XII 



PHYLUM CHORDATA 



463 



CtCT? 



out at right angles to the trunk, twenty-three large feathers 

 (Fig. 273) are seen to spring from its hinder or post-axial 

 border': these are the remiges or wing-quills. Twelve of 

 them are connected with the ulna and are called cubitals 

 or secondaries (cb. rmg) . The rest are known as primaries. 

 In the tail there are twelve long rectrices {ret) or tail-quills 

 springing in a semicircle from the uropygium. The whole 

 feather-arrangement is known^as the pterylosis. 



f. trs 



$cb 



FIG. 276. Columba livia. The bones of the trunk, acr. cor, acrocoracoid ; 

 a. tr, anti-trochanter; actb, acetabulum; car, carina sterni; cd. v, caudal verte- 

 brae; cor, coracoid; cv. r, cervical ribs; _/ trs, probe passed into foramen 

 triosseum; fur, furcula; gl. cv, glenoid cavity; z7, ilium; is, ischium; is. for, 

 ischiatic foramen; obt. n, obturator notch; pu, pubis; pyg. st, pygostyle; scp. 

 scapula; s. scr, syn-sacrum; st, sternum; st. r, sternal ribs; th. -v. I, first, and 

 th. v. 3, last thoracic vertebra; unc, uncinates; vr. r, vertebral ribs. 



The vertebral column is distinguished from that of most 

 other Craniata by the great length and extreme mobility of 

 the neck, the rigidity of the trunk region, and the shortness 

 of the tail. There are fourteen cervical vertebrae, the last 

 two of which have double-headed ribs (Fig. 276,^. r) each 



