THE PIGEON. 187 



rib, having all the characters of the last cervical rib ( 14, 

 15), a ventral section, the sternal rib, a straight flat 

 bone, making an obtuse angle with the vertebral rib, and 

 articulating at its lower end with a facet on the sternum. 



tr.f" 



FIG. 46. Columba livia. The sacrum of a nestling (about fourteen 

 days old), viewed from beneath ( x 2). 



On the left side (right of the figure) the first two caudal ribs (c.r) are 

 removed, so as to show the dorsal transverse processes (tr.p") : the sub- 

 sequently ossifying membrane which fills up the intervals between the 

 transverse processes is also removed on the same side : the last thoracic 

 vertebra is not shown, not yet having united with the sacrum. 



The cartilaginous parts are dotted. 



c.i, ossified centrum of first, and c.*j, of seventh caudal vertebra: 

 c.r, first caudal rib: /.i, centrum of first, and /.3 of third lumbar 

 vertebra : s.i, centrum of first, and -$-.3 of third sacral vertebra : tr.p, 

 transverse process of first lumbar, tr.p', of second sacral, and tr.p", 

 of first caudal vertebra. 



VI. In the remaining vertebrae entering into the com- 

 position of the compound sacrum make out : 

 26. The two or three lumbar vertebrae (Fig. 46, /.i 

 /. 3), immediately succeeding the fifth thoracic : each has a 

 stout wide body, short strong transverse processes abutting 



