AXIAL SKELETON OF THE OSTRICH. 431 
traces of diapophysial and parapophysial prominences. The neural spine is more or 
less trifid at its distal end (fig. 68, ns). 
The postaxial surface of the centrum is decidedly concave. 
The vertebra often becomes anchylosed with the next and last, both by its centrum 
and the distal portion of its spine. 
Tue Firry-sixrh VERTEBRA. 
This vertebra has no neural arch and no transverse process (fig. 69). 
It is a dorso-ventrally extended lamina of bone, extremely compressed laterally, with 
a very irregular, generally more or less rounded, margin dorsally, ventrally, and post- 
axially. It often anchyloses with the preceding vertebra at the dorsal and ventral parts 
of its preaxial surface, or rather margin, thus producing a foramen which looks from 
side to side. 
The existence of another (but minute) foramen placed postaxially to that just 
described may indicate that this bone really consists of two or more vertebra fused and 
anchylosed into one osseous mass. 
Sometimes a little bridge of bone (fig. 69, d) connects its centrum, laterally, with the 
centrum of the fifty-fifth, or ninth caudal, vertebra. 
THE PELVIS. 
This enormous bone consists of no less than twenty-two vertebra, more or less com- 
pletely anchylosed together (in the adult), and with the two ossa innominata, which latter 
thus cannot conveniently be excluded from the description of the axial skeleton. 
Preaxially the sacrum exhibits the preaxial surface of the first sacral vertebra (with 
characters corresponding with the vertebra naturally preaxiad to it) roofed over by the 
PREAXIAL ASPECT OF PELVIS (2 natural size). 
Fig. 70. 
at, antitrochanteric process; ¢ and ?’,ischium ; ¢/, ilium; p, pubis; pl, rib; s, spinous process of postanterior 
vertebrae ; sy, pubic symphysis. 
two iliac bones (7), which meet together over the dorsal end of its spine and diverge 
ventrad at an angle of about 63°—the two diverging lines being carried on by the two 
anchylosed ribs (p/) of the first sacral vertebra. 
