596 SHUFELDT—OSTEOLOGY OF THE STRIGES. [Dee. 7, 
Parapophyses of that vertebra which is opposite the acetabula are 
prominent, they being long and ample, reaching to the border and 
reinforcing that part of the pelvis that requires it the most, the 
vicinity of the leverage for the pelvic limbs. In other Strig¢de 
several apophyses are thrown out at this point. The posterior 
opening of the neural canal in the last sacral vertebra is subcircular, 
its diameter being about a millimetre in length. This vertebra also 
possesses small postzygapophyses, looking upward and outward for 
articulation with the prezygapophyses of the first coccygeal vertebra ; 
the articulating facet of the centrum is also small, long trans- 
versely, notched in the median line, the surface on either side 
being convex, Atevery point where the sacrum meets the iliac 
bones union is firm and complete, though both upon the internal 
and external surfaces the sutural traces are permanently apparent. 
The anterior iliac margins, as they diverge from the sacral spine, 
form an acute angle, concave forward ; they have a well-marked 
rim or border, nearly a millimetre in width, raised above the gen- 
eral surface of the bone, which disappears on the outer borders as we 
follow them backward. The two anterior and outer angles overhang 
the sacral pair of ribs and fifth or last dorsal pair. From these last 
the marginal boundaries, which necessarily give the bones their 
form, are produced backward and outward to a point opposite the 
centrum of the third sacral vertebra, then backward and inward, 
forming at the above points two lateral angles. From the apices of 
the two lateral angles to where the borders terminate on either 
side in front of the acetabula with the pubic bones, the direction is 
such as to form a concavity on each side; the line adjoining the 
bases of these concavities, points opposite the posterior openings of 
the ilio-neural canals, being the narrowest part of the pelvis. The 
upper and at the same time the inner margins of the bones in ques- 
tion form the anterior and median angle at first approach, soon to 
diverge from each other and form the gluteal ridges and borders 
of those scale-like projections of the posterior portion of the ilia 
that overhangs the acetabula. Produced now as the “gluteal 
ridges,’’ they tend almost directly backward, though very slightly 
inward, to terminate in the ischial margins. ‘The preacetabular 
dorsal iliac surfaces are generally concave, while the postacetabu- 
lar, and at the same time that surface which occupies the higher 
plane, is flat, having a slope downward and backward, with a ven- 
tral reduplication after forming the rounded and concave posterior 
