GENERAL ORNITHOLOGY 



56, // 60, 61, 11) is the median, .most anterior and longest of 

 the haunch-bones, and the only one which extends in advance of 

 the acetabulum. Such anterior prolongation of this bone is the 

 specialty of the avian pelvis : it commonly overlies one or more 

 ribs, and is often overreached by the end of the scapula. It is 

 longest and narrowest and flattest in some of the lower swimmers; 

 the reverse among the highest birds. Its relations and connections 

 have been sufficiently indicated. The bone is almost always 

 separated from its fellow by the sacrum, though the approxima- 

 tion may be close over the back of the pelvis, along the middle line. 



The Ischium (Gr. la-ylov, ischion, the haunch-bone; pi. ischia; 

 adj. ischiadic, ischiatic, better ischiac ; Figs. 56, 60, 61, 7s) lies 

 entirely post-acetabular, or behind the socket which it contributes 

 to form, and composes most of the side-wall of the pelvis thence to 

 the end. It is generally a thin plate-like bone. Among Cretaceous 

 birds and existing Ratitm it only unites with the ilium at and just 

 behind the acetabulum, whence a deep ilio-ischiac fissure between 

 the two exists, as in the young grouse, Fig. 61 ; but in ordinary adult 

 birds this fissure is converted into a fenestra or window of large 

 size, just behind the acetabulum, by union of the two bones behind 

 it. This vacuity, whether a notch or a hole, corresponds to the 

 " sacro-sciatic notch " of human anatomy (Fig. 56, in). The ischia of 

 opposite sides are distinct, .except in Rhea. 



The Pubis (Lat. pubis, bone of the front of the human pelvis where 

 the hair grows at puberty ; pi. pabes ; adj. 'pulic : Figs. 50, 60, 61, F), 

 beginning at its share of the acetabular ring, is a long slender bone 

 which runs along the lower border of the ischium, sometimes for a 

 short distance only, often for the whole length of theischium, and usually 

 projecting behind ; more or less perfectly parallel with, applied to, 

 or united with, the inferior ischiac border. When separate, a long 

 deep fissure results ; when united at the end, a long narrow foramen 

 is formed; when incompletely united in any part of its ischiac 

 continuity, a fissure and a foramen, in the ostrich two foramina, 

 result. All these conditions occur ; in any case, such ischio-pubic 

 interval corresponds to the dbtvtrator foramen (Fig. 56, 0/ Fig. 60, oJ) 

 of human anatomy ; it is greatest in Cretaceous birds and existing 

 Batitm. The free ends of the pubes may be more or less expanded. 

 In the ostrich only there is a pubic symphysis of the ends of the 

 bones ; in the same bird a separate ossicle, situated upon the lower 

 border of the pubes, and called epipubic, is considered to represent 

 a " marsupial " bone (Garrod). In various birds, among them the 

 ground cuckoo, Geococcyx californianus, the pubis projects a little 

 forward, under the acetabulum : this prominence is the propubis. 

 Separation of the pubes is supposed to be for amplification of the 

 pelvic strait to facilitate the passage of the large eggs birds lay. 



