358 MR. R. OWEN ON THE OSTEOLOGY OF 
and Chimpanzee. In the latter animal this obliteration takes place at a very early pe- 
riod, some time at least before the temporary teeth are shed; whilst in the Orang the 
sutures remain until the permanent teeth are almost fully developed. In the human 
subject the inter-maxillary bones can be traced as distinct elements of the jaw only at 
the early periods of fetal existence. 
The os nasi of the Orang is a flattened elongated triangular bone, no part of which 
projects, as in the Chimpanzee, beyond the plane of the nasal processes of the superior 
maxillary bones; there are no traces of its being originally separated at the me- 
sial line, while such are usually observable in the Chimpanzee. Dr. Traill, indeed, 
found two distinct nasal bones in the young animal of that species dissected by him!. 
In the Orang a strong spine or ridge extends from the posterior aspect of the os nasi 
down the middle line. 
The whole outer boundary of the orbit has a more anterior aspect than in the Chim- 
panzee: it is relatively broader and stronger, but has the oblique posterior ridge less 
developed. The interorbital space is relatively narrower ; and this difference between 
the Orang and Chimpanzee is naturally greater in the young state, before the upper 
maxillary bones have acquired their full development?. In this particular, again, the 
Orang recedes further from the human form. 
The lachrymal bones are proportionally larger in the Orang than in Man; but, as 
1 Wernerian Transactions, vol. iii. p. 12. 
* With respect to the difference in the proportions of the orbits in the young Orang and the Pongo, the same 
argument to prove a difference of species might be drawn from a comparison of the orbits of a child’s skull of four 
years, and those of an adult human subject, which do not differ more than 2 lines, and in some instances not 
more than 1, in either the transverse or vertical diameter; and a similar proportional magnitude of the orbits 
prevails in the young of most Mammalia. The ingenious observation, however, made by Dr. Harwood (Lin- 
nean Transactions, vol. xv. p. 478.) on the difference in the breadth of the interorbital space, would be appa- 
rently borne out by contrasting some skulls of the young and adult Orangs, since it is not always the same in 
animals of the same age: but I apprehend that the difference between the young and adults in this respect may 
be accounted for by the increase of size which the nasal processes and every other part of the superior maxil- 
lary bones undergo after the development of the great Janiarii, it being remembered that the cavities of the 
orbits do not increase in the same ratio. Having had the opportunity of comparing six crania of the young 
Orang with two of the Pongo, I find the interorbital space of 24 lines to be the minimum in the former, and 
that of half the breadth of the orbit to be the maximum in the latter, among the individual varieties. 
Young Orang. Pongo. 
in. lines. in. lines. 
Breadth of the face taken at the fronto-malar sutures . . . 2 10 4 a6 
Breadth Gitthetarniay ee. Acswil? Me ee ER ee aN SRS hy 16 
Interorbital space taken across the fronto-maxillary suture. 3 7+ 
To determine the degree of difference which existed in the planes of the orbits of the young Orang and Pongo, 
I drew a line from the anterior part of the auditory foramen through the part where the sagittal joins the co- 
ronal suture, and intersected it by another drawn from the lower part of the orbit across its plane. In this 
way a difference in the plane of the orbit is found to manifest itself in the skulls of specimens of the immature 
Simia Satyrus of different ages and of acknowledged identity of species, the angle becoming more open in the 
older specimens; whilst in the great Pongo the difference in the angle is not more than four degrees. 
