( 528 ) 
Lissauer ’), running from the protuberantia occipitalis externa to the 
point where the ala of the vomer is joined to the rostrum sphenoidalis. 
By the method I have adopted in determining the slope of the 
For. magn. I have proceeded from the base-line which was described 
m the first paper, and in so-doing have answered the question as 
to what angle is made by the plane of the occipital foramen with 
this line. To express this angle in all Primates always as a positive 
value it is not possible to measure the angle directly. For in the 
Primates 3 conditions occur: a. the opisthion lies higher than the 
basion, the For. magn. looks backwards, and the angle is therefore 
an acute one closed at the back; b. basion and opisthion lie at equal 
distances from the base-line, the For. magn. looks downward, is 
parallel to the base-line, and the angle = 0 ; c. the basion lies higher 
than the opisthion, the For. magn. looks forward and the angle is 
an acute one closed in front. To prevent confusion between angles 
of equal size in cases a and c, a + or - sign could be used. I 
think, however, the variations in the inclination might be represented 
more simply in determining the angle made by the plane of the 
For. magn. with a perpendicular drawn from the basion to the 
base-hne. In case a this angle is always acute, in case b it is a 
right angle, and in case c it is an obtuse angle. 
In Fig. 1 this method is clearly seen on the mediagram of an 
Ateles skull. The following table gives the results of the researches 
on the skulls of full-grown monkeys. 
f 4 ®°*f suclmn S“ “ber die sagittale Krummung des Schddels. Arch, 
f. Authrop. XV Bnd. Suppl. 
