OSTEOLOGY OF BIRDS 69 



divisions among the vertebrae take place. The parts of the last 

 vertebra, that became anchylosed with the pelvis, are easily made 

 out. Very minute interdiapophysial foramina may pierce this 

 region; others are but indicated by minute dots. Along the mid 

 region, the ilia rise above these fused vertebrae in sharp crests, 

 which crests in being produced backward form the outer margins 

 of these pelvic bones where they constitute the postacetabular sur- 

 face. 



The " ilioneural grooves " are closed in, but they exist as 

 capacious " ilioneural canals " beneath the ilia anteriorly. 



Each ilium has a rounded anterior border, which presents a 

 slightly raised emargination just within it. 



The preacetabular surface of the ilia is fully twice as long as the 

 postacetabular, and its superficies is also double in extent [fig. 28]. 

 In each hone the former surface, anteriorly, is first directed up- 

 ward and only slightly outward; as it passes backward it faces 

 almost directly outward, a direction which it maintains for the rest 

 of its extent. The postacetabular surfaces of the ilia are confined to 

 two elliptical areas, which roof over the ischiac foramen on either 

 side, and the direction of whose surfaces is upward. Upon lateral 

 view of the pelvis [fig. 25], we see a circular acetabulum with a very 

 deficient base, the periphery of the inner circle being but little 

 smaller than the outer rim of the cavity. 



The antitrochanter is long and narrow. The plane of the ischiac 

 foramen is directed downward, backward and outward, and this 

 aperture is completely overshadowed by the ilium. The ischiac area 

 is generally concave and triangular, the apex of the latter being 

 directed backward. 



Considerable interest attaches to the condition in which we find 

 the pubic bones in Circus. The anterior limit of one of these bones, 

 after it leaves the acetabulum, closes in the obdurator foramen quite 

 completely, but does not pass beyond. Then occurs an interval, be- 

 low the lower margin of the ischium, which in life is filled in by 

 ligament, that connects the floating part of the remainder of the 

 pubic bone behind. ' This latter piece is simply suspended from be- 

 neath the posterior angle of the ischium by ligament, not in any way 

 connected with the anterior limb of the pubic rod, except through 

 the means of the material mentioned [fig. 25]. I made many care- 

 ful examinations and dissections of this bone in Circus before I was 

 satisfied of what I saw, and that the condition existed as I have 

 described it. In F a 1 c o sparverius the connection between 



