the same horizon, all imbedded in the same volcanic tufa, as indicated in figure 1, D. The tooth was found first, in September, 1891, in the left bank of the river, about a meter below the water level during the dry season, and twelve or fifteen meters below the plain in which the river had cut its bed. A month later, the skull was discovered, only a meter distant from the place where the tooth lay. In August, 1892, the femur also was found, about fifteen meters distant from the locality where the other specimens were imbedded. Later, in October of the same year, a second molar was obtained at a distance of not more than three meters from where the skull-cap was found, and in the direction of the place where the femur was dug out.
The fossils thus secured were all carefully investigated by Dr. Dubois, who regards them as representing a distinct species and genus, and also a new family, which he has named the Pithecanthropidæ, and distinguished mainly by the following characters:
Brain cavity absolutely larger, and, in proportion to the size of the body, much more capacious than in the Simiidæ, yet less so than in the Hominidæ. Capacity of the skull about two-thirds the average of that of man. Inclination of the nuchal surface of the occiput considerably greater than in the Simiidæ. Dentition, although retrogressive, still of the simian type. Femur equal in its dimensions to that of man, and like that adapted for walking in an upright position.
Of this skull, the upper portion alone is preserved, the line of fracture extending from the glabella backward irregularly to the occiput, which it divides somewhat below the upper nuchal line. The cranium seen from above is an elongated oval in outline, dolichocephalic; and is distinguished from that of other anthropoid apes by its large size and its higher arching in the coronal region, as shown below in figure 3. The greatest length from the glabella to the posterior projection of the occiput is 185mm. The greatest breadth is 130mm, and the smallest, behind the orbit, is 90mm. The cranium in its original condition must have been of somewhat larger dimensions. The upper surface of the skull is without ridges, and the sutures all appear to be obliterated.
This dolicocephalic skull, with an index of 70°, is readily distinguished from that of the Orang-utan, which is decidedly brachycephalic. The absence of the characteristic cranial crests will separate it from the skull of the adult Gorilla. In its smooth upper surface and general form, it shows a resemblance to the skull of the Chimpanzee, and still closer to that of the Gibbons (Hylobates).
