AXTAL SKELETON OF THE OSTRICH. 433 
part of what may be fancifully compared to a bird’s skull, while the same margin of 
the postacetabular part of the ilium forms the apparent upper margin of the beak of 
such a skull, the whole (straight) inferior margin being formed by the ventral surface 
of the sacrum. 
The ventrally proceeding osseous bars (the pubis and ischium) join in an expansion (7) 
situated ventrally to and opposite the postaxial end of the sacrum. 
Beyond this point the pubis curves backwards, and then sharply first downwards (sy) 
and then forwards, its preaxial extremity advancing a little preaxiad of the extreme 
point to which the whole sacrum extends postaxiad. 
The obturator foramen is very elongated, and is divided into a very small anterior 
and a very larger posterior portion by a process (ps) of the ischium which joins the 
pubis a little behind the acetabulum. 
The pubis, at its junction with the ilium, developes a strongly projecting, curved and 
pointed ilio-pectineal process (/p). Sometimes a small process projects from the middle 
of the ventral margin of the pubis. 
LATERAL ASPECT OF PELVIS (4 natural size). 
Fig. 71. 
Letters as last, except [p, ilio-pectineal process, and ps, process of ischium dividing off the small anterior part 
of the elongated obturator foramen. 
The extreme pre- and postaxial extent of the pelvis is almost double its greatest dorso 
ventral dimension. 
When the pelvis is viewed dorsally (fig. 72) we see in the middle of its preaxial third 
the dorsal iliac median ridge, and on each side the concave external margins of the ilia, 
with the two sacral ribs ( p/) protruding, one on each side, from the more preaxial part 
of those margins. At about the middle third of the total pre- and postaxial diameter 
of the pelvis the antitrochanteric processes (at) stand sharply outwards. Behind a 
transverse line joining these processes we have five elongated pieces of bone, the middle 
VOL, VIII.—PART vil. March, 1874. 3P 
