432 MR. ST. GEORGE MIVART ON THE 
Within the line of these ribs is to be seen a very large ventral arch, each side or 
lateral half of which is bent at an angle into a dorsal and ventral division or limb, which, 
when viewed preaxially, appears as follows :— 
The dorsal division, or limb, consists mainly of the pubic bone (p), which diverges from 
its fellow of the opposite side at an angle of about 66°. The external margin of this 
limb is, in the main, concave externally ; but the outline is interrupted by the more 
distant jutting out of the posterior part (é) of the ischium. The internal margin of the 
dorsal limb is convex, but with its outline interrupted, and the convexity exaggerated 
by the projecting inwards (7) of the more anterior part of the ischium. 
The ventral division or limb is bent inwards on the dorsal limb (of the same half of 
the great ventral arch) at an angle of about 115°, and consists of the pubis, which ter- 
minates ventrally by meeting its fellow in (sy) a ventral symphysis. 
The external margin of this ventral division is concave ; its internal margin is convex. 
When the pelvis is viewed postaxially the same great ventral arch is seen to be con- 
nected dorsally with a pentagonal mass, one angle of which is dorsad, and which has in 
its midst the postaxial surface of the small twenty-second sacral vertebra, @. e. the forty- 
seventh vertebra of the whole spinal column. 
The two dorsal sides of the pentagon meet at an angle of about 118°; and the margin 
of each, from the point of junction outwards, is slightly concave, then more strongly 
convex, then still more sharply concave, the sharp concavity being produced by the pro- 
minence of the antitrochanteric process. Each of these dorsal sides is formed by an 
ilium. 
From the tip of this last-mentioned process each lateral margin of the pentagon pro- 
ceeds ventrad, forming with the adjacent dorsal side an angle of about 90°; its margin 
is, for its greater part, gently concave, and is formed by the ischium ; it forms with the 
ventral side of the pentagon an angle of about 120°. 
This ventral side of the pentagon is formed by the pubes, and is more or less 
horizontal. 
When the pelvis is viewed Jaterally (fig. 71), the sacrum being horizontal, we have a 
dorsal elongated mass (made up of the ilium and sacrum) something like the skull of a 
bird, with the tip of the beak turned postaxially, from which two long bars of bone 
(¢ & p) diverge ventrally and proceed postaxiad to join and end in a great recurved 
process (s 7). 
These bars proceed from beneath the acetabulum. 
The acetabulum is placed on the ventral side of the ilio-sacral mass, so that its postaxial 
margin is on the preaxial side of the middle point of that elongated mass. 
Within the acetabulum are to be seen the four slender, dorsally and preaxially 
extended diapophyses of the thirty-second, thirty-third, thirty-fourth, and thirty-fifth 
vertebre. 
The dorsal margin of the preacetabular part of the ilium forms the roof of the cranial 
