GENERAL CHARACTERISTICS 



Birds both jaws are incased in horn, and are devoid of teeth; while the two halves 

 of the lower jaw are completely soldered together by bone at their junction, or 

 symphysis. Certain extinct Birds had, however, a full series of teeth, and the two 

 halves of the lower jaw separate. 



As regards the backbone, existing Birds differ from Mammals in that the 

 bodies of the vertebrae, at least in the region of the neck, are articulated to one 

 another by saddle-shaped surfaces, instead of by a cup-and-ball joint or two nearly 



ANTERIOR ASPECT OF THE DORSAI, VERTEBRA OF A MOA (Pachyornis) . 



ns. upper or neural spine ; n. neural canal ; pz. prezygapophysis ; d. transverse process ; v. pedicle of arch ; 

 p. facet for rib ; ac. anterior surface of body or centrum ; hy. lower or haemal spine. After Owen. 



flat surfaces; and there is no constancy in the number of joints in the neck. 

 A further peculiarity is that a number of the vertebrae of the back, together with 

 some of those of the tail, are solidly united with the proper sacrum, while the 

 whole long series of welded vertebrae are themselves as firmly attached to the 

 haunch bones of the pelvis. In all living Birds the bones of the tail are very few 

 in number, and terminate in a triangular bone (as seen in our figure of the skeleton 

 of a parrot), termed the plowshare bone. It is to this region of the body that the 

 tail feathers of a bird, commonly called the tail, are attached, and it will thus be 



