20 Osteology of Circus hudsonius. 
notched anteriorily. The common top of this neural spine for 
nearly the entire length of the pelvis is smooth, and presents 
little or nothing to indicate where the divisions among the vertebrae 
take place. The parts of the last vertebra, that became anchy- 
losed with the pelvis, are easily made out. Very minute inter- 
‘diapophysial foramina may pierce this region ; others are but indi- 
cated by minute dots. Along the mid-region, the ilia rise above 
these fused vertebree in sharp crests, which crests in being produced 
backwards form the outer margins of these pelvic bones where they 
constitute the postacetabular surface. 
The ‘‘ilio:neural grooves’ are closed in, but they exist aS 
capacious ‘‘ilio-neural canals’’ beneath the ilia anteriorly. 
Each ilium has a rounded anterior border, which presents 2 
slightly raised emargination just within it. 
The pre-acetabular surface of the ilia is fully twice as long as 
the post-acetabular, and its superficies is also double in extent. 
(Fig. 10). In each bone the former surface, anteriorly, is first 
directed upwards and only slightly outwards, as it passes back- 
wards it faces almost directly outwards, a direction which it main- 
tains for the rest of its extent. The post-acetabular surfaces of the 
ilia are confined to two elliptical areas, which roof over the 
ischiadic foramen on either side, and the direction of whose sur- 
faces is upwards. Upon lateral view of the pelvis (Fig. 7), weseea 
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 anti-trochanter is long and narrow. ‘The plane of the 
ischiadic foramen is directed downwards, backwards and outwards, 
and this aperture is completely ovsrshadowed by the ilium. The 
ischiadic area is generally concave and triangular, the apex of the 
latter being directed backwards. 
Considerable interest attaches to the condition in which we find 
the pubic bones in Czvcus. ‘The anterior limit of one of these 
bones, after it leaves the acetabulum, closes in the obturator 
foramen quite completely, but does not pass beyond. ‘Then 
occurs an interval, below 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 beneath 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 
