390 A HISTORY OF BIRDS 



inasmuch as it is found with especial frequency among the 

 small and more primitive forms. 



It is, however, among the vegetivorous types, as we have 

 already remarked, where the food is only to be obtained by 

 laboriously quartering the ground on foot, that the most con- 

 spicuously broad pelvis obtains. 



Two of the most striking instances of this are to be found 

 in a Cuckoo known as the Chapparal Cock or American Road 

 Runner {Geococcyx) and a Grouse, the Prairie-hen {Tynipanu- 

 cJms). Displaying a remarkable similarity in some respects, 

 they differ materially in others. In the Grouse the post- 

 acetabular region of the ilium is enormously expanded so as to 

 be as wide as the whole length of the pelvis, while it extends 

 outwards and downwards on either side as a huge shelf over- 

 hanging the ischium, to an extent elsewhere unknown. In con- 

 trast with the majority of the Galli the pectineal process is 

 conspicuous by its absence, and this fact is noteworthy. 



In the Cuckoo (Geococcyx) the post-acetabular ilium, as may 

 be seen in 111. 42, is also extremely broad. It differs, however, 

 from this region in the Grouse just described in that it turns 

 first downwards, then upwards and backwards to form a cavern- 

 ous space above the ischium, and in so doing effects the same 

 purpose as the wholly downward growth in the Grouse — to wit, 

 it affords increased surface for the attachment of the muscles of 

 the leg. The pectineal process is here strongly developed. In 

 both these birds the pubis is degenerate. The presence of the 

 pectineal process is a feature of considerable importance, and 

 is generally regarded as indicative of well-developed running 

 powers, which are conspicuously developed in the Cuckoo — 

 hence the name " road-runner ". Indeed it is more expert at 

 this form of locomotion than at flight, the wings being short 

 and rounded. 



But there are many puzzling exceptions to this rule, associa- 

 ting broad pelves with great powers of walking and running. 



In the first place, there are many birds which have 

 strikingly broad pelves though neither walking nor certainly 

 running play any very conspicuous part in their life-history. 

 Thus the Osprey {Pandion) differs from all the other Accipitrine 

 birds in the great width of its pelvis. This fact might be 

 attributed to the need of great muscular strength for raising 



