250 ALLEN’S NATURALIST’S LIBRARY. 
Besides these external characters, we find, on examining their 
bony structure, much variation in the skull. Some have a 
rounded forehead, the ascending portion of the lower jaw 
being high, broad, and flat, with a large facial angle ; in others, 
we have great production of the upper jaw (the horizontal part 
of the lower jaw being greater than the ascending portion), 
and a low facial angle. The cerebral portion of the skull is long 
and flattened, and the palate long and narrow. The dental 
formula is 13, C}, P3, M3 = 32, that of the milk-teeth IZ, C1, M 
(the forerunners of the permanent fve-molars) 3 = 20, exactly 
the same asina Man. ‘The outer lower incisors are equal to, 
or sometimes smaller than, the inner pair. The permanent 
canines—which are long and sharp— come in before, or with the 
posterior molars of both jaws. Between them and the incisors 
above, and between the canine and the anterior pre-molar be- 
low, occurs a gap (or diastema). ‘The anterior upper pre-molar 
has its outer cusp modified and sharpened; the anterior 
lower pre-molar has the anterior margin of its crown so shaped 
as to work “as a scissors’-blade against the posterior edge 
of the upper canines.” (/en/ey.) The crowns of the molar 
teeth are long from before backwards,.and their fore and 
hind cusps are united by transverse ridges, a third being 
present in the same genera, on the posterior lower five-cusped 
molar. 
The nasal bones are often ossified together to form one 
bone. The surface of the skull is in general oval and smooth, 
but in some of the Baboons there appear strong ridges over 
the eyes (hiding the forehead) and along the top of the head, 
being stronger, when present, in the male than in the female. 
The external orifice to the ear hasa considerable bony tube, or 
meatus, a distinguishing character which is absent in the New 
