COLUMBA 121 



In the lower jaw, Meckel's cartilage is represented by the 

 articular, and the angular, supra- angular, splenial, and dentary 

 are membrane-bones. 



The hyoid skeleton is represented dorsally by the columella 

 auris, connecting the ear-drum with the fenestra ovalis of the 

 auditory capsule, passing behind the quadrate. Ventrally, the 

 " hyoid " consists of basihyal, ceratohyal, basibranchial, and 

 ceratobranchial of the ist branchial arch. 



There are no teeth in the pigeon nor in any living 

 bird. 



Vertebral Column. — The first two vertebras are the atlas 

 and axis. They are followed by twelve others, forming the 

 cervical region of the vertebral column. The articulation of 

 the centra with one another is of a peculiar saddle-like pattern 

 called heterocoelous, and giving the neck great flexibility. 

 The vertebrae have neural arches, zygapophyses, extra articular 

 facets called hypapophyses, and transverse processes. The 

 ribs articulate with the vertebrae by two heads ; a dorsal 

 tuberculum (fitting on to the transverse process) and a ventral 

 capitulum (touching the centrum). None of the ribs of the 

 cervical vetebrae reach the sternum, and the first ten, carried 

 by vertebrae 3 to 12, are actually fused with their respective 

 vertebrae. In this manner, each of these vertebrae has a little 

 (vertebrarterial) canal on each side. Cervical ribs of vertebrae 

 13 and 14 are free. 



There are five thoracic vertebrae, of which the first four are 

 fused together, and the last is fused on to the next posterior 

 vertebra (ist lumbar). The thoracic ribs are jointed and are 

 attached ventrally to the sternum. All the free ribs except the 

 last bear processes (uncinate) which overlap the next posterior 

 rib, and help to give strength to the thoracic box. 



The lumbar vertebrae are six in number, and they are fused 

 in front with the last thoracic, and behind with the two sacral 

 vertebrae, and the first five caudals. In this way an extensive 

 sacrum is formed, to which the ilia of the pelvic girdle are 

 attached, strong enough to stand the leverage on the ilia due 

 to the horizontal position of the bird's body with the legs at 

 the hind end. 



