166 



PELVIS. 



from the coalesced transverse processes by 

 two faintly-marked longitudinal grooves. The 

 transverse processes of the true sacral ver- 

 tebrae present a very prominent framework 

 of ridges anteriorly (jig. 105.), which have a 

 direction upwards and backwards as well 

 as outwards, the most strongly marked 

 being opposite the acetabula (/>). They are 

 coalesced on the superior aspect, by a thin 

 plate of bone only. The sacrum, as seen from 

 above (jig. 104-.), has a diamond-shaped ap- 

 pearance, and is marked out from the iliac and 

 ischial elements by a faintly-marked suture 

 (c). The sacrum in Birds is a continuation of 

 the line of the great dorsal curvature. 



The coccyx is generally short, composed of 

 from five to nine pieces, generally perforated 

 for the spinal marrow, and curved dorsally, as 

 we have observed before in some Rodents, 

 terminating in a spinous-shaped piece (see jig. 

 107., a). 



The ilia are comparatively short and narrow : 

 with a very short cotylo-sacral rib or shaft (e), 

 directed upwards and forwards, and expanding 

 into a wing (d), concave or grooved supe- 

 riorly. The a/a is prolonged forwards on the 

 posterior surfaces of the ankylosed lumbar 

 vertebra?, coalescing with their spines and 

 transverse processes; and also extends back- 

 wards to a less degree, to coalesce with the 

 upper bifurcation of the anterior extremity 

 of the ischium, in a sort of buttress (f], which 

 projects externally anil overhangs the aceta- 

 bulum posteriorly, presenting, below, a facet, 

 against which rests the trochanter of the 

 femur, and which is apparently a continuation 

 of the articular cotyloid surface. This but- 

 tress is continued from the ischium inwards, 

 as a strong ridge, to the extremity of the 

 strongest of the sacral transverse processes 

 before mentioned (Jig. 105.6), opposite the 



Fig. 105. 



Inferior or ventral view of the pelvis of the Par- 

 tridge natural size : a, coalesced bodies of sacral 

 vertebrae ; b, sacral transverse processes ; n, ischial 

 spine ; r, lumbar or pseudo-sacral processes ; s, anky- 

 losed lumbar vertebra;. The remaining letters refer 

 to the same parts as in Jig. 99. 



lateral angles of the diamond-shaped sacral 

 plate, and evidently contributes in the greatest 



degree to support the trunk upon the femurs 

 in the standing posture. The principal part of 

 the ilium in birds is composed of the alee, 

 which lie almost altogether on the dorsal aspect 

 of the spinal column. The total axis of the 

 ilium, however, crosses that of the spine at an 

 angle of from 150 to 160, and does not, 

 strictly speaking, lie parallel to it, as is com- 

 monly asserted (see jig. 112. 10.). 



From the posterior part of the inner border 

 of the iliac wing passes backward a thin plate 

 of bone (g-), along the external borders of the 

 diamond-shaped sacral plate, from which it is 

 marked by a distinct line of suture (c). It is 

 continuous, posteriorly and externally, with the 

 sacro-sciatic ossification, to be presently men- 

 tioned, from which it is also marked, especially 

 in the Partridge and some other birds, by a 

 raised line of demarcation (t). This thin plate 

 is convex above and concave below, and enters 

 into the formation of the pelvic cavity, being 

 much hollowed in the Partridge and the Gal- 

 linacecs generally {jig. 105. g), to receive the 

 pelvic viscera. It seems to result from the 

 ossification of the sacro-iliac oblique ligament, 

 and to form a separate pelvic element which 

 may be called the sacro-iliac, or ilio-sacral. 



The ischia of birds (k) are long, strong, and 

 divergent posteriorly ; and, from the perfora- 

 tion of the cotyloids, appear to be bifurcated 

 at the anterior extremity. The inferior bifur- 

 cation is horizontal, coalesces with the ilium 

 and pubis, and separates the acetabulnm (i) 

 from the obturator foramen (o). The 

 superior bifurcation is vertical in direction, 

 separating the acetabulum (?) from the sacro- 

 sciatic foramen (/), and coalescing above, inter- 

 nally with the long sacral transverse process 

 (b) and ilio-sacral bone (g), and anteriorly 

 with the ilium in the ischio-sacral buttress (/), 

 before mentioned, which it principally con- 

 tributes to support and form, and which may be 

 considered as the homologue of the ischio-sacral 

 arch in the human pelvis, separated from the 

 cotylo-sacral rib (e) by a thin plate of bone 

 above, and by the perforated acetabulum 

 below. The posterior extremity of the ischium 

 is much elongated, and constitutes the bulk 

 of the bone. Its inferior border is spread 

 out into a broad thin plate, slightly prolonged 

 into an anterior process (>)> which seems 

 to represent the ascending ramus of Mammals, 

 from its frequently uniting with the pubis 

 and forming the posterior boundary of an 

 obturator foramen. 



Its superior border is prolonged into a 

 broad thin plate (//) hollowed out in the pelvic 

 cavity, and which constitutes the sacro-sciatic 

 pelvic element, being evidently formed by ossi- 

 fication of the sacro-sciatic ligaments, from its 

 completing posteriorly the sacro-sciatic foramen 

 (I), and coalescing with the sacro-iliac plate 

 (g), before mentioned, and, behind it, with the 

 sacrum. The posterior extremity of the 

 ischium is prolonged generally into a thin 

 angular spinous process (n). The iscliia in 

 Birds generally form a right line with the 

 ilia; but in the Birds of prey they constitute a, 

 remarkable exception, and make a very 



