Hip bone each other at the pubic symphysis. Together with the sacrum and coccyx, the hip bones form the pelvis. Ilium (plural "ilia") is the uppermost and largest region. It makes up two fifths of the acetabulum. It is divisible into two parts: the body and the ala or wing of ilium; the separation is indicated on the top surface by a curved line, the arcuate line, and on the external surface by the margin of the acetabulum. The body of ilium forms the sacroiliac joint with the sacrum. The edge of the wing of ilium forms the S-shaped iliac crest which
Body of sphenoid bone groove, in the angle between the body and greater wing, is a ridge of bone, called the sphenoidal lingula. The posterior surface, quadrilateral in form [Fig. 3], is joined, during infancy and adolescence, to the basilar part of the occipital bone by a plate of cartilage. Between the eighteenth and twenty-fifth years this becomes ossified, ossification commencing above and extending downward. The anterior surface of the body [Fig. 2] presents, in the middle line, a vertical crest, the sphenoidal crest, which articulates with the perpendicular plate of the ethmoid, and forms part of the nasal septum. On either side of