204 • N EW YORK STATE MUSEUM 



the Eustachian apertures are invariably double, the separate tubes, 

 in the skull, opening in that situation about a millimeter, or rather 

 more, apart. 



The mandible of the Sage cock is comparatively slender. The 

 rami are shallow, the ramal vacuities small, but the posterior angular 

 processes long and acute. 



Nothing especially peculiar characterizes the chain of vertebrae 

 in this large fowl, and in a former memoir I presented a drawing 

 of the massive consolidated dorsal vertebrae. 



The pelvis is remarkably broad, capacious [pi. 7, fig. 31], and 

 at the same time compressed in the vertical direction. Prepubic 

 spines are nearly aborted, while the postpubic ones are produced 

 behind, and somewhat expanded at their extremities. Viewed su- 

 periorly, the general pattern of the pelvis in Centrocercus agrees 

 with that bone as we find it in the various species of Lagopus ; 

 and in this particular those genera seem to approach the genus 

 Canachites. Relatively, the body of the sternum in the Sage cock 

 is broad, but with its broad pelvis this is what we would naturally 

 look for, after the rule we have given above. Figures 53, 54 

 and 56 of my Hayden Survey memoirs show very well the method 

 of development of the sternum in Centrocercus, from several ossific 

 centers, a method of development which holds true for this bone 

 throughout the typical gallinaceous series. Later on ossific centers 

 appear in the expanded posterior ends of the xiphoidal prolonga- 

 tions, and these are duly exhibited in the aforesaid figures. In the 

 chick of Centrocercus, a few days old, the sternal body is nearly 

 circular, and the five centers of ossification eminently distinct ; and 

 the carina, thus far, is only preformed in bone anteriorly. During 

 the chick's life it dips well down between the tender pectoral 

 muscles. 



As further descriptive of this bone, I remarked in my earlier 

 memoir entitled Osteology of the North American Tetraonidae, 

 that the manubrium, now only in cartilage, has at this early date 

 110 evidence of the foramen that later joins the coracoidal grooves. 

 As to the rest, bands of delicate membranous tissue bind them 

 loosely together. The sternum in a bird of several months' growth 

 is, as I have already said, shown in figure 56 of my memoir above 

 cited. Here the bone is rapidly assuming the shape it is destined 

 to retain during later life. The body and with it the keel is ex- 

 tended by generous deposition of bone tissue at its margins, prin- 



