306 



PROF. HUXLEY ON THE ALECTOROMORPH^. [May 14, 



nineteenth bears ribs which are nearly as long as those of the first 

 dorsal and possess very deep, though short, unciform processes. On 

 the right side, the rib of this vertebra is connected with the sternum 

 by an incompletely ossified sternal rib. 



The vertebral ribs of the dorsal region are remarkably broad ; and 

 in the three anterior pairs a considerable extent of the posterior 

 margin is occu])ied by the unciform process, which is always shorter 

 than the intercostal space. 



In the breadth of the ribs, and depth and relative shortness of 

 the unciform processes, the ordinary Pigeons come nearest Opistho- 

 comus. The ribs of Corythaix have a totally different character. 



Fig. 8, front, and Fig. 9, side view, of the sternum and shoulder-girdle of 

 Opisthocqmtcs cristatus. 



The sternum, as several observers have already pointed out, is 

 one of the most anomalous parts of the organization of Opisthoco- 

 Its lateral edges remain nearly parallel for about two-thirds 



mus. 



of its length, and then diverge, causing the transverse diameter to be 

 considerably wider posteriorly than anteriorly. The external xiphoid 

 processes are but little shorter than the middle xiphoid ; and the 

 posterior edge is evenly curved backwards. It pi'esents two notches, 

 of which the outer pair may be converted into foramina. The iimer 

 pair fffe deeper than the outer, but do not extend for a sixth of the 



