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the acetabulum the outer surface of the ilium is divided into two facets, 

 the upper one nearly horizontal, the lower one vertical, save where it 

 arches out to the flat articular surface behind the acetabulum. The ridge 

 dividing these two facets commences anteriorly above the middle of the 

 acetabulum, and describes a regular curve in its course backwards, the 

 convexity being downwards : in the Ostrich the corresponding ridge 

 forms two curves, meeting at an angle above the prominent articular 

 surface behind the acetabulum, and the convexity of both curves is up- 

 wards ; from the angle an obsolete ridge extends down to the prominent 

 articulation, and divides the anterior from the posterior vertically concave 

 surfaces of the ilium : in the great Dinornis the corresponding surfaces 

 are uninterruptedly continuous above the acetabular prominence. The 

 posterior wall of the acetabulum is incomplete, as in other birds ; the 

 smooth articular surface is continued upon an oblong prominence above 

 and behind the cavity. The pubis, a slender bone, as usual in birds, 

 springs from a protuberance at the lower part of the acetabulum. The 

 ischium is continued more directly from the lower and back part of the 

 cavity : a very slight ridge indicates the posterior boundary of the notch 

 for the tendon of the obturator internus, and the upper border of the 

 notch is nearly straight. In the Ostrich this part is concave, and a well- 

 developed process extends down, but does not join the pubis at the back 

 part of the obturator notch. The Apteryx resembles the great Dinornis 

 in this part of the pelvis. The ischium becomes compressed and gra- 

 dually expands vertically as it extends backwards, its lower margin form- 

 ing almost a straight line. In the Ostrich the ischium maintains its tri- 

 hedral form for a much longer extent and suddenly expands, the lower 

 margin curving down to join the pubis : there is no indication of such a 

 junction in the present specimen, nor does the superincumbent ilium 

 curve down, as in the Bustard, to join the ischium : both the ischiadic 

 and the obturator notches seem to have been unclosed by bone in the 

 Dinornis as in the Apteryx. 

 1560. This is a part of the right os innominatum, including the posterior and 

 inferior angle of the acetabulum, the origins of the pubis and ischium, 

 which form the obturator notch, and a fractured continuation of the 



